Frank Solutions for Chapter 9B Nitric Acid Class 10 Chemistry ICSE
Exercise 9B
1. How does nitric acid is formed in the atmosphere ?
Answer
Nitric acid is formed in atmosphere during lightning discharge. Nitrogen in atmosphere combine with oxygen to form nitric acid.
2. Name the following:
(i) Gas produced in air during lighting.
(ii) Gas obtained by treating manganese with 1% nitric acid.
(iii) Salt referred to as Chile saltpeter.
(iv) Salt used in the laboratory to prepare nitric add.
(v) Products obtained by the catalytic oxidation of ammonia.
(vi) Products obtained by heating concentrated nitric add.
(vii) Two coloured nitrates.
Answer
(i) Gas produced in air during lightning is Nitric Oxide.
(ii) Hydrogen gas is obtained by treating manganese with 1% nitric acid.
(iii) Salt referred to as Chile saltpeter is NaNO3.
(iv) Salt used in laboratory to prepare nitric acid is KNO3/NaNO3.
(v) Products obtained by catalytic oxidation of ammonia are NO, water& heat.
(vi) Products obtained by heating concentrated nitric acid are NO2, water & O2.
(vii) Copper nitrate is blue coloured, cobalt nitrate is coloured.
3. What is meant by the following terms ?
(a) Aqua Fortis
(b) Aqua regia
(c) Fuming nitric acid
(d) Decrepitation
Answer
(a) Aqua fortis: It is the other name far nitric add , it is also known as 'strong water'. It was called so because earlier this was the only liquid which could dissolve many metals including silver.
(b) Aqua Regia: It is a mixture of concentrated nitric add and concentrated hydrochloric add in proportion of 1:3(by volume).
(c) Fuming nano acid: It contains NO2 dissolved in concentrated HNO3.1t is obtained by distilling concentrated HNO3 with little starch.
(d) Decrepitation: It is the breaking of a substance usually accompanied by the emission of a crackling sound. An example for a substance which decrepitates on hearing is lead nitrate Pb(NO3)2
4. (a) How is nitric acid prepared in laboratory ?
(b) What is the purpose of conc. H2SO4 in the above preparation ?
(c) Why is the temperature maintained at 200°C in the above reaction ?
(d) Can we use conc. HCl in place of conc. H2SO4 ?
Answer
(a) In laboratory, nitric acid is prepared by heating a mixture of concentrated sulphuric aid and potassium cc sodium nitrate with conc. H2SO4 at 200°C.
KNO3 + H2SO4 ⟶ KHSO4 + HNO3
(b) Concentrated sulphuric acid is non-volatile and produce volatile nitric acid.
(c) The temperature is maintained at 200°C in the above reaction to avoid following problems:
- Nitric acid would decompose at high temperature.
- Potassium a sodium sulphate is formed which will stick to the walls of glass and cannot be removed be easily.
- The glass apparatus may break at high temperature.
(d) No, concentrated HO cannot be used in the place of concentrated H2SO4 because HCI is more volatile than HNO3 and hence nitric acid vapours will carry HClvapours.
5. (a) Name the process used for the manufacture of nitric acid.
(b) What are the reactants required for it and what are their sources ?
(c) In which ratio reactants are taken in this process ?
(d) Name the catalyst used in the process.
(e) What is the oxidizing agent in this process ?
(f) Write the equations involved.
Answer
(a) Ostwald process is used for used for the manufacture of nitric acid.
(b) Reactants required for Ostwald process are ammonia and oxygen of air.
(c) In ostwald process ammonia gas and air are taken in 1 : 10 ratio.
(d) Pt gauge is used as a catalyst in ostwald process.
(e) Oxygen is the oxidizing agent which converts ammonia to nitric acid. 
6. Describe the Ostwald's process for the manufacture of nitric acid with labeled diagram.
Answer
Ostwald process:
The nitric acid is manufactured by Ostwald process. In ostwald process ammonia gas and air are taken in 1:10 ratio. Pt gauge is used as a catalyst in ostwald process. Following steps are involved in Ostwald's process for the manufacture of nitric acid.
