Frank Solutions for Chapter 8 Study of Compounds Hydrogen Chloride Class 10 Chemistry ICSE
1. Name the following:
(i) Acid present in the stomach of mammals.
(ii) Drying agent used to dry hydrogen chloride.
(iii) Salt obtained by heating sodium chloride with concentrated sulphuric add below 200 degree celcius.
(iv) Gas that yields white precipitates dense white fumes when mixed with hydrogen chloride.
(v) Two solutions that yields white precipitates, when treated with hydrogen chloride or hydrochloric acid.
(vi) Gas obtained by treating metals with hydrochloric acid.
(vii) Gas obtained by treating ferrous sulphide with hydrochloric add.
(viii) Five oxidizing agents that liberated chlorine from concentrated hydrochloric acid.
(ix) Acid used to extract glue from bones.
(x) A chloride which is soluble in excess of ammonium hydroxide.
(xi) A greenish yellow gas.
(xii) A chemical in which gold can be dissolved.
(xiii) A metallic oxide which reacts with hydrochloric acid to give a coloured solution.
(xiv) Two colourless gases which when mixed produce a white solid.
Answer
(i) Acid present in the stomach of mammals is hydrochloric acid.
(ii) Concentrated sulphuric acid is used to dry hydrogen chloride gas.
(iii) Salt obtained by heating sodium chloride with concentrated sulphuric acid below 200 degree Celsius is sodium hydrogen sulphate
(iv) When ammonia gas is bubbled through hydrogen chloride white precipitate of ammonium chloride is obtained.
(v) Two solutions that yields white precipitates, when treated with hydrogen chloride or hydrochloric acid are -
- Silver nitrate
- Lead nitrate
(vii) Gas obtained by treating ferrous sulphide with hydrochloric acid is hydrogen sulphide(H2S).
(viii) Five oxidizing agents that liberated chlorine from concentrated hydrochloric acid are -
- MnO2
- PbO2
- KmnO4
- K2Cr2O7
- CaOCl2
(x) Silver chloride is soluble in excess of ammonium hydroxide.
(xi) Chlorine is a greenish yellow gas.
(xii) Gold can be dissolved in aqua regia which is mixture of three parts of concentrated hydrochloric acid and one part of concentrated nitric acid.
(xiii) K2Cr2O7 reacts with hydrochloric acid to give a coloured solution.
(xiv) HCl and NH3 are two colourless gases which when mixed produce a white solid.
2. Calcium oxide and phosphorous pentoxide are very good drying agents but they are not used to dry HCl gas. Give reasons for each.
Answer
Calcium oxide and phosphorous pentoxide are very good drying agents but they are not used to dry HCl gas because they react with hydrogen chloride. 
3. (i) Draw a labelled diagram and explain the laboratory preparation of hydrogen chloride gas.
(ii) How will you prove that the gas prepared is HCI?
(iii) Name the drying agent used to dry HCI gas.
(iv) How is the gas collected and why?
(v) What are the important precautions?
Answer
(i) Hydrogen chloride gas is prepared by the reaction of sodium chloride and sulphuric add at the temperature below 200°C. Sodium chloride is preferred for laboratory preparation of HCI gas since it is cheapest and most easily available chloride. Lower temperature is proffered because at higher temperature sodium sulphate forms a hard crust and sticks to the bottom of the flask and is difficult to remove. 
(ii) A glass rod dipped in ammonia solution is brought near the mouth of the gas jar. Dense white fumes of ammonium chloride will be produced. It proves the presence of Ha gas in the gas jar.
(iii) Concentrated H2SO4 is used to dry HO gas.
(iv) The gas is collected by upward displacement of air because:
- It is heavier than air.
- It is highly soluble in water.
- The lower end of thistle funnel must be dipped below the concentrated H2SO4
- Temperature should be maintained nearly 200°C because at higher temperature:
(a)The apparatus may break
(b)Fuel is wasted.
(c) Sodium sulphate fumed in the reaction forms a crust on the surface which is difficult to remove.
4. How will you prepare hydrochloric acid in laboratory ?
OR
Describe briefly the method employed to dissolve hydrogen chloride gas in water as it is prepared. What is the purpose of funnel while preparing hydrochloric acid from HCl gas ?
