CHEMISTRY

Conclusion

Task 1.

Gaseous substances are given: H2, HCl, CO2, CO, O2, NH3.

1. Determine which of them are lighter than air and which are heavier (justify the answer).

2. Determine which of them cannot be collected by water displacement.

3. Determine what will happen to these gases if they are passed through a solution of acid, alkali (confirm the answer with the reaction equations).

Decision.

1. Lighter than air, those whose molar mass is less than 29 g / mol (molar mass of air). This is H 2 , CO , NH 3 . Heavier: HCl, CO 2 , O 2 .

2. The water displacement method can collect gases that are insoluble or poorly soluble in water. This is H 2 , CO 2 , CO , O 2 . It is impossible to collect gases by displacement of water: HCl, NH3.

3. Substances with basic properties react with acids:

NH 3 + HCl = NH 4 Cl

Substances with acidic properties react with alkalis:

HCl + KOH = KCl + H2O

Esep 1.

Gas tarizdі zattar berіlgen: H2, HCl, CO2, CO, O2, NH3.

1.Olardyn kaysysy auadan auyr zhane kaysysy zhenіl ekenіn anyқtaңyzdar (zhauaptaryңyzdy deleldenіzder).

2. Olardyn kaysysyn courts ygystyru adіsimen anyktauga bolmaytynyn anyktanyzdar.

3. Yeger olardy sіltinіn, қyshқyldyң erіtіndіlerі аrkyly өtkіzgende osy gazdarmen ne bolatynyn anyktaңyzdar (zhauaptaryңyzdy reaction teңdeuleri ақылідідінізтер).

Sheshui.

1. Auadan zhenil, yagni molyarlyk massasy 29 g/moldan (auanyn molyarlyk massasy) kishi bolatyn gasdar: H2, CO, NH3. Auyr: HCl, CO2, O2.

2. Courts of yғgystyru adіsimen of the court of erіmeitіn nemese of the court of az eritіn gazdardy aluga bolady. Olar This is H2, CO2, CO, O2. Courts ygystyru adіsi arkyly zhinauga bolmaityn gazdar: HCl, NH3.

3. Қyshқylmen negіzdіk қasiet korsetetіn zattar аrekettesedі:

NH3 + HCl = NH4Cl

Sіltіlermen қyshқyldyқ қasiet kөrsetetіn zattar аrekettesedі:

HCl + KOH = KCl + H2O

CO2 + 2KOH = K2CO3 + H2O or CO2 + KOH = KHCO3

Task 2.

In early spring, early in the morning, when the ambient temperature was still 0 ° C, and the pressure was 760 mm Hg. Art., three comrades, walking their dogs, saw an empty bottle on the lawn. "It's empty," one of them said. "No, it's full to the brim, and I know the formula of the stuff it's filled with," said another. "You're both wrong," said the third.

1. Which of the comrades, in your opinion, was right (justify the answer)?

2. Calculate the amount of substance and the number of particles contained in the bottle if its volume is 0.7 dm3.

3. Calculate the molar mass of the gas contained in the bottle.

Decision.

1. The third one is right, because there is air in the bottle (it is not empty - the first one is wrong), and the air is not an individual substance (the second one is also wrong). Air is a mixture of gases:

2. Since the conditions are normal, thenV M = 22.4 l/mol. Calculate the amount of substancen = V / V M \u003d 0.7 / 22.4 l / mol \u003d 0.03125 mol. Number of particlesN = N A n\u003d 6.02 1023 mol-1 0.03125 mol \u003d 1.88 1022 particles.

3. The molar mass of air can be calculated by knowing the composition of the air. Air contains approximately 78% N 2 , 21% O 2 , 0.5% Ar and 0.5% CO 2 . The average molar mass will be equal toM cf = x one · M 1 + x 2 · M 2 + x 3 · M 3 + x 4 · M 4

Esep 2.

Erte koktemde tanerten erte korshagan ortanyn temperature sy 0 °C, kysym 760 mm son. bug. bolyp turgan kezde ush adam ozderinin ytterin kydyrtuғa shykty zhane olar gazondagy bos құtyny (bottle) kөrdі. "Ol boss" - grandfather onyn bireui. “Joq, auzina deyin zattarmen toly” grandfather ekіnshіsi, sebi ol құtynyң ishіndegі zattardyn formulyasyn bіladі. "Sender ekeulerin de durys tappadyndar" - grandfather ushіnshіsi.

1. Sіzderdin oylaryңyzsha, osy үsh adamnyn kaysysy dұrys oilady (zhauaptaryңdy deleldenger)?

2. Yeger құtynyn (butylkanyң) ishіndegі zattyң kolemi 0.7 dm3 - he ten bolatyn belgili bolsa, zat molsherin zhane molecularlar sanyn tabynyzdar.

3. Kutynyn ishindegi gazdyn molyarlyk massasyn eseptenіzder.

Sheshui.

1. Ushіnshi adam durys aitty, sebebі onynіshіnde aua bar (ol bos emes, endeshe birinshi adam durys tappady), al aua zheke zat emes (sol sebeptі ekіnshi adam da durys tappady). Aua birneshe gazdardyn kospasynan turady: N 2, O 2, Ar, CO 2, H 2 O, etc.

2. Yagni zhagday kalypty, endesheV M = 22.4 l/mol. Zat molsherin esepteymizn = V / V M \u003d 0.7 / 22.4 l / mol \u003d 0.03125 mol. sana moleculeN = N A n = 6,02 1023 mol-1 0.03125 mol = 1.88 1022 bolik.

3. Auanyn kuramyn bile otyryp auanyn molyarlyk massasyn esepteuge bolady. Aua shamamen tomendegi gazdar cospasynan turady: 78% N 2, 21% O 2, 0.5% Ar and 0.5% CO 2 . Ortasha molyarlyk massas ten boladasM cf = x one · M 1 + x 2 · M 2 + x 3 · M 3 + x 4 · M 4 = 0.78 28 + 0.21 32 + 0.05 40 + 0.05 44 ≈ 29 g/mol.

