SELINA Solutions for Class 10 Chemistry Chapter 10 - Study of Compounds C. Nitric Acid

Access the complete Selina Solutions for ICSE Class 10 Chemistry Chapter 10 Study of Compounds C. Nitric Acid at TopperLearning. Understand concepts from this chapter such as aqua regia, passive iron, aqua fortis, nitrogen fixation etc. Also, learn the properties of nitric acid and its uses with our textbook solutions.

Experts prepare our Selina concise solutions and other revision notes according to the ICSE Class 10 Chemistry syllabus. Use our effective exam preparation resources to learn in detail about dilute nitric acid and concentrated nitric acid. With convenient online 24/7 access, you can now study any time and at your own pace.

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Chapter 10 - Study of Compounds C. Nitric Acid Exercise Intext 1

Question 1

What is: (a) aqua fortis (b) aqua regia (c) Fixation of Nitrogen?

Solution 1

(a) Aqua fortis: Nitric acid is called aqua fortis. Aqua fortis means strong water. It is so called because it reacts with nearly all metals.

(b) Aqua Regia: Conc. Nitric acid (1part by volume) when mixed with conc. Hydrochloric acid (3 parts by volume) gives a mixture called aqua regia. It means Royal water.

HNO3 +3HCl Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidNOCl +2H2O +2[Cl]

(c) Fixation of Nitrogen: The conversion of free atmospheric nitrogen into useful nitrogenous compounds in the soil is known as fixation of atmospheric nitrogen.

Question 2

During thunderstorm, rain water contains nitric acid. Explain with reactions.

Solution 2

During lightning discharge, the nitrogen present in the atmosphere reacts with oxygen to form nitric oxide.

N2+ O2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2NO

Nitric oxide is further oxidized to nitrogen dioxide.

2NO +O2Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2NO2

The nitrogen dioxide dissolves in atmospheric moisture in the presence of oxygen of the air and forms nitric acid which is washed down by the rain and combines with the salt present on the surface of the earth.

4NO2+2H2O +O2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid4HNO3

Question 3

Ammonia is used in the Ostwald process.

(a) Give the source of reactants used in the process.

(b) Name the catalyst used in the process.

(c) Name the oxidising agent used in this process.

(d) What is the ratio of ammonia and air taken in this process?

(e) Why is quartz used in the process?

Solution 3

(a) A mixture of air and dry ammonia in the ratio of 10:1 by volume

(b) Platinum gauze

(c) Oxygen

(d) ammonia : dry air :: 1 : 10

(e) Quartz is acid resistant. When packed in layers, it helps in dissolving nitrogen dioxide uniformly in water.

Question 4

(a) Write a balanced chemical equation for the laboratory preparation of nitric acid.

(b) In the preparation of nitric acid from KNO3, concentrated hydrochloric acid is not used in place of concentrated sulphuric acid. Explain why?

(c) Conc. Nitric acid prepared in the laboratory is yellow in colour .Why? How is this colour removed?

(d) 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 200oC.

Solution 4

(a)Chemical equation is:

KNO3 +H2SO4 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidKHSO4 +HNO3

(b) Concentrated hydrochloric acid cannot replace Conc. Sulphuric acid for the preparation of nitric acid because hydrochloric acid is volatile acid and hence nitric acid vapours will carry HCl vapours.

(c) Conc. Nitric acid prepared in the laboratory is yellow in colour due to the dissolution of reddish brown coloured nitrogen dioxide gas in acid. This gas is produced due to the thermal dissociation of a portion of nitric acid.

4HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2H2O + 4NO2 + O2

The yellow colour of the acid is removed:

If dry air or CO2 is bubbled through the yellow acid, the acid turns colourless because it drives out NO2 from warm acid which is further oxidized to nitric acid.

By addition of excess of water, nitrogen dioxide gas dissolves in water and thus the yellow colour of the acid is removed.

(d)The temperature of the mixture of concentrated sulphuric acid and sodium nitrate should not exceed 200oC because sodium sulphate formed at higher temperature forms a hard crust which sticks to the walls of the retort and is difficult to remove. At higher temperature nitric acid may also decompose.