7. (a) Nitric acid cannot be concentrated beyond 68% by the distillation of a dilute solution of HNO3 State the reason.
(b) How can 68% nitric acid be concentrated to 98% nitric acid ?
Answer
(a) Nitric add cannot be concentrated beyond 68% by the distillation of a dilute solution of HNO3 because it forms an azeotropic mixture i.e. at 121°C it boils without any change in its concentration of the mixture with water.
(b) 98 % nitric acid is obtained by distilling 68% nitric acid with conc. H2SO4 under reduced pressure. The function of H2SO4 is to absorb water.
8. Give three equations of the reaction to prove that nitric acid is an acid.
Answer
Three equations to prove acidic nature of nitric acid are -
(a) Reaction with basic oxide - 
9. Mention three important uses of nitric acid; Give the property of nitric acid involved in the use.
Answer
Uses of nitric acid are-
- Nitric add is used in the purification of silver, gold, platinum etc. because impurities of other metals are dissolved in it
- Nitric add is used as an oxidiser in rocket fuel because it can supply large amount of oxygen.
- Nitric add is used in the manufacture of dyes, perfumes, drugs etc. from coal tar products since nitrobenzene is one of the raw materials of it which is manufactured from nitric acid.
10. (a) Explain with the help of a balanced equation, the brown ring test for nitric acid.
(b) Why is freshly prepared ferrous sulphate solution used in the ring test ?
(c) Brown ring disappear if the test tube is disturbed.
Answer
(a) Brown ring test:
Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated H2SO4 is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers.
(b) Freshly prepared ferrous sulphate solution is used in the ring test otherwise Ferrous sulphate undergoes aerial oxidation and converts to ferric sulphate.
(c) If the test tube is disturbed brown ring will disappear because the complex formed will get dissolved in the layers of the liquid.
11. Give reasons for the following:
(a) In laboratory preparation of nitric acid all the apparatus including cork should be made up of glass.
(b) Commercial nitric acid is yellow in colour, but when it is diluted with water, it turns colourless.
(c) Aluminum does not react with nitric acid of any concentration.
(d) Conc. Nitric acid renders iron passive.
(e) Nitric acid is used in purification of gold.
(f) Aqua regia dissolves gold and platinum.
(g) Nitric acid usually does not yield hydrogen from acids.
(h) Lighting is a blessing in disguise.
(i) Concentrated nitric acid is brown in colour.
(j) Concentrated nitric acid is a stronger oxidizing agent.
Answer
(a) In laboratory preparation of nitric acid all the apparatus including cork should be made up of glass because nitric acid vapours are highly corrosive in nature and corrodes cork, rubber etc.
(b) Commercial nitric add is yellow in colour because of presence of nitrogen dioxide but when it is diluted with water, it turns colourless because nitrogen dioxide get dissolved in water.
(c) Aluminum does not react with nitric add of any concentration because of the formation of extremely thin, unreactive, protective layer of insoluble metallic oxide on the surface of aluminium which stops further reaction.
(d) Concentrated nitric add renders iron passive because of the formation of extremely thin, unreactive, protective layer of insoluble metallic oxide on the surface which stops further reaction.
(e) Nitric acid is used in the purification of gold because impurities of other metals are dissolved in it.
(f)
(g) Nitric acid usually do not yield hydrogen gas with metals, instead it reacts with metals and form respective nitrates , nitric oxide and water.
(h) Lightning is a blessing as it is the natural source of synthesis of nitric add.
(i) Concentrated nitric acid is brown in colour due to the presence of nitrogen dioxide formed by heating the acid.
(j) Concentrated nitric acid is a stronger oxidizing agent due to nascent oxygen which it gives on decomposition.
12. Give two chemical tests for nitric acid.
Answer
Two tests for nitric acid are:
(i) Brown ring test
Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated H2SO4 is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers. 