Task 3.

You have calcium carbonate and hydrochloric acid at your disposal. Suggest methods for the synthesis of at least 6 new substances, including 2 simple ones. Syntheses can only use the starting materials, their interaction products, the necessary catalysts, and electricity.

Decision.

1. CaCO 3 \u003d CaO + CO 2 (when heated)

2.

3.

4. CaO + H2O = Ca(OH)2

5. CaCl 2 \u003d Ca + Cl 2 (melt electrolysis)

6. 2 HCl \u003d H 2 + Cl 2 (solution electrolysis)

7. 2H2O = 2H2 + O2 (electrolysis)

8. Ca + H2 = CaH2

9. Ca(OH)2 + Cl2 = CaOCl2 + H2O (at 0ºC)

10. when heated)

11. Cl2 + H2O = HCl + HClO (at 0ºC)

12. 3 Cl 2 + 3 H 2 O \u003d 5 HCl + HClO 3 (when heated)

Esep3.

Sizderde calcium carbonate y zhane tuz kyshkyly bar. Wasps zattar arkyly 6-dan by whom emes zhana zattardy, onyn ishinde 2 zhai zattardy kalay aluga bolady? Synthesis tek kana bastapky zattardy, olardan alyngan onnіmderdi koldanuga bolady, catalyst zhane electr togy kazhet.

Sheshui.

1. CaCO 3 \u003d CaO + CO 2 (kyzdyrganda)

2. CaCO3 + HCl = CaCl2 + CO2 + H2O

3. CaCO3 + CO2 + H2O = Ca(HCO3)2

4. CaO + H2O = Ca(OH)2

5. CaCl 2 \u003d Ca + Cl 2 (balkyma electrolysis i)

6. 2 HCl \u003d H 2 + Cl 2 (erіtndі electrolysis i)

7. 2 H 2 O \u003d 2 H 2 + O 2 (electrolysis)

8. Ca + H 2 \u003d CaH 2

9. Ca(OH)2 + Cl2 = CaOCl2 + H2O (0ºC-de)

10. 6Ca(OH)2 + 6Cl2 = 5CaCl2 + Ca(ClO3)2 + 6H2O ( kyzdyrgan kezde)

11. Cl2 + H2O = HCl + HClO (0ºC -de)

12. 3Cl2 + 3H2O = 5HCl + HClO3 (kyzdyrgan kezde)

Task 4.

A gas mixture containing two hydrogen halides has a hydrogen density of 38. The volume of this mixture at n. y. was absorbed by an equal volume of water. 11.2 ml of 0.4 mol/l sodium hydroxide solution was used to neutralize 100 ml of the resulting solution.

1. Determine which hydrogen halides could be contained in this mixture.

2. Calculate the composition of the gas mixture in volume percent.

3. Suggest a method for determining the qualitative composition of a gas mixture.

Decision.

1. Mass of 1 mol of a gas mixture at n. y. is 38 2 \u003d 76 g. Thus, in the gas mixture cannot be present simultaneously HBr and HI ( M(HBr) \u003d 81 g / mol, M(HI ) = 128 g/mol). Also, they cannot be present at the same time. HF and HCl ( M(HF) = 20 g/mol, M(HCl ) = 36.5 g/mol). The mixture must contain a hydrogen halide withMless than 76 g/mol and hydrogen halide withMmore than 76 g/mol. Possible mixture compositions: 1) HF and HBr; 2) HF and HI; 3) HCl and HBr; 4) HCl and HI.

The concentration of hydrogen halides in the solution is (11.2 0.4): 100 = 0.0448 mol/l. This value corresponds quite well to the calculated value of 1:22.4 = 0.0446 mol/l for the process of dissolving 1 liter of gas (n.a.) in 1 liter of water (provided that the hydrogen halide molecules are monomeric). Thus, the gas mixture does not contain hydrogen fluoride, which is also in the gas phase in the form ( HF ) n , where n = 2-6.

Then only two variants of mixtures correspond to the conditions of the problem: HCl + HBr or HCl + HI.

2. For a mixture of HCl + HBr: let x mole - quantity HCl in 22.4 liters of the mixture (n.a.). Then the amount HBr is (1-x ) mol. The mass of 22.4 liters of the mixture is:

36.5x + 81(1-x) = 76; x = 0.112; 1-x=0.888.

The composition of the mixture: HCl - 11.2%, HBr - 88.8%.

Similarly for a mixture HCl+HI:

36.5x + 128(1-x) = 76; x = 0.562.

Composition of the mixture: HCl - 56.2%, HI - 43.8%

3. Since both mixtures must contain hydrogen chloride, it remains to qualitatively determine hydrogen bromide or hydrogen iodide. This definition is more convenient to make in the form of simple substances - bromine or iodine. To convert hydrogen halides into simple substances, an aqueous solution can be oxidized with chlorine:

2HBr + Cl2 = 2HCl + Br2

2HI + Cl2 = 2HCl + I2

The resulting halogen solutions can be distinguished by the color of the solution in a non-polar solvent (during extraction) or by the more sensitive starch color reaction.

Also, the original hydrogen halides can be distinguished by the different color of the silver halides:

HBr + AgNO 3 = AgBr ↓ + HNO 3 (light yellow precipitate)

HI + AgNO 3 = AgI ↓ + HNO 3 (yellow precipitate)

Esep 4.

Eki halogensutekten turatyn gas kospasynyn sutek boyinsha tygyzdygy 38. Wasps kospanyn қ.zh. Alyngan 100 ml eritindin beitaraptaganda 11.2 ml 0.4 mol/l sodium hydroxydinin eritindisi jumsalda.

1. Osy kospada kandai halogensutek baryn anyktanyzdar.

2. Gas kospasynyn құramyn kolemdіk percentpen anyқtaңyzdar.

3. Gaz kospasynyn sapasyn anyktaytyn zhagdaydy usynynyzdar.

Sheshui.