Answer
Hydrochloric acid cannot be prepared by mixing hydrochloride gas directly in water as it leads to back suctions.
A complete set up of apparatus for the preparation of hydrochloric acid in laboratory is shown in the given figure. 
Hydrogen chloride gas prepared by the reaction of sodium chloride and sulphuric acid, is passed to inverted funnel arrangement through empty flask. An inverted funnel connected to the HCl gas supply is placed in a beaker in such a way that the rim of the funnel just touches the surface of water in the beaker. HCI gas coming through delivery tube fills the mouth of the funnel and then dissolves in water. By this way we get hydrochloric add in the beaker.
OR
Hydrogen chloride gas is dissolved in water by inverted funnel arrangement. MCI gas cannot be dissolved in water directly as it lead to back suction.
The purpose of funnel while preparing hydrochloric acid from HO gas is :
- To prevent back suction of water.
- It provides a larger surface for dissolution of hydrogen chloride gas.
5. Explain, why (or give reasons for)
(i) In the preparation chloride from sodium chloride, the gas can be obtained below 200°C or above. But the lower temperature is preferred.
(ii) Hydrogen chloride is not collected over water.
(iii) Hydrochloric acid cannot be concentrated above 22.2% by boiling.
(iv) HCI gas does not conduct electricity, but hydrochloric acid conducts electricity.
(v) Only a very dilute solution of hydrogen chloride in water can be concentrated by boiling the solution while a very concentrated solution would become less concentrated when boiled.
(vi) When the stopper of a bottle full of HCI gas is opened there are fumes in the air.
(vii) A solution of HCI gas in water turns blue litmus red and conducts electricity, while HCI gas dissolves in toluene and it has no effect on litmus and does not conduct electricity.
(viii) An aqueous solution of chlorine is acidic is nature.
Answer
(i) Lower temperature is preferred because at higher temperature sodium sulphate forms a hard crust and sticks to the bottom of the flask and is difficult to remove.
(ii) Hydrogen chloride is not collected over water because it is highly soluble in water (iii) Hydrochloric add cannot be concentrated over 22.2% by boiling because this mixture(77.8 % water +22.2 % HCI) bills at a constant temperature of 110°C without any change in concentration. Such a mixture is called as azeotrope
(iv) HCI gas does not conduct electricity ,but hydrochloric add conducts electricity because in hydrochloric add(aq), hydrogen ions are present to facilitate the movement of electrons whereas no such medium is present in gas
(v) Dilute hydrochloric add cannot be concentrated beyond 22.2% (by weight) by distillation: This is due to the fact that this mixture(77.8°Io water +22. 2°/0 HCI) boils at a constant temperature of 1 10°C without any change in concentration. So if its concentration is high it will fall back at a lower concentration
(vi) When the stopper of a bode full of HCI gas is opened there are fumes in the air due to high solubility of HCI gas in water. It fumes in moist air forming a cloud of tiny droplets of hydrochloric acid.
(vii) A solution of HCI gas in water turns blue litmus red and conducts electricity, while HCI gas dissolves in toluene and it has no effect because hydrochloric add is a polar covalent compound In polar solvent like water it ionizes to give hydrogen ions and also facilitates the movement of electrons to conduct electricity while it does not ionize in organic solvents like toluene.
(viii) Dissolved chlorine reacts slowly with water to give hydrochloric acid and hypochlorous acid :
Cl2 + H2O ⟶ HCl + HClO
(ix) Formation of Hydrochloric acid in the reaction is responsible for the acidic nature.
6. what would happen if
(i) Calcium oxide is used to dry hydrogen chloride.
(ii) Concentrated hydrochloric acid is kept open.
(iii) Hydrogen chloride prepared in laboratory, is passed through water, using a delivery tube.
Answer
(i) If calcium oxide is used to dry HO, then it will react with HO gas and result in the formation of calcium chloride and water.
CaO + 2HCl ⟶ CaCl2 +H20
(ii) When concentrated hydrochloric add is kept open, it fumes in moist air forming a cloud of tiny droplets of hydrochloric add.
(iii) Hydrochloric acid is formed when Hydrogen chloride gas prepared in laboratory, is passed through water, using a delivery tube.