13. Write the balanced equation for the following :
(a) Action of concentrated nitric acid on copper.
(b) Action of heat on AgNO3 .
Answer
14. Write balanced equations and name the products formed when :
(a) Sodium hydrogen carbonate is added to nitric acid.
(b) Cupric oxide reacts with nitric acid.
(c) Zinc reacts with dilute nitric acid.
(d) Concentrated nitric acid is heated.
Answer
15. How will you prepare Aqua regia from nitric acid ?
Answer
Aqua-regia is a mixture of Conc. Nitric acid and conc. Hydrochloric acid in 1 : 3. 
16. What do you observe when ?
(i) Concentrated nitric acid is dropped on a hot surface ?
(ii) Hydrogen sulphide is bubbled through conc. HNO3 ?
(iii) Conc. HNO3 drops on the skin of a person ?
(iv) Scrap zinc is heated with conc. HNO3 ?
Answer
(I) Reddish brown times of nitrogen dioxide are observed
(ii) When hydrogen sulphide is bubbled through conc.HNO3 formation of sulphur ,nitric oxide and water will occur. 
(iii) When conc. HNO3 drops al the skin of a person it reacts with the protein of the skin and forms a yellow compound called xanthoproteic add, hence skin becomes yellow. Excess of conc. HNO3 causes blisters on the skin and is highly corrosive.
(iv) When scrap zinc is heated with conc. HNO3 formation of zinc nitrate, water and nitrogen dioxide will occur. 
17. What happens when (Given balanced equation):
(a) Sulphur is added to hot and conc. HNO3 ?
(b) Nitric acid is added to KI (aq)?
(c) Nitric acid is dissolved in large amount of water?
(d) Nitric acid is added to washing soda and the resulting gas is passed through a freshly prepared lime water?
(e) Limestone reacts with nitric acid?
Answer
(a) When sulphur is added to hot and conc. HNO3 formation of oxide or oxy - acid will occur. 
18. (i) C + 4HNO3 → 2H2O + 4NO2 + CO2
(ii) 3SO2 + 2HNO3 + 2H2O → 3H2SO4 + 2NO
(iii) 3Fe + 8HNO3 (conc.) → 3Fe(NO)3 + 4H2O + 2NO
(iv) FeSO4 + NO + 5H2O → [Fe(NO)(H2O)5]SO4
(v) Pt + HNO3 + HCl → PtCl4
(vi) 2HNO3 + 6FeSO4 + 3H2SO4 → 3Fe2(SO4)3 + 2NO + 4H2O
Answer
19. Give two chemical tests to distinguish between dilute nitric acid and hydrochloric acid.
Answer
|
Dilute nitric acid |
Dilute hydrochloric acid |
|
1. On reacting copper metal with nitric acid brown fumes of nitrogen dioxide. |
1. On treating copper metal with HCl we don’t observe any reaction. |
|
2. Brown ring test : Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated H2SO4 is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers. |
2. No brown ring test is observed in the case of hydrochloric acid. |
20. Choose the correct answer from the options given below :
(i) Nitric acid on standing develops brownish colour which may be attributed to the presence of :
(a) NO2+ ions
(b) NO2- ions
(s)NO2
(d) HNO2
Answer
(a) NO2+ ions
(ii) Concentrated nitric acid oxidises phosphorus to :
(a) H3PO4
(b) P2O3
(c) H3PO2
(d) H4P2O7
Answer
(a) H3PO4
(iii) When treated with nitric acid which of the following liberate hydrogen?
(a) Zinc
(b) Magnesium
(c) Copper
(d) Mercury
Answer
(c) Magnesium
(iv) The catalyst used in the manufacture of HNO3 by Ostwald process is
(a) Platinum black
(b) Finely dividend nickel
(c) Vanadium pentoxide
(d) Platinum gauze
Answer
(d) Platinum gauze
21. Fill in the blank with appropriate word/words
(i) Aqua regia is a mixture of _______ and________
(ii) Fuming nitric acid is obtained by dissolving an excess of _______ in conc. Nitric acid
(iii) 98% nitric acid is obtained by distilling 68% nitric acid with ________ under ______
(iv) Ammonal is a mixture of _______ and __________
(v) 3 Cu + 8 HNO3 (dilute) → _______ + 4H2O + _________
Answer
(i) Aqua regia is a mixture of nitric acid and hydrochloric acid.