1. 1 mol gas kospasynyn massasy қ.zh. kuraydy: 38 2 \u003d 76 g. M(HBr) = 81 g/mol, M(HI) = 128 g/mol) bola almaida. Sonymen katar bіr mezgіlde HF jane HCl ( M(HF) = 20 g/mol, M(HCl) = 36.5 g/mol) bola almaida. Kosapada M massasy 76g/moldan az halogensutek bolusy kerek. Mүmkin bolatyn gas cospalary: 1) HF and HBr; 2) HF instead of HI; 3) HCl instead of HBr; 4) HCl instead of HI.

Eritindidegi halosutecterdin concentrations (11.2 0.4): 100 = 0.0448 mol/l. Bulman 1 liter of suғa (halogensutec molecules monomers bulgan zhagdaida) 1 liter of gas (қ.zh.) erіtu process үshіn tөmendegi esepteu nәtizhesіne zhақyn: 1:22.4 = 0.0446 mol/l. Endeshe, gas cospasynda fluorosutek bolmaidy, sebiol gas fazasynda (HF)n turinde bolada, mundagy n = 2-6.

Endeshe eseptin sharty tek ekі nuskaga seykes keledi: HCl + HBr nemese HCl + HI.

2. HCl + HBr kospasy ushіn: 22.4 l kospadagy (қ.zh.) HCl small - x. Onda HBr younger (1-x) bolada mole. 22.4 l kospanyn massasy:

36.5x + 81(1-x) = 76; x = 0.112; 1-x=0.888.

Kospa kuramy: HCl - 11.2%, HBr - 88.8%.

Kospa Ushin HCl+HI:

36.5x + 128(1-x) = 76; x = 0.562.

Kospa kuramy: HCl - 56.2%, HI - 43.8%

3. Endeshe bromsutek zhane iodsutek ekі kospa da boluy seems. Bul anyktama zhai zat turinde - bromine nemese iod anyktauga yngayly. Halogensutekti zhai zatka aynaldyru ushіn onyn erіtіndіsіn chlormen totyқtyru kazhet:

2HBr + Cl2 = 2HCl + Br2

2HI + Cl2 = 2HCl + I2

Halogenderdin alyngan erіtіndіlerіn non-polar erіtkіshtegі erіtіndinіnіn tүsі boyinsha (extarction of kezіndegi) nemese starchdyn аserі аrkyly anyқtauға bolady.

Sondai-aқ halosutekterdi kүmіs halogenidіndegi әrtүrlі tusterі arkyly anқtauғa boladas:

HBr + AgNO3 = AgBr↓ + HNO3 (ashyk-sary tunba)

HI + AgNO3 = AgI↓ + HNO3 (sary tunba)

Problem 5 (Thermochemical calculations, impurities).

When burning 1.5 g of a zinc sample, 5.9 kJ of heat was released. Determine if the zinc sample contained non-combustible impurities if it is known that 348 kJ of heat is released when burning 1 mole of zinc.

Esep5 ( Kospalar, tyermochemiyalyk esepteuler). 1.5 g myrysh үlgisіn zhakanda 5.9 kJ zhylu bolіndі. 1 mole of myryshty zhakanda 348 kJ zhylu bөlіnetinіn bіle otyryp myrysh үlgisіnde zhanbaityn қospalar barma, zhқpa anyқtaңyzdar.

Decision:

Sheshui:

CHEMISTRY

Conclusion

Exercise 1.

Decipher the chain of transformation and carry out chemical reactions:

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Additionally known:

Substance A– corundum

SubstanceB- the most common metal (Me) in the earth's crust

Substance C- a compound containing 15.79% Me, 28.07% S, 56.14% O

Substance E- a white gelatinous substance, poorly soluble in water. The product of the interaction of substance C with alkali

SubstanceD- the sodium salt of the most common metal, the molecule of which contains 40 electrons.

Decision:

A - Al 2 O 3

B-Al

C - Al2(SO4)3

D - NaAlO2

E – Al(OH)3

For each specific formula of the substance - 1 point

For each correct written chemical reaction equation (with implementation conditions) - 2 points

TOTAL: 5 1+8 2 = 21 points

1 tapsirma.

Ainalular tizbegin ashyp, chemistry reaction of tendeulerin zhazynyzdar:

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Kosymsha Belgili Bulgarians:

BUTzaty– corundum

Bzaty– zher sharynda en köp taralgan metal (Me)

With zaty - 15.79% Me, 28.07% S, 56.14% O turatyn kosylys

E zaty - ak koimalzhyn zat, courts of ours eridi. Zattyn siltimen әrekettesuinіnіn өnіmi С

D– en köp taralgan metaldyn sodium aces, molecules 40 electronnan turada.

Sheshui:

A - Al2O3

B-Al

C - Al2(SO4)3

D - NaAlO2

E – Al(OH)3

Әrbіr zattyn formulasyn anyktaғanga - 1 ұpaydan

Durys zhazylgan әrbіr chemiyalyk reaction tendeuine (sharty korsetilgen) – 2 ұpaydan

BARLYGY: 5 1 + 8 2 \u003d 21 upay

Task 2.Six numbered beakers (beakers) contain solids (in the form of powders): sodium bicarbonate, sodium chloride, zinc sulfate, potassium phosphate, calcium carbonate, iron sulfate ( II ). Using the reagents and equipment on the table, determine the contents of each vial (beaker). Lead chemical formula each substance and write the equations of the chemical reactions carried out.

Reagents: 2 M HCl, 2 M NaOH, H 2 O distilled, 2M solution AgNO3

Equipment:rack with test tubes (7-10 pieces), spatula, pipettes.

Decision:

	Stages of work	Observations	Reaction equations, conclusions
	Dissolve samples of substances in water	One substance did not dissolve	This is CaCO3
	Add dissolved and undissolved matter to samples HCl	Gas is released in two test tubes.	NaHCO3 + HCl = CaCO3 + HCl =
	Add sodium hydroxide solution to sample substances (not excess)	In two test tubes precipitates are green (marsh) and white amorphous.	These are FeSO4 and Zn(NO3)2 FeSO4 + NaOH = Zn(NO3)2 + NaOH=
	Add silver nitrate drop by drop to the samples	In two test tubes, white curdled and yellow precipitates fall out.	These are NaCl and K3PO4 NaCl + AgNO3 = K3PO4 + AgNO3=

For the definition of each substance, 1 point.

For the reaction equation - 2 points

Total: 6 1+6 2 = 18 points

Note: If all the coefficients are not placed in the reaction equation, but the essence of the chemical reaction is reflected - 1 point

2 tapsirms.Alty nomerlengen byukste (chemical glass) katty zat bar (ұntak turinde): sodium hydrocarbonates, sodium chloride, myryshg sulfates, potassium phosphates, calcium carbonates, temir (II) sulfates. Stoldagy reaktivterdi zhane kuraldardy paydalana otyryp, arbir byukstegi zatty anyқtaңyzdar. Әrbіr zattyn chemiyalyk formulasyn zhane himiyalyk reaction tendeulerin zhazynyzdar.

Reagent:2M HCl, 2M NaOH, distildengen H2O, 2M AgNO3 eritindis

Құral-zhabdyқtar: probirkalary bar tripod (7-10 dan), spatula (ұstagysh), pipette alar.

Sheshui:

	Zhymys etaptary	Kubylys	Tendeuleri reaction
	Zattyn son of the masons of the court of eritu	Bir zat ta erigen zhok	Bull CaCO3
	Yerigen zhane erimegen zattyn son of a masyn NSI kosu	Eki test tube gas bөlinedі	NaHCO3 + HCl = CaCO3 + HCl =
	Zattyn of the son of the mother's son sodium hydroxydin kosu (az molsherde)	Ekі prrobirkada zhasyl tusti (saz balshyқ tәrіzdі) zhane ak tusti amorty tunba payda bolada	Bull FeSO4 and Zn(NO3)2 FeSO4 + NaOH = Zn(NO3)2 + NaOH=
	Synamaga tamshylatyp kүmis nitratyn қosamyz	Ekі test tube ақ іrіmshіk tәrіzdі zhane sary tұnba tүsedі.	Bul NaCl zhane K3PO4 NaCl + AgNO3 = K3PO4 + AgNO3=

Arbir zatty anyktaganga 1 ұpaydan.

Arbir tendeuine reaction - 2 ұpaydan.

Barlygy: 6 1+6 2 = 18Upay

Eskertu: Yeger tendeuinde barlyk reaction coefficient koyylmagan bolsa, biraq chemiyialik reaction mani anyқtalgan bolsa – 1 ұpay beruge bolada

If a dry gas outlet tube is required for the experiment, then proceed as follows. A rubber tube with a glass tip is put on the free end of the gas outlet tube. When testing the tightness of the device, the removable tip will get wet, and the gas outlet tube will remain dry.

Gas can be collected in a container in a variety of ways. The two most common are the air displacement method and the water displacement method. Each of them has its own advantages and disadvantages, and the choice of method is largely determined by the properties of the gas to be collected.

Air displacement method

Any gas can be collected by this method, but here the problem arises of accurately determining the moment when all the air from the receiver vessel will be displaced by the collected gas.

Before collecting gas by displacement of air, it is necessary to find out whether it is heavier or lighter than air. The position of the receiving vessel will depend on this (Fig.). To do this, calculate the relative density of the gas in air according to the formula: D air. (X) = Mr(X)/29, where Mr is the relative molecular weight of the collected gas, 29 is the relative molecular weight of the air. If the calculated value turns out to be less than one, then the gas is lighter than air, and the receiving vessel must be placed with the hole down (Fig. 57, a). If the relative density of the gas in air is greater than one, then the gas is heavier than air, and the receiving vessel should be positioned with the hole up (Fig. 57,b).

Rice. 57. The position of the receiver vessel (1): a - for a gas that is lighter than air; b - for a gas that is heavier than air.

The filling of the vessel can be controlled in different ways depending on which gas is being collected. For example, colored nitric oxide (IV) is easily detected by its red-brown color. To detect oxygen, a smoldering splinter is used, which is brought to the edge of the vessel, but not brought inside.

Water displacement method.

When using this method, it is much easier to control the filling of the receiving vessel with gas. However, this method has a serious limitation - it cannot be used if the gas dissolves in water or reacts with it .

To collect gas by displacement of water, it is necessary to have a wide vessel, for example, a crystallizer, filled 2/3 with water. The receiving vessel, such as a test tube, is filled to the top with water, closed with a finger, quickly turned upside down and lowered into the crystallizer. When the opening of the test tube is under water, the opening of the test tube is opened and a gas outlet tube is inserted into the test tube (Fig. 58).

Rice. 58. Device for collecting gas by the method of water displacement: 1 - receiver tube filled with water; 2 - crystallizer.

After all the water has been displaced from the tube by the gas, the opening of the test tube closed under water stopper and removed from the crystallizer.

If the gas, which is collected by the displacement of water, is obtained by heating, the following rule must be strictly observed:

Do not stop heating the test tube with starting substances if the gas outlet tube is under water!

Registration of the results of the experiment

The form of recording the results obtained during the performance of a chemical experiment is not regulated by anyone. But the protocol of the experiment must necessarily include the following items: the name of the experiment and the date it was carried out, the purpose of the experiment, the list of equipment and reagents that were used, the drawing or diagram of the device, a description of the actions that were performed during the work, observations, equations of ongoing reactions, calculations , if they were made during the performance of the work, conclusions.

Form of the report on the carried out practical work.

Write down the date of the experiment and the name of the experiment.

State the purpose of the experiment.

Briefly write down everything you did.

Make a drawing of the experiment or draw the device you used. Try to keep the drawing clear. Be sure to add explanatory notes to the picture. For the image of colored substances, use colored pencils or felt-tip pens.

Write down your observations, i.e. describe the conditions for the occurrence and signs of chemical reactions.

Write equations for all the chemical reactions that took place during the experiment. Don't forget to set the odds.