NaNO3 + NaHSO4 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidNa2SO4 + HNO3

 

Question 5(a)

Nitric acid cannot be concentrated beyond 68% by the distillation of dilute solution of HNO3. State the reason.

Solution 5(a)

Nitric acid forms a constant boiling mixture with water containing 68% acid. This mixture boils constantly at constant boiling point without any change in its composition. At this temperature, the gas and the water vapour escape together. Hence the composition of the solution remains unchanged. So nitric acid cannot be concentrated beyond 68% by distillation of dilute solution of HNO3.

Question 5(b)

What is passive iron? How is passivity removed?

Solution 5(b)

Iron becomes inert when reacted with nitric acid due to the formation of extremely thin layer of insoluble metallic oxide which stops the reaction.

Passivity can be removed by rubbing the surface layer with the sand paper or by treating with strong reducing agent.

Question 6

Name the product formed when :

(a) Carbon and conc. Nitric acid is heated

(b) Dilute HNO3 is added to copper.

Solution 6

(a) When carbon and conc. Nitric acid is heated the products formed are Carbon dioxide, Nitrogen dioxide and water.

C + 4HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidCO2 + 2H2O +4NO2

(b) Copper when reacts with dilute HNO3 forms Copper nitrate, Nitric oxide and water.

3Cu + 8 HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid3Cu(NO3) 2 +4H2O + 2NO

Question 7

Give two chemical equations for each of the following:

(a) Reactions of nitric acid with non-metals.

(b) Nitric acid showing acidic character.

(c) Nitric acid acting as oxidizing agent.

Solution 7

(a) Reaction of nitric acid with non-metals:

C + 4HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidCO2 + 2H2O + 4 NO2

S + 6 HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidH2SO4 + 2H2O + 6 NO2

(b) Nitric acid showing acidic character:

K2O + 2HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2KNO3 + H2O

ZnO + 2HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidZn(NO3)2 + H2O

(c) Nitric acid acting as oxidizing agent

P4 +20HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid4H3PO4 + 4H2O + 20NO2

3Zn +8HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid3Zn(NO3)2 +4H2O +2NO

Question 8

Write the balanced equations and name the products formed when :

(a) Sodium hydrogen carbonate is added to nitric acid.

(b) Cupric oxide reacts with dilute nitric acid.

(c) Zinc reacts with dilute nitric acid.

(d) Concentrated nitric acid is heated.

Solution 8

(a) When Sodium hydrogen carbonate is added to nitric acid sodium nitrate, carbon dioxide and water is formed.

NaHCO3 + HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidNaNO3 +H2O +CO2

(b) When Cupric oxide reacts with dilute nitric acid, it forms Copper nitrate.

CuO +2HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidCu(NO3)2 +H2O

(c) Zinc reacts with nitric acid to form Zinc nitrate, nitric oxide and water.

3 Zn +8HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid3Zn(NO3)2 +4H2O +2NO

(d) 4HNO3Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2H2O + 4NO2 + O2

Question 9

How will you prepare the following from nitric acid?

(a) Sodium nitrate

(b) Copper nitrate

(c) Lead nitrate

(d) Magnesium nitrate

(e) Ferric nitrate

(f) Aqua regia

Solution 9


(a) Sodium nitrate:

NaOH + HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidNaNO3 +H2O

Sodium hydroxide reacts with nitric acid to form sodium nitrate.

(b) Copper nitrate:

CuO + 2HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidCu(NO3)2 + H2O

Copper oxide reacts with nitric acid to form copper nitrate.

(c) Lead nitrate:

Pb +4HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidPb(NO3)2 +2H2O +2NO2

Lead reacts with conc. nitric acid to form lead nitrate.

(d) Magnesium nitrate:

Mg +2HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidMg(NO3)2 +H2

Magnesium with dil. nitric acid to form magnesium nitrate.

(e) Ferric nitrate:

Fe + 6HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidFe(NO3)3 +3H2O + 3NO2

Iron reacts with conc. nitric acid to form ferric nitrate.