(ii) Fuming nitric acid is obtained by dissolving excess of nitrogen oxide in conc. nitric acid.
(iii) 98% nitric acid is obtained by distilling 68% nitric acid with conc. H2SO4 under pressure.
(iv) Ammonal is a mixture of ammonium nitrate and aluminium powder.
(v) 3Cu + 8HNO3 (dilute) → 3Cu(NO3)2 + 4H2O + 2NO
22. How would you separate gold from a mixture of gold and copper filing ?
Answer
Gold will dissolve only in aqua regia i.e., a mixture of conc. hydrochloric acid and conc. nitric acid in 1:3 but copper will dissolve in nitric acid.
To separate gold from a mixture of gold and platinum add some nitric acid to the mixture, gold will remain undissolved hence can be filtered.
23. Write balanced equation for the preparation of nitric acid from potassium nitrate.
Answer
24. Write down the word equation or balanced equation for the action of concentrated nitric acid on copper.
Answer
25. Give reasons for the following :
In the laboratory preparation of nitric acid, the mixture of concentrated sulphuric acid and sodium nitrate should not be heated very strongly, above 200°C .
Answer
In the laboratory preparation of nitric acid, the mixture of concentrated sulphuric aad and sodium nitrate should not be heated very strongly, above 200°C because a higher temperature can cause following problems:
- Nitric acid would decompose to form nitrogen dioxide.
- Sodium sulphate is formed which may stick to the glass and cannot be removed easily
- The glass apparatus may break.
26. Complete and balance the following equation :
Cu + HNO3 → NO2 + ___ + ____
Answer
27. Give reason for the following :
Commercial concentrated nitric acid is yellow in colour, but when it is dilute with water, it turns colourless.
Give one chemical test for nitric acid.
Answer
Commercial nitric and is yellow in colour because of presence of nitrogen dioxide but when it is diluted with water, it turns colourless because nitrogen dioxide gets dissolved in water.
Brown ring test can be used to test nitric acid:
Brown ring test: Nitric acid in a test tube is taken and then and then freshly prepared ferrous sulphate solution is added. Concentrated H2SO4 is then added carefully down the sides of the test tube, dark brown ring is formed at the junction of two layers.
28. State the conditions for the oxidation of ammonia to nitrogen monoxide [nitric oxide], in the manufacture of nitric acid by Ostwald's process. Write the balanced equation for the reaction.
Answer
Oxidation of ammonia in catalytic chamber. 
29. The following statement is correct only under certain conditions. Rewrite the statement including the appropriate condition(s) and underline it in your answer .
Copper and nitric acid react together to produce nitrogen dioxide.
Answer
Copper is heated with nitric acid, they react together to produce nitrogen dioxide
30. Write a balanced equation for the production of nitrogen dioxide using copper.
Answer
31. Name the product, catalyst and approximate temperature maintained in Ostwald's process. How is the temperature maintained in the Ostwald's process ?
Answer
The nitric acid is manufactured by Ostwald process. In ostwald process ammonia gas and air are taken in 1:10 ratio. Temperature is maintained at 800°C I the catalytic chamber, as the reaction is exothermic so the heat evolved maintains the temperature in the catalytic chamber.
32. Write the balanced equation for the equation preparation of nitric acid from potassium nitrate.
Answer
33. During a thunderstorm, the rainwater contains nitric acid. The nitric acid is formed as a result of three chemical reactions. Describe or write balanced chemical equation for these three reactions.