Draw a conclusion from experience (or work).

You can draw up a report on the work as a sequential description of actions and observations, or in the form of a table:

Experience no...

Experience Description	Drawing experience	Signs of reactions	Findings. Reaction equations

When solving experimental problems related to the recognition and identification of substances, it is convenient to format the report in the form of another table:

Procedure	Reagent	Tube number			Conclusion

Topic 1. Basic concepts and laws of chemistry.

Laboratory experiments.

Examples of physical phenomena.

Experience No. 1. Heating glass (glass tube)

in the flame of an alcohol lamp.

Equipment and reagents: glass tube, spirit lamp, matches, asbestos mesh.

1. Hold the glass tube by its ends with both hands.

2. Bring the middle part of the tube into the flame of the spirit lamp. Remember that the top of the flame is the hottest.

3. Rotate the tube without taking it out of the flame of the spirit lamp (Fig. 59).

4. When the glass becomes very hot (after 3-4 minutes), try to bend the tube without applying excessive force.

Rice. 59. Bending a glass tube.

Lay the glass tube on the asbestos mesh. Be careful: hot glass appearance no different from cold!

1) Has the glass changed?

2) Was a new substance obtained by heating the glass tube?

Experience No. 2. Melting of paraffin.

Equipment and reagents: crucible or glass plate, spirit lamp, matches, crucible tongs or test tube holder, asbestos mesh, paraffin.

Instructions for performing the experiment.

1. Put a small piece of paraffin into the crucible (or onto a glass plate).

2. Take the crucible (or glass plate) with crucible tongs (or fix it in a test tube holder).

3. Insert the wax crucible (or glass plate) into the top of the spirit lamp flame. Watch the changes carefully.

4. After melting the paraffin, place the crucible (or glass plate) on the asbestos mesh and turn off the spirit lamp.

5. When the crucible (or glass plate) has cooled, examine the substance that is in the crucible (or glass plate).

1) Has the paraffin changed?

2) Was a new substance obtained by heating paraffin?

3) What is this phenomenon: physical or chemical?

Examples of chemical phenomena.

Experience No. 3. Ignition of a copper plate or wire

in the flame of an alcohol lamp.

Equipment and reagents: spirit lamp, matches, crucible tongs or test tube holder, asbestos mesh, copper wire or plate.

Instructions for performing the experiment.

1. Take a copper plate (or copper wire) with crucible tongs.

2. Insert a copper plate into the top of the spirit lamp flame and heat it up.

3. After 1-2 minutes, remove the plate from the flame and clean off the formed black coating from it with a knife or a splinter on a clean sheet of paper.

4. Repeat the heating and again clean off the resulting plaque.

5. Compare the resulting black coating with a copper plate.

1) Has the copper plate changed when heated?

2) Was a new substance formed when the copper plate was heated?

3) What is this phenomenon: physical or chemical?

Experience number 4. Action of hydrochloric acid on chalk or marble.

Equipment and reagents: chemical beaker with a volume of 50 ml, marble (small pieces or crumbs), hydrochloric acid solution (1: 3), matches.

Instructions for performing the experiment.

1. In a beaker, place 2-3 small pieces of marble the size of a pea. Be careful not to break the bottom of the glass.

2. Pour enough hydrochloric acid into a glass so that the pieces of marble are completely covered with it. What are you watching?

3. Light a match and put it into the cup. What are you watching?

4. Draw the experiment, write down your observations.

1) Was a new substance formed when hydrochloric acid was added to marble? What is this substance?

2) Why did the match go out?

3) What is this phenomenon: physical or chemical?

Types of chemical reactions.

Gaseous substances from the course of inorganic and organic chemistry

In preparation for the upcoming exams, graduates of the 9th and 11th grades need to study the issue of gaseous substances ( physical properties ah, methods and methods of obtaining, their recognition and application). Exploring specification topics OGE exams and Unified State Examination (on the websitewww. fipi. en ), we can say that there is practically no separate issue on gaseous substances (see table):

USE

№14 (Characteristic chemical properties of hydrocarbons: alkanes, cycloalkanes, alkenes, dienes, alkynes, aromatic hydrocarbons (benzene and toluene). Main methods for obtaining hydrocarbons (in the laboratory);№26 (Rules for working in the laboratory. Laboratory glassware and equipment. Safety rules when working with caustic, combustible and toxic substances, household chemicals. scientific methods research chemical substances and transformations. Methods for separation of mixtures and purification of substances. The concept of metallurgy: general methods for producing metals. General scientific principles chemical production(on the example of industrial production of ammonia, sulfuric acid, methanol). chemical pollution environment and its consequences. Natural sources of hydrocarbons, their processing. Macromolecular compounds. Reactions of polymerization and polycondensation. Polymers. plastics, fibers, rubbers)

So, in option No. 3 (Chemistry. Preparation for the OGE-2017. 30 training materials based on the 2017 demo. Grade 9: teaching aid / ed. V.N. Doronkin. - Rostov n / D: Legion, 2016. - 288 p.), students were asked to answer the following question (No. 13):

Are the following judgments about the methods of obtaining substances correct?

A. Ammonia cannot be collected by displacing water.

B. Oxygen cannot be collected by displacing water.

1) only A is true

2) only B is true

3) both statements are correct

4) both judgments are wrong

To answer the question, the guys should know the physical and chemical properties of ammonia and oxygen. Ammonia interacts very well with water, therefore, it cannot be obtained by the method of water displacement. Oxygen dissolves in water, but does not interact with it. Therefore, it can be obtained by the method of water displacement.

In option No. 4 (Chemistry. Preparation for the Unified State Examination-2017. 30 training options according to the demo version for 2017: teaching aid / ed. V.N. Doronkin. - Rostov n / D: Legion, 2016. - 544 p.), students were asked to answer the following question (No. 14):

From the proposed list, select two substances that are formed when a mixture of solid potassium acetate and potassium hydroxide is heated:

1) hydrogen;

2) methane;

3) ethane;

4) carbon dioxide;

5) potassium carbonate

Answer: 2 (decarboxylation reaction)

Moreover, for passing the exam children need to know what is the raw material for obtaining one or another gaseous substance. For example, in the same book, edited by Doronkin, question No. 26 (option 8) sounds like this:

Establish a correspondence between the substance obtained in industry and the raw material used to obtain it: for each position indicated by a letter, select the corresponding position indicated by a number:

Write in the table the selected numbers under the corresponding letters:

Answer:

In option No. 12, students are asked to recall the scope of some gaseous substances:

Establish a correspondence between the substance and its scope: for each position indicated by a letter, select the corresponding position indicated by a number:

Answer:

With the guys taking the exam in chemistry in the 9th grade, in the preparation for the exam, we fill out the following table (in the 11th grade we repeat it and expand it):

Hydrogen

Most light gas, 14.5 times lighter than air, with air in the ratio of two volumes of hydrogen to one volume of oxygen forms "explosive gas"

1. Through the interaction of alkaline and alkaline earth metals with water:

2 Na + 2 H 2 O = 2 NaOH + H 2

2. Interaction of metals (up to hydrogen) with hydrochloric acid (any concentration) and dilute sulfuric acid:

Zn + 2 HCl = ZnCl 2 + H 2

3. Interaction of transition (amphoteric) metals with a concentrated alkali solution when heated:

2Al + 2NaOH ( conc ) + 6H 2 O = 2Na + 3H 2

4. Decomposition of water under the influence of electric current:

2H 2 O=2H 2 +O 2

According to the characteristic sound of the explosion: a vessel with hydrogen is brought to the flame (deaf clap - pure hydrogen, "barking" sound - hydrogen mixed with air):

2H 2 +O 2 2H 2 O

Hydrogen burner, margarine production, rocket fuel, production of various substances (ammonia, metals such as tungsten, hydrochloric acid, organic matter)

Oxygen

Colorless gas, odorless; in the liquid state it has a light blue color, in the solid state it is blue; more soluble in water than nitrogen and hydrogen

1. By decomposition of potassium permanganate:

2 KMnO 4 = K 2 MNO 4 + MNO 2 + O 2

2. By decomposition of hydrogen peroxide:

2 H 2 O 2 2 H 2 + O 2

3. Decomposition of Bertolet salt (potassium chlorate):

2KClO 3 = 2KCl + 3O 2

4. Decomposition of nitrates

5. Decomposition of water under the influence of electric current:

2 H 2 O = 2 H 2 + O 2

6. Photosynthesis process:

6 CO 2 + 6 H 2 O = C 6 H 12 O 6 + 6O 2

The flash of a smoldering splinter in a container of oxygen

In metallurgy, as an oxidizer for rocket fuel, in aviation for breathing, in medicine for breathing, in blasting, for gas cutting and welding of metals

Carbon dioxide

Colorless gas, odorless, 1.5 times heavier than air. Under normal conditions, one volume of water dissolves one volume carbon dioxide. At a pressure of 60 atm, it turns into a colorless liquid. When liquid carbon dioxide evaporates, part of it turns into a solid snow-like mass, which is pressed in industry - “dry ice” is obtained.

1. Limestone calcination industry:

CaCO 3 CaO + CO 2

2. The action of hydrochloric acid on chalk or marble:

CaCO 3 + 2HCl = CaCl 2 + H 2 O+CO 2

With the help of a burning splinter that goes out in an atmosphere of carbon dioxide, or by clouding lime water:

CO 2 + Ca(Oh) 2 = CaCO 3 ↓ + H 2 O

For creating "smoke" on stage, storing ice cream, in fizzy drinks, in foam fire extinguishers

Ammonia

A colorless gas with a pungent odor, almost 2 times lighter than air. You can not inhale for a long time, because. he is poisonous. Easily liquefies at normal pressure and temperature -33.4 about C. When liquid ammonia evaporates from the environment, a lot of heat is absorbed, so ammonia is used in refrigeration. Highly soluble in water: at 20 about C About 710 volumes of ammonia dissolve in 1 volume of water.

1. In industry: when high temperatures, pressure, and in the presence of a catalyst, nitrogen reacts with hydrogen to form ammonia:

N 2 +3 H 2 2 NH 3 + Q

2. In the laboratory, ammonia is obtained by the action of slaked lime on ammonium salts (most often ammonium chloride):

Ca(OH) 2 + 2NH 4 Cl CaCl 2 + 2NH 3 + 2H 2 O

1) by smell;

2) by changing the color of wet phenolphthalein paper (turned crimson);

3) by the appearance of smoke when bringing a glass rod moistened with hydrochloric acid

1) in refrigeration units; 2) production mineral fertilizers;

3) production nitric acid;

4) for soldering; 5) receiving explosives; 6) in medicine and in everyday life (ammonia)

Ethylene

Under normal conditions - colorless gas with a slight odor, partially soluble in water and ethanol. Let's well dissolve in diethyl ether and hydrocarbons. It is a phytohormone. Has narcotic properties. The most produced organic matter in the world.

1) In the ethane dehydrogenation industry:

CH 3 -CH 3 CH 2 =CH 2 + H 2

2) Ethylene is produced in the laboratory in two ways:

a) depolymerization of polyethylene:

(-CH 2 -CH 2 -) n nCH 2 =CH 2

b) catalytic dehydration of ethyl alcohol (white clay or pure alumina and concentrated sulfuric acid):

C 2 H 5 OHCH 2 =CH 2 + H 2 O

Oxygen

+

upside down

+

Upside down

Carbon dioxide

+

upside down

-

Ammonia

+

Upside down

-

Ethylene

+

Upside down and slanted

-

So for successful delivery OGE and USE, students need to know the ways and methods of obtaining gaseous substances. The most common of these are oxygen, hydrogen, carbon dioxide and ammonia. In the 11th grade textbook, children are offered practical work No. 1, which is called "Receiving, collecting and recognizing gases." It proposed five options - obtaining five different gaseous substances: hydrogen, oxygen, carbon dioxide, ammonia and ethylene. Of course, in a lesson lasting 45 minutes, all 5 options are simply unrealistic to complete. Therefore, before starting this work, students at home fill out the above table. Thus, the guys at home, when filling out the table, repeat the methods and methods for obtaining gaseous substances (chemistry course of grades 8, 9 and 10) and come to the lesson already theoretically aware. For one topic, graduates receive two grades. The work is big, but the guys are happy to do it. And the incentive is - a good mark in the certificate.