7. Write three equations to show that hydrochloric acid acts as an acid.
Answer
In the following reaction, hydrochloric acid acts as an acid.
Zn + 2HCl ⟶ ZnCl2 + H2
CuO + 2HCl ⟶ CuCl2 + H2O
FeS + 2HCl ⟶ FeCl2 + H2S
8. Describe an experiment to prove the following :
(i) HCl gas is heavier than air.
(ii) HCl is highly soluble is water.
(iii) HCl gas contains the element chlorine.
Answer
(i) Two gas jars A and B are taken. A is filled with air and B with dry HCI gas. B is inverted over A , kept for few minutes and then jar is removed. Now a rod dipped in ammonium hydroxide is introduced into the jar A, white fumes are seen. This shows that HCI displaces the air since it is heavier than air. 
(ii) The high solubility of HCI gas can be demonstrated by "Fountain experiment". In it, a well dried round bottom flask is filled with dry HCI gas and fitted with a two holed rubber stopper. A jet tube is inserted into the flask through one of the holes. A dropper filled with water is fitted into the other hole. Closing the outer end of the jet tube, the flask is inverted and the tube is dipped into a blue litmus solution taken in a beaker, then dropper is pressed. It is seen that the blue litmus solution enters the jet tube with a great force, forming a red fountain. 
It happens because water introduced from dropper completely absorbs HCl gas, thereby creating a very low pressure within the flask. To make up for this loss in pressure, blue litmus solution rises in the jet tube and colour of litmus changes to red.
(iii) When HCl gas is heated above 500°C, it dissociates into hydrogen and chlorine. 
9. (a) Name the gas evolved when dilute hydrochloric acid is added to :
(i) Zinc Metal
(ii) Calcium carbonate
(iii) Sodium sulfite
(iv)Lead (II) sulphide
(v) Magnesium bicarbonate
(vi) Potassium bisulphite
(b) Give a balanced equation for each the above reaction.
Answer
(a) (i) Hydrogen
(ii) Carbon dioxide
(iii) Sulphur dioxide
(iv) Hydrogen sulphide
(v) Carbon dioxide
(vi) sulphur dioxide
(b) 
10. (i) What is aqua - regia ?
(ii) State the use of aqua - regia.
(iii) What is the function of HCl in preparation of aqua - regia ?
Answer
(i) Aqua regia is a mixture is 3 parts of concentrated HCI and 1 part of concentrated HNO3 .
(ii) It is used to dissolve noble metals like gold and platinum.
(iii) HCl dissolves noble metals like gold and platinum. HCI with HNO3 reacts to produce nascent chlorine which reacts with gold, platinum etc. to form theft respective chlorides.
11. Give two tests for hydrochloric acid.
Answer
Two tests for hydrochloric acid are -
- When silver nitrate solution is added to hydrochloric acid, it gives white precipitate of silver chloride.
- When lead nitrate solution is added to it, gives white precipitate of lead chloride.
12. Write the uses of hydrochloric acid.
Answer
Uses of hydrochloric acid are:
- It is used in the production of dyes, drugs, paints, photographic chemicals etc.
- It is used in the extraction of bone charcoal, by dissolving away calcium phosphate.
- It is used in the extraction of glue from bones.
- It is used in the production of glucose from starch.
13. Mention the reaction conditions and give balanced equations to obtain
(i) Cl2 gas from HCl gas.
(ii) Cl2 gas from HCl acid.
(iii) HCl gas from common salt
Answer
14. How can you prove that hydrochloric acid contains
(i) Hydrogen,
(ii) Chlorine
Answer
15. Fill in the blanks:
(i) Aqua - regia is a mixture of _____.
(ii) A constant boiling mixture of water and hydrochloric acid is also called as ____.
(iii) ____agent converts hydrochloric acid to chlorine.
(iv) Hydrogen and chlorine reacts in presence of ____ to form hydrogen chloride.
(v) On addition of silver nitrate to hydrochloric acid _____precipitate is formed which is soluble in
(vi) The white precipitate of lead chloride is soluble in ______
Answer
(i) 3:1 conc. HCl and conc. HNO3
(ii) Azeotropes
(iii) Oxidising
(iv) diffused sunlight
(v) silver chloride.
(vi) hot water
16. Choose the correct answer from the options given below :
(i) HCl gas can be prepared by direct combination of hydrogen and chlorine gas in presence of
(a) Direct sunlight
(b) Dark atmosphere
(c) Diffused sunlight
(d) MnO2 catalyst
(ii) Dilute hydrochloric acid solution cannot be concentrated by boiling beyond
(a) 11%
(b) 33%
(c) 44%
(d) 22%
(iii) Bleaching powder reacts with few drops of concentrated HCl to give
(a) Chlorine
(b) Calcium oxide
(c) Oxygen
(d) None of these
(iv) Which of the following statement is not correct?
(a) HCl gas is collected by upward displacement of air
(b) HCl acid gives white precipitate with AgNO3.
(c) HCl gas is collected by downward displacement of air
(d) HCl acid turns phenolphthalein solution colurless
Answer
(i) Diffused sunlight
(ii) 22%
(iii) Chlorine
(iv) HCl gas is collected by the downward displacement of air.
17. Explain, why silver nitrate crystals are dissolved in distilled water and not in tap to prepare silver nitrate solution as a laboratory reagent.
Give one chemical test to distinguish between dilute hydrochloric acid and dilute sulphuric acid.
Answer
Silver nitrate crystals are dissolved in distilled water to prepare its solution and not in tap water .This is due to the reason that tap water contains chloride ions which gives white precipitate with AgNO3 solution.
Dilute hydrochloric add decomposes metallic carbonates, hydrogen carbonates tc give the corresponding metal chloride and carbon dioxide. The gas CO2 liberated with brisk effervescence while sulphuric add does not give CO2 .
18. (a) Name two gases which combine chemically to form a solid.
(b) Name a chloride which is soluble in excess of ammonium hydroxide.
(c) How will you show that hychloric acid contains both hydrogen and chlorine (other than by electrolysis)?
(d) Complete and balance the equations:
KMnO4 + HCl ⟶ ____ + ____+ ____+ 8H2O
Answer
(a) HCl and NH3 combine chemically to form a solid.
(b) Silver chloride is soluble in excess of NH4OH.
(c) On reaction with metals, hydrochloric acid forms respective chlorides and liberates hydrogen. 
19. Hydrogen chloride gas is very soluble in water. It is dissolved in water to prepare hydrochloric acid by using an anti - suction device, as shown in the diagram. Very briefly explain how this device prevents the suction of water into the flask, in which hydrogen chloride gas is produced.
Answer
20. Give reason for the following :
Dilute hydrochloric acid cannot be concentrated by distilling (boiling ) the dilute acid.
Answer
Dilute hydrochloric acid cannot be concentrated beyond 22.2% (by weight) by distillation. This is due to the fact that this mixture (77.8% water + 22.2% HCl) is an azeotropic mixture, it boils at a constant temperature of 110°C without any change in concentration.
21. Dilute hydrochloric acid is added in turn to a mixture of iron and sulphur and to the compound formed between iron and sulphur. Name the gas formed in each case.
Answer
When dilute hydrochloric acid is added to a mixture of iron and sulphur, then hydrogen gas will evolve. While, when dilute hydrochloric acid is added in turn to the compound formed between iron and sulphur the gas formed will be H2S.
22. Name the gas evolved when an oxide and concentrated hydrochloric acid are heated.
Answer
Chlorine gas is evolved when an oxide and concentrated hydrochloric acid are heated.
23. Explain, why the following statement is not correct.
Lead chloride can be prepared by adding dilute HCl to lead sulphate solution.
Answer
Lead chloride cannot be prepared by adding dilute HCl to lead sulphate solution because lead sulphate is insoluble salt. Infact it can be prepared by adding dilute HCl to lead nitrate solution since lead nitrate is soluble compound.
24. Outline the steps required to convent hydrogen chloride to anhydrous FeCl3 .Write equations for the equations involved.
Answer
Hydrogen chloride to anhydrous FeCl3 by adding hydrochloric acid to Fe2O3
Fe2O3 + 6HCl ⟶ 2FeCl3 + 3H2O
25. State what you see, when silver nitrate solution is added to dilute HCl.
Answer
When silver nitrate solution is added to dilute HCl, white precipitate of AgCl is formed and nitric acid is formed.
AgNO3 + HCl ⟶ AgCl (s) + HNO3
26. (a) What must be added to sodium chloride to prepare hydrogen chloride ?
(b) Write the equation for the reaction which takes place in question (a).
(c) what will you observe, when hydrogen chlorides mixed with ammonia ?
Answer
(a) Sulphuric acid must be added to sodium chloride to prepare hydrogen chloride. 
27. Hydrogen chloride dissolves in water to form an acidic solution.
(a) Name the experiment which demonstrates that hydrogen chloride is very soluble in water.
(b) Give three distinct tests (apart from using an indicator) you would carry out with this solution to illustrate the typical properties of an acid.
Answer
(a) Fountain experiment demonstrates that hydrogen chloride is very soluble in water.
(b) Tests for hydrogen chloride are:
- When silver nitrate solution is added to hydrochloric acid, it gives white precipitate of silver chloride.
- (When lead nitrate solution is added to it, it gives white precipitate of lead chloride.
- Concentrated hydrochloric acid when added to oxidizing agents like manganese dioxide, lead dioxide etc., it liberates chlorine gas which is a greenish yellow, pungent smelling gas.
28. Write equation for the reaction between hydrochloric acid with each of the following :
(a) Bleaching powder
(b) Lead nitrate solution
(c) Manganese dioxide
(d) Oxide of lead
Answer
29. What will you observed when concentrated HCl is added to lead (IV) oxide and warmed ?
Answer
When concentrated HCl is added to lead(IV) oxide and warmed, formation of metal chloride, water and greenish yellow chlorine gas will occur.
30 . Write balanced equation for the reaction between dilute hydrochloric acid and sodium sulphite.
Answer
Reaction between sodium sulphite and dilute hydrochloric acid is - 
31 . Write the equation for :
(a) The preparation of hydrogen chloride from sodium chloride and sulphuric acid. State whether the sulphuric acid should be concentrated of dilute.
(b) The reaction between hydrogen chloride and ammonia.
Answer
32. Name one lead compound that can be used to oxidize hydrogen chloride to chlorine.
Answer
Lead dioxide can be used to oxidize hydrogen chloride to chlorine
33. what happens when dilute hydrochloric acid is added to lead nitrate solution ?
Answer
When dilute hydrochloric acid is added to lead nitrate solution, white precipitate of lead chloride forms.
34. What happens when dilute hydrochloric acid is added to lead nitrate solution?
Answer
When dilute hydrochloric acid is added to lead nitrate solution, white precipitate of lead chloride forms. 
35 . Write balanced equation for the following reaction:
Red lead (trilead tetroxide) is warmed with concentrated hydrochloric acid .
Answer
36. A solution of hydrogen chloride in water is prepared. The following substances are added to separate portions of the solution :
|
S. No. |
Substance added |
Gas Evolved |
Odour |
|
1. |
Calcium carbonate |
- |
- |
|
2. |
Magnesium ribbon |
- |
- |
|
3. |
Manganese(IV) oxide with heating |
- |
- |
|
4. |
Sodium Sulphide |
- |
- |
Complete the table by writing the gas evolved in each case and its odour.
Answer
|
S. No. |
Substance added |
Gas Evolved |
Odour |
|
1. |
Calcium carbonate |
CO2 |
Odourless |
|
2. |
Magnesium ribbon |
H2 |
Odourless |
|
3. |
Manganese(IV) oxide with heating |
Cl2 |
Pungent |
|
4. |
Sodium Sulphide |
H2S |
Rotten egg |
37. State one reason why tap water is not used to prepare a solution of silver nitrate in the laboratory.
Answer
Silver nitrate crystals are dissolved in distilled water to prepare its solution and not in tap water. This is due to the reason that tap water contains chloride ions which gives white precipitate with AgNO3 solution.
38. Write balanced equations for the following reactions :
Copper oxide and dilute hydrochloric acid.
Manganese (IV) oxide and concentrated hydrochloric acid.
Answer
39.
(b) which property of hydrogen chloride is demonstrated by this experiment ?
(c) State the colour of the water that has entered the round - bottomed flask .
Answer
(a) Fountain experiment.
(b) This experiment demonstrates that hydrogen chloride is very soluble in water.
(c) Red
40. (a) Write a balanced equations for the reaction of zinc and dilute hydrochloric acid.
(b) State what is observed when hydrochloric acid is added to silver nitrated solution.
Answer
(a) Zn + 2HCl ⟶ ZnCl2 + H2
(b) When silver nitrate solution is added to hydrochloric acid, it gives white precipitate of silver chloride
41. (a) Of the two gases ammonia and hydrogen chloride, which is more dense. Name the method of collection of this gas.
(b) Give one example of a reaction between the above two gases which produces a solid compound.
Answer
(a) Hydrogen chloride is more dense.
(b) The gas is collected by upward displacement of water.
42. (a) What is property of concentrated sulphuhric add which allows it to be used in the preparation of hydrogen chloride and nitric acid?
(b) What property of hydrogen chloride is demonstrated when it is collected by downward delivery (upward displacement)?
(c) Why is hydrogen chloride not collected over water?
Answer
(a) Sulphuric acid is although weaker then hydrochloric acid hydrochloric acid is more volatile than sulphuric acid this property makes it useful in the preparation of hydrochloric add.
(b) It is heavier then air so it is collected by downward delivery.
(c) It is soluble in water so it is not collected over water.
43. Write a fully balanced for each of the following cases :
(a) Red lead is warmed with concentrated hydrochloric acid.
(b) Magnesium metal is treated with dilute hydrochloric acid.
Answer
44. Correct the following statement :
Hydrochloric acid is prepared in the laboratory by passing hydrogen chloride directly through water.
Answer
Hydrochloric acid is not prepared directly dissolving hydrochloride gas in water because it may lead to back suction. When the delivery tube carrying HCl gas is directly immersed in water, the reverse rise of water in delivery tube is known as back suction.
To prepare hydrochloric acid from hydrogen gas, it is essential to avoid back suction and it is done by using 'inverted funnel arrangement'.
45. Choose the correct answer from the options given below:
Aqua regia is a mixture of :
(a) Dilute hydrochloric acid and concentrated nitric acid
(b) Concentrated hydrochloric acid and dilute nitric acid
(c) Cocentrated hydrochloric acid [1 part] and concentrated nitric acid [ 3 parts]
(d) Concentrated hydrochloric acid [3 parts] and concentrated nitric acid [ 1 part]
Answer
Aqua regia is a mixture of concentrated hydrochloric acid [3 parts] and concentrated nitric acid [1 part].
46. The diagram shows an apparatus for the laboratory preparation of hydrogen chloride.
(i) Identify A and B
(ii) Write the equation for the reaction
(iii) How would you check whether or not the gas jar is filled with hydrogen chloride?
(iv) What does the method of collection tell you about the density of hydrogen chloride
Answer
(i) A = conc. H2SO4 B = NaCl
(iii) When a rod dipped in ammonium hydroxide is brought near the mouth of the gas jar, dense white fumes of ammonium chloride are produced.
(iv) Hydrogen chloride is denser than air.
47. By the addition of only one solution how would you distinguish between dilute hydrochloric acid and dilute nitric acid?
Answer
Silver nitrate solution will give a white ppt. when added to dil. hydrochloric acid, and no change will be observed when it is added to dil. nitric acid.
48. Choose the correct answer from the options given below :
(i) Hydrogen chloride gas being highly soluble in water is dried by :
(a) Anhydrous calcium chloride
(b) Phosphorous pentaoxide
(c) Quick time
(d) Concentrated sulphuric acid
Answer
Being highly soluble in water, hydrogen chloride gas is dried by conc. sulphuric acid.
49. In the laboratory preparation of hydrochloric acid, HCl gas is dissolved in water.(i) Draw a diagram to show the arrangement used for the absorption of HCl in water.(ii) Why is such an arrangement necessary? Give two reasons.
(iii) Write the chemical equation for the laboratory preparation of HCl gas when the reactants are:
(a) Below 200oC
(b) Above 200oC
Answer
(i) Diagram to show the arrangement used for the absorption of HCl gas in water:
(ii) Such an arrangement is necessary to prevent back suction of water into the apparatus, and it provides a large surface area for dissolution of hydrogen chloride gas.
(iii) Balanced chemical equations for the laboratory preparation of HCl gas:
50. State one appropriate observation for each of the following
(i) Copper sulphate is treated with dilute hydrochloric acid
(ii) A few drops of dilute hydrochloric acid are added to silver nitrate solution, followed by the addition of ammonium hydroxide solution
(iii) Which gas is evolved when potassium sulphite with dilute hydrochloric acid
(iv) Concentrated HCl is made to react with manganese dioxide
(v) Action of dilute HCl or sodium sulphite
Answer
(i) Add silver nitrate solution to both solutions. Sodium chloride will form a curdy white ppt., whereas sodium nitrate will not undergo any reaction.
(ii) Hydrogen chloride gas gives thick white fumes of ammonium chloride when a glass rod dipped in ammonia solution is held near the vapours of the acid, whereas no white fumes are observed in case of hydrogen sulphide gas.
(iii) Ethene gas decolourises the purple colour of KMnO4, whereas ethane does not decolourise KMnO4 solution.
(iv) Calcium nitrate forms no ppt. even with addition of excess of NH4OH, whereas zinc nitrate forms a white gelatinous ppt. which dissolves in excess of NH4OH.
(v) Carbon dioxide gas has no effect on acidified KMnO4 or K2Cr2O7, but sulphur dioxide turns potassium permanganate from pink to colourless.
51. Study the figure given alongside and answer that questions that follow:
(i) Identify the gas Y.
(ii) What property of gas Y does this experiment demonstrate?
(iii) Name another gas which has the same property and can be demonstrated through this experiment
Answer
(i) The gas is HCl (hydrogen chloride) gas.
(ii) Extreme solubility of hydrogen chloride gas is demonstrated by the fountain experiment.
(iii) Ammonia gas is another gas which has the same property which can be demonstrated through this experiment.
52. The following questions are pertaining to the laboratory pertaining hydrogen chloride gas.
(i) Write the equation for its preparation mentioning the condition required
(ii) Name the drying agent used and justify your choice
(iii) State a safety precaution you would take during the preparation of hydrochloric acid.
Answer
(i) Equation for the laboratory preparation of hydrogen chloride gas:
(ii) The drying agent used in the laboratory preparation of hydrochloric acid is conc. sulphuric acid.
The other drying agents such as phosphorus pentoxide (P2O5) and quick lime (CaO) cannot be used because they react with hydrogen chloride.
2P2O5 + 3HCl → POCl3 + 3HPO3
CaO + 2HCl → POCl3 + 3HPO3
(iii) A safety precaution which should be taken during the preparation of hydrochloric acid:
Always wear chemical splash goggles, chemical- resistant gloves and a chemical-resistant apron in the laboratory during the preparation of hydrochloric acid.
53. The aim of the fountain experiment is to prove that
(a) HCl turns blue litmus red
(b) HCl is denser than air
(c) HCl is highly soluble in water
(d) HCl fumes in moist air
Answer
(a) HCl turns blue litmus red
54. State your observations when :
(i) Dilute hydrochloric acid is added to lead nitrate solution and the mixture is heated
(ii) Dilute hydrochloric acid is added to sodium thisulphate
(iii) Dilute hydrochloric acid is added to copper carbonate
Answer
(i) When dil. HCl is added to lead nitrate solution and heated, it forms a white precipitate of lead chloride.
Pb(NO3)2 + 2HCl → PbCl2 + 2HNO3
(ii) Dil. HCl reacts with thiosulphate to produce sulphur dioxide, and yellow sulphur is precipitated.
Na2S2O3 + 2HCl → 2NaCl + H2O + SO2 + S ↓
(iii) When dilute hydrochloric acid is added to copper carbonate, it decomposes to give copper chloride.
CuCO3 + 2HCl → CuCl2 + H2O + CO2↑
55. State the observation for action of dilute hydrochloiric acid or iron (II) sulphate.
Answer
Dilute hydrochloric acid decomposes iron (II) sulphide to produce iron(II) chloride and hydrogen sulphide having rotten egg smell.
FeS + 2HCl → FeCl2 + H2S
56. How will you distinguished between dilute HCl and dilute H2SO4 using lead nitrate solution?
Answer