Answer
During a thunderstorm, the rainwater contains nitric acid. The nitric acid is formed as a result of three chemical reactions which is described as follows :
1. During lightning discharge, nitrogen in atmosphere combines with oxygen to form nitric oxide.
34. Give the name of a soluble lead salt and write the equation for the action of heat on this salt. Write the equation for the preparation of nitric acid from potassium nitrate.
Answer
Lead nitrate is a soluble salt. On heating lead nitrate the following reaction occurs : 
35. Write balanced equation for the reaction between nitrogen and oxygen, when lightning strikes.
Answer
36. Describe what you see when concentrated nitric acid is added to copper.
Answer
When concentrated nitric acid is added to copper brown fumes of nitrogen dioxide are observed.
37. What do you see then concentrated nitric acid is added to copper ?
Answer
When concentrated nitric acid is added to copper brown fumes of nitrogen dioxide are observed.
38. Name (formula is not acceptable) the gas produced in each of the following reactions:
(i) By the action of concentrated nitric acid on copper.
(ii) On warming ammonium sulphate with sodium hydroxide solution.
Answer
(i) Nitrogen dioxide
(ii) Ammonia gas
39. Choose the correct word from the brackets to complete the sentences :
(i) Sulphur can be converted to sulphuric acid using _____ (concentrated/dilute) nitric acid.
(ii) Write the equation for the reaction in 2(i).
Answer
(i) concentrated
(ii) S + 6HNO3 → H2SO4 + 2H2O + 6NO2
40. Write the equation to show the reactions between the following :
(i) Dilute nitric acid to produce carbon dioxide.
(ii) Between copper and concentrated nitric acid.
Answer
41. Name the compounds required for the laboratory preparation of nitric acid.
Answer
For laboratory preparation of nitric acid potassium nitrate or sodium nitrate and conc. sulphuric acid is required.
42. Why does pure nitric acid take on a yellowish brown colour when exposed to light ?
Answer
Yellowish brown colour of nitric acid is due to the presence of nitrogen dioxide formed due to thermal decomposition of nitric acid.
43. Write equations to show the reactions between the following :
(i) Copper and concentrated nitric acid
(ii) Copper oxide and dilute nitric acid
Answer
44. The first step in the manufacture of nitric acid is the catalytic oxidation of ammonia. What is the name of the catalyst ?
Answer
Platinum gauze is used as catalyst in the manufacture of nitric acid.
45. When nitric acid is prepared by the action of concentrated sulphuric acid on potassium nitrate. What is the special feature of the apparatus used ?
Answer
The apparatus used is made up of glass as nitric acid is highly corrosive in nature.
46. Write the equation for the laboratory preparation of nitric acid from potassium nitrate and concentrated sulphuric acid.
Answer
47. Write balanced equation to show the reaction between the sulphur and hot concentrated nitric acid.
Answer
48. (i) Dilute nitric add is generally considered to be a typical add except fcr its reaction with metals. In what way is dilute nitric add different from other adds when it reacts with metals?
(ii) Write the equation fur the reaction of dilute nitric add with copper.
(iii) Account for the yellow colour that appears in concentrated nitric add when it is left standing in an ordinary glass bottle.
Answer
(i) Dilute nitric add is generally considered to be a typical acid except for its reaction with metals, nitric add did not evolve hydrogen gas on reacting with any metal, other than manganese and magnesium.
(iii) In a glass apparatus nitric acid gem decomposed by sunlight .Yellowish brown colour of nitric acid is due to the presence of nitrogen dioxide formed due to thermal decomposition of nitric acid.
49. (i) Explain, why only all glass apparatus should be used for the preparation of nitric acid by heating concentrated sulphuric acid and potassium nitrate.
(ii) Write a chemical equation to illustrate the acidic nature of nitric acid.
Answer
(i) Nitric acid is highly corrosive in nature and corrodes cork, rubber, etc.
(ii) Nitric acid ionizes in water to form free hydronium ions and nitrate ions. This shows that nitric acid is acidic in nature.
50. The figure given below illustrates the apparatus used in the laboratory preparation of nitric acid : 
(i) Name A (a liquid ), B(a solid ) and C (a liquid).