Analysis of the distribution of physical forces
when using chemicals

The demonstration experiment and many practical works are based on the use of simple chemical devices. In addition to getting acquainted with the chemical transformations of substances, students must understand physical entity what is happening, and be able to explain the essence of what is happening according to the drawing of the device: what is moving where and what is happening where.

One of the instruments in the chemistry lab is a gasometer. On fig. 1 shows a gasometer filled with gas. It can be oxygen, as indicated in the figure, carbon dioxide, or simply air. Cranes 1 and 2 closed at this moment. Gas in accordance with Pascal's law exerts pressure on the walls of the vessel and water. Opening the faucet 1 , the column of water from the funnel puts pressure on the gas, squeezing it, but since internal gas pressure and water pressure are balanced, nothing happens. Opening the faucet 2 , the gas rushes into the outlet (the flow rate is adjusted by carefully turning the cock). The pressure inside the vessel drops - and water from the funnel enters the gasometer. After the faucet is closed 2 gas extraction is stopped, the water level is set at a higher level, because. there is a new balance of power. Turn off the tap to stop the water pressure 1 .

The second device, similar to a gasometer, is the Kipp apparatus (Fig. 2). This device can produce hydrogen from zinc and hydrochloric acid (see Fig. 2), hydrogen sulfide from iron sulfide, carbon dioxide from marble. In position a the device is in working condition, the tap is open. A strong solution of hydrochloric acid rushes into the lower part of the device, fills it and wets the zinc metal lying on the copper grid. Zinc dissolves in acid, reacts with it, the resulting hydrogen rushes into the middle sphere of the device, displaces air, mixing with it. Therefore, the outgoing gas must be checked for purity. The distribution of physical forces in the device is shown in fig. 2 with arrows.

We close the tap. Hydrogen continues to form, its quantity increases. Since the gas outlet is blocked, the pressure inside the sphere increases. It squeezes the acid out of the middle sphere until the acid no longer covers the surface of the zinc. Chemical reaction stops (zinc wetted with acid continues to react with it for some time). The internal pressure in the device, created by hydrogen, and the pressure created by the hydraulic seal, are balanced.

Consider the methods of collecting gases. On fig. 3 shows how to collect gas by the air displacement method. If the gas is toxic, this operation is carried out in a fume hood. Gases that are heavier than air - CO 2, O 2, HCl, SO 2, entering the jar or beaker, displace the air.

In the study of carbon dioxide: its physical properties and inability to support the combustion of organic substances - is demonstrated entertaining experience extinguishing a paraffin candle burning in air (Fig. 4). Carbon dioxide, being heavier, sinks down under the force of gravity. It fills the container and displaces the air it contains. A candle in an atmosphere of carbon dioxide goes out.

The device shown in fig. 5, students collect on practical work"Production of oxygen and the study of its properties". This instrument illustrates the method of collecting gas by displacing air (a physical justification for the concept of "relative density").

Another way of collecting gases is associated with the displacement of water from the vessel. In this way, it is possible to collect gases that are slightly soluble in water, in particular, nitric oxide (II) (Fig. 6). Gas from the reactor 1 enters the gas pipe 2 placed under an upside down cylinder 3 . Passing through the water column, the gas is collected in the area of ​​the bottom of the cylinder. The pressure of the gas pushes the water out of the cylinder.

If a gas is poorly soluble in water, then this gas can

but to saturate the water, as shown in fig. 7. In such a device, chlorine (see Fig. 7) or sulfur dioxide can be obtained by adding concentrated sulfuric acid to sodium sulfite crystals. The gas obtained in the Wurtz flask enters the gas outlet tube, which is immersed in water at the end. Partially, the gas dissolves in water, partially fills the space above the water, displacing air.

If the gas is highly soluble in water, then it cannot be collected by the water displacement method. On fig. Figures 8 and 9 show how hydrogen chloride and ammonia are collected by the air displacement method. On the same Fig. 8 and 9
(see c. 22) shows the dissolution of gases when test tubes with HCl and NH 3 are immersed in water with a hole.

If you saturate with hydrogen chloride from a test tube (with reagents) with a gas outlet pipe lowered into water (Fig. 10), then the first portions of the gas instantly dissolve in water. About 500 liters of hydrogen chloride are dissolved in 1 liter of water, therefore, the incoming gas does not create excess pressure. On fig. 10 marked sequential change in gas pressure p ext in the reaction tube with respect to atmospheric pressure p atm. The pressure inside the device becomes less than the external pressure, and water rapidly fills the gas outlet tube and the device itself. In addition to the fact that the experiment is ruined, the test tube can also crack.

When studying the chemical properties of metallic sodium (Fig. 11), it is important not only to observe its behavior in the reaction with water, but also to explain the observed phenomena. The first observation is that sodium remains on the surface of the water, therefore, its density is less than unity (the density of water). The second observation is that sodium "rushes" through the water due to the repulsive effect of the released gas. The third observation is that sodium melts and turns into a ball. The reaction of interaction of sodium with water is exothermic. The heat released is enough to melt sodium, therefore, it is a fusible metal. The fourth observation is that the reaction is accompanied by flashes, therefore, the heat of reaction is sufficient for spontaneous combustion of sodium and for a microexplosion of hydrogen. If the reaction is carried out in a narrow space (in a test tube), and even with a large piece of sodium, then a hydrogen explosion cannot be avoided. To avoid an explosion, the reaction is carried out in a crystallizer or in a beaker with a large diameter and using a small piece of sodium.

It is necessary to pay great attention to the rule of dissolving concentrated sulfuric acid in water (Fig. 12). The acid, as a heavier liquid, rushes to the bottom of the round bottom flask. Everything else is shown in Fig. 12.

The formation of physical and chemical thinking is facilitated by the study of oxygen (as in primary course chemistry, as well as in the course of organic chemistry). It's about on the use of oxygen and acetylene in welding and autogenous metal cutting (Fig. 13). When welding, the high-temperature flame of acetylene burning in oxygen (up to 2500 ° C) is directed to the metal wire and the place to be welded. The metal melts, a seam is obtained. In autogenous cutting, the flame melts the metal, and excess oxygen burns it out.

Not every chemistry lab has silicon as simple matter. Let's check it for electrical conductivity using the simplest device: a probe with elastic elongated iron ends, a light bulb (mounted on a stand), and an electrical wire with a plug (Fig. 14). The light bulb glows, but not brightly - it is clear that silicon conducts electric current, but provides significant resistance to it.

Chemical element Silicon is an analogue of carbon, but the radius of its atoms is greater than the radius of carbon atoms. Silicon, as a simple substance, has the same (like diamond) crystal lattice (atomic) with a tetrahedral orientation chemical bonds. In diamond covalent bonds durable, it does not conduct electricity. In silicon, as even a rough experiment shows, some of the electron pairs are depaired, which causes some electrical conductivity of the substance. In addition, silicon is heated (some students have the opportunity to verify this), which also indicates the resistance of the substance to electric current.

With great interest, students observe the study of the physical and chemical properties of benzene (Fig. 15). Add a layer of benzene ~2 mm thick to a small amount of water (see Fig. 15, a). It can be seen that the two colorless liquids do not mix. We mix this stratified mixture with intensive shaking, we get a "gray" emulsion. Fix the test tube in a vertical position. Students observe the gradual stratification of benzene and water, and at first the lower level of the content becomes transparent, and after a short time we get the initial distribution. Water molecules are lighter than benzene molecules, but its density is slightly higher. The interaction between non-polar benzene molecules and polar water molecules is negligible, very weak, so most of the benzene is pushed to the surface of the water (see Fig. 15, b).

Now add benzene to a few milliliters bromine water(small staining intensity) (see Fig. 15, b). Liquids do not mix. Intensively mix the contents of the test tube and allow the system to settle. Bromine, previously dissolved in water, is extracted into the benzene layer, as can be seen from the change in color and increase in its intensity.

Add a few milliliters of a weak alkali solution to the contents of the test tube
(see fig. 15, b). Bromine reacts with alkali. The benzene layer becomes colorless, and the resulting inorganic substances and water passes into the lower (water) layer.

In this article, we limited ourselves to examples that illustrate not only the connection between teaching chemistry and physics, but compensate for the lack of textbooks in which the named physical phenomena, as a rule, are not reflected.

Kipp apparatus used to produce hydrogen, carbon dioxide and hydrogen sulfide. The solid reagent is placed in the middle spherical reservoir of the apparatus on a plastic annular insert, which prevents the solid reagent from entering the lower reservoir. Zinc granules are used as a solid reagent for producing hydrogen, pieces of marble are used for carbon dioxide, and pieces of iron sulfide are used for hydrogen sulfide. The solids to be poured should be about 1 cm 3 in size. It is not recommended to use powder, as the gas current will turn out to be very strong. After loading the solid reagent into the apparatus, a liquid reagent is poured through the upper neck (for example, a dilute solution of hydrochloric acid in the production of hydrogen, carbon dioxide and hydrogen sulfide). The liquid is poured in such an amount that its level (with the gas outlet valve open) reaches half of the upper spherical expansion of the lower part. The gas is passed through for 5-10 minutes to force the air out of the apparatus, then the gas outlet valve is closed, a safety funnel is inserted into the upper throat. The gas outlet tube is connected to the device where the gas must be passed.

When the tap is closed, the released gas displaces the liquid from the spherical expansion of the apparatus, and it stops working. When the tap is opened, the acid again enters the tank with a solid reagent, and the apparatus starts to work. This is one of the most convenient and safe methods for obtaining gases in the laboratory.

Collect gas in a vessel can various methods. The two most common methods are the water displacement method and the air displacement method. The choice of method is dictated by the properties of the gas to be collected.

Air displacement method. Almost any gas can be collected by this method. Before taking a gas, it is necessary to determine whether it is lighter than air or heavier. If the relative density of the gas in air is greater than one, then the receiving vessel should be kept with the hole up, since the gas is heavier than air and will sink to the bottom of the vessel (for example, carbon dioxide, hydrogen sulfide, oxygen, chlorine, etc.). If the relative density of the gas in air is less than unity, then the receiving vessel should be kept with the hole down, since the gas is lighter than air and will rise up the vessel (for example, hydrogen, etc.). The filling of the vessel can be controlled in different ways, depending on the properties of the gas. For example, to determine oxygen, a smoldering torch is used, which, when brought to the edge of the vessel (but not inside!) Flashes; when determining carbon dioxide, the hot torch goes out.

Water displacement method. This method can only collect gases that do not dissolve in water (or slightly dissolve) and do not react with it. To collect gas, a crystallizer is needed, 1/3 filled with water. The receiver vessel (most often a test tube) is filled to the top with water, closed with a finger and lowered into the crystallizer. When the opening of the vessel is under water, it is opened and a gas outlet tube is inserted into the vessel. After all the water is displaced from the vessel by gas, the hole is closed under water with a cork and the vessel is removed from the crystallizer.

Checking the gas for purity. Many gases burn in air. If you set fire to a mixture of combustible gas with air, an explosion will occur, so the gas must be checked for purity. The test consists in burning a small portion of gas (about 15 ml) in a test tube. To do this, the gas is collected in a test tube and set on fire from the flame of an alcohol lamp. If the gas does not contain air impurities, then combustion is accompanied by a slight pop. If a sharp barking sound is heard, then the gas is contaminated with air and needs to be cleaned.