(f) Aqua regia:

HNO3 + 3HCl Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidNOCl +2H2O +2[Cl]

Nitric acid reacts with hydrochloric acid to form a mixture called aqua regia.

Question 10

Write the equation for following conversions A, B , C and D.

Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

Solution 10

A: Copper can be converted into copper nitrate.

3Cu + 8HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid3Cu(NO3)2 + 4H2O+ 2NO

B:2Cu(NO3)2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2CuO + 4NO2 + O2

C:2Cu+ O2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2CuO

D:By reduction

2CuO + C Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2Cu + CO2

Question 11

Correct the following , if required:

(a) HNO3 is a strong reducing agent.

(b) NaNO3 gives NO2 and O2 on heating.

(c) Constant boiling nitric acid contains 80% nitric acid by weight.

(d) Nitric acid remains colourless even when exposed to light.

Solution 11

(a) HNO3 is strong oxidizing agent.

(b) NaNO3 gives NaNO2 and oxygen on heating.

(c) Constant boiling nitric acid contains 68% nitric acid by weight.

(d) Nitric acid turns yellow solution when exposed to light.

Chapter 10 - Study of Compounds C. Nitric Acid Exercise Ex. 10

Question 1

Choose the correct answer:

(a) The nitrate salt which does not give a mixture of NO2 and O2 on heating is:

(i) AgNO3

(ii) KNO3

(iii) Cu(NO3)2

(iv) Zn(NO3)2

(b) The chemical used in the brown ring test is:

(i) CuSO4

(ii) FeSO4

(iii) Fe2(SO4)3

(iv) ZnSO4

(c) Lead nitrate decomposes on heating to give:

(i) NO

(ii) N2O

(iii) NO2

(iv) N2O5

Solution 1

(a)KNO3

(b) FeSO4

(c) NO2

Question 2

Name:

(a) A nitrate of metal which on heating does not give nitrogen dioxide.

(b) A nitrate which on heating leaves no residue behind.

(c) A metal nitrate which on heating is changed into metal oxide.

(d) A metal nitrate which on heating is changed into metal.

(e) A solution which absorbs nitric oxide.

(f) The oxide of nitrogen which turns brown on exposure to air. How is it prepared?

Solution 2

(a) Sodium nitrate

2NaNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2NaNO2 +O2

(b) A nitrate which on heating leaves no residue behind- Ammonium nitrate.

(c) A metal nitrate which on heating is changed into metal oxide- Calcium nitrate

(d) A metal nitrate which on heating is changed into metal- Silver nitrate

(e) A solution which absorbs nitric oxide- Freshly prepared ferrous sulphate

(f) The oxide of nitrogen which turns brown on exposure to air. - nitric oxide

By catalytic oxidation of ammonia.

4 NH3 + 5 O2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid4 NO + 6 H2O + Heat

Question 3

Mention three important uses of nitric acid. Give the property of nitric acid involved in the use.

Solution 3

Three important uses of Nitric acid and the property of nitric acid involved is:

S.NO.

Use

Property

1.

To etch designs on copper and brassware.

Nitric acid act as solvent for large number of metals.

2.

To purify gold.

Impurities like Cu, Ag, Zn, etc. dissolve in nitric acid.

3.

Preparation of aqua regia.

Dissolves noble metals.

Question 4

(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 for testing the nitrate radical in the brown ring test?

Solution 4

(a) Brown ring test

Procedure:

(i) Add freshly prepared saturated solution of iron (II)sulphate to the aq. solution of nitric acid.

(ii) Now add conc. Sulphuric acid carefully from the sides of the test tube, so that it should not fall drop wise in the test tube.

(iii) Cool the test tube in water.

(iv) A brown ring appears at the junction of the two liquids.

Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

 

Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

(b)A freshly prepared ferrous sulphate solution is used because on exposure to the atmosphere, it is oxidized to ferric sulphate which will not give the brown ring.

Question 5

From the following list of substances, choose one substance in each case which matches the description given below:

Ammonium nitrate, Calcium hydrogen carbonate, copper carbonate, lead nitrate, potassium nitrate, sodium carbonate, sodium hydrogen carbonate, zinc carbonate.

(a) A nitrate which gives off only oxygen when heated.

(b) A nitrate which on heating decomposes into dinitrogen oxide (nitrous oxide) and steam.

(c) A nitrate which gives off oxygen and nitrogen dioxide when heated.

Solution 5

(a) Potassium nitrate

(b) Ammonium nitrate

(c) Lead nitrate

Question 6

The action of heat on the blue crystalline solid X gives a reddish brown gas Y, a gas which re-lights a glowing splint and leaves a black residue. When gas Z, which has a rotten egg smell, is passed through a solution of X, a black ppt. is formed.

a. Identify X, Y and Z.

b. Write the equation for action of heat on X.

c. Write the equation between solution X and gas Z.

Solution 6

a. X is copper nitrate.

Y is nitrogen dioxide.

Z is hydrogen sulphate.

b. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

c. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

Question 7

X, Y and Z are three crystalline solids which are soluble in water and have common anion.

To help you to identify X, Y and Z you are provided with the following experimental observations. Copy and complete the corresponding inferences in (a) to (f).

(a) A reddish -brown gas is obtained when X, Y and Z are separately warmed with concentrated sulphuric acid and copper turning added to the mixture.

Inference 1: The common anion is the _____ion.

(b) When X is heated, it melts and gives off only one gas which re-lights a glowing splint.

Inference2: The cation in X is either _____ or _____.

(c) The action of heat on Y produces a reddish brown gas and yellow residue which fuses with glass of the test tube.

Inference3: The metal ion present in Y is the____ ion.

(d) When Z is heated, it leaves no residue. Warming Z with sodium hydroxide solution liberates a gas which turns moist red litmus paper blue.

Inference4: Z contains the ____ cation.

(e) Write the equations for the following reactions:

(1)X and concentrated sulphuric acid (below 200oC). (One equation only for either of the cations given in Inference 2)

(2)Action of heat on Y.

(3) Concentrated nitric acid is added to copper turnings kept in a beaker.

Solution 7

(a) Nitrate.

(b) Sodium or potassium

(c) Lead

(d) Ammonia

(e) (1)KNO3 + H2SO4 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidKHSO4 + HNO3

     (2) 2Pb(NO3)2 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid2PbO + 4NO2 +O2

     (3) Cu +4HNO3 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric AcidCu(NO3)2 +H2O +2NO2

Question 8

a. Dilute nitric acid is generally considered a typical acid except for its reaction with metals. In what way is dilute nitric acid different from other acids when it reacts with metals?

b. Write the equation for the reaction of dilute nitric acid and conc. nitric acid with copper.

Solution 8

a. 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.

b. 

 i. Reaction of dilute nitric acid with copper:

  3Cu + 8HNO3 3Cu(NO3) + 4H2O + 2NO

 ii. Reaction of conc. nitric acid with copper:

 Cu + 4HNO3Cu(NO3) + 2H2O + 2NO2

Question 9

Explain why:

a. Only all-glass apparatus should be used for the preparation of nitric acid by heating concentrated sulphuric acid and potassium nitrate.

b. Nitric acid is kept in a reagent bottle for a long time.

Solution 9

a. The glass apparatus is purposely used because nitric acid vapours are highly corrosive in nature and corrode cork, rubber etc. if used as a stopper.

b. Pure nitric acid is unstable to heat or sunlight. In the presence of sunlight, it decomposes even at room temperature.

 Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

 Nitric acid stored in a bottle turns yellow. This colour is due to dissolved NO2 in HNO3. To avoid decomposition, nitric acid is normally stored in coloured bottles.

Question 10

The figure given below illustrates the apparatus used in the laboratory preparation of nitric acid.

Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

a. Name A (a liquid), B (a solid) and C (a liquid). (Do not give the formulae).

b. Write an equation to show how nitric acid undergoes decomposition.

c. Write the equation for the reaction in which copper is oxidised by concentrated nitric acid.

Solution 10

a. A (a liquid): Conc.  sulphuric acid

B (a solid): Sodium nitrate

C (a liquid): Nitric acid

b. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

c. 

i. Reaction of dilute nitric acid with