(ii) Write the balanced chemical equation to show how nitric acid undergoes decomposition.
(iii) Write the balanced chemical equation for the reaction in which copper is oxidized by concentrated nitric acid.
Answer
51. State, what is observe when nitric acid is kept in a reagent bottle for a long time.
Answer
If nitric acid is kept in a bottle for long time then it will become brown in colour.
52. Write the equation for the reaction : Aluminium Nitride and water.
Answer
53. Copy and complete the following table relating to important industrial processes. Output refers to the product of the process not the intermediate steps.
|
Name of process |
Inputs |
Catalyst |
Equation for catalysed reaction |
Output |
|
Haber Process |
Hydrogen + |
|
|
|
|
|
Ammonia + Air |
|
|
Nitric acid |
Answer
|
Name of process |
Inputs |
Catalyst |
Equation for catalysed reaction |
Output |
|
Haber Process |
Hydrogen + |
Iron |
|
Ammonia |
|
Ostwald process |
Ammonia + Air |
Platinum |
|
Nitric acid |
54. Name the gas evolved :
The gas produced on heating sodium nitrate.
Answer
Oxygen gas is evolved on heating sodium nitrate.
55. (i) What is the special feature of the apparatus that is used in the laboratory preparation of nitric acid?
(ii) Why should the temperature of the reaction mixture of nitric acid not be allowed to rise above 200oC?
Answer
(i) The complete apparatus should be made of glass only.
(ii) At high temperature, nitric acid decomposes and the glass apparatus may get damaged. Sodium formed at a higher temperature forms a hard crust which sticks to the walls of the retort.
56. What would you observe in the following case :
Copper is heated with concentrated nitric acid in a hard glass test rube.
Answer
Brown fumes of nitrogen dioxide are produced. Copper reacts with concentrated nitric acid to produce copper nitrate, water and nitrogen dioxide.
57. (i) Identify the gas evolved when sulphur is treated with concentrated NH3.
(ii) Balanced equation of oxidation of carbon with concentrated HNO3
Answer
(i) When sulphur is treated with conc. nitric acid, it produces nitrogen dioxide.
(ii) 
58. Explain the following :
(i) Dilute nitric acid is generally considered a typical acid but not so in its reaction with metals
(ii) Concentrated nitric acid appears yellow when it is left standing in a glass bottle.
(iii) An all glass apparatus is used in the laboratory preparation of nitric acid.
Answer
(i) Dilute nitric acid is generally considered a typical acid except for its reaction with metals because it does not liberate hydrogen. It is a powerful oxidising agent, and nascent oxygen formed oxidises hydrogen in water.
(ii) Although pure concentrated nitric acid is colourless, it appears yellow when left standing in a glass bottle due to the dissolution of reddish brown nitrogen dioxide gas in the acid. Nitrogen dioxide is produced because of the thermal decomposition of a portion of nitric acid.
4HNO3 → 2H2O + 4NO2 + O2
(iii) An all-glass apparatus is used in the laboratory preparation of nitric acid because nitric acid vapour corrodes rubber and cork.
59. Fill in the blanks using the appropriate words given below :
(Sulphur dioxide, Nitrogen dioxide, Nitric oxide, Sulphuric acid)
(i) Cold, dilute nitric acid reacts with copper to give ______.
(ii) Hot, concentrated nitric add reacts with sulphur to form ______.
Answer
(i) Cold, dilute nitric acid reacts with copper to give nitric oxide.
(ii) Hot, concentrated nitric acid reacts with sulphur to form nitrogen dioxide.
60. Write a balanced equation for following :
(i) Action of cold and dilute nitric acid on copper
(ii) Action of conc. Nitric acid on sulphur
(iii) Reaction of ammonia with nitric acid
(iv) Laboratory preparation nitric acid.
Answer
(i) 3Cu + 8HNO3→ 3Cu(NO3)2 + 4H2O+ 2NO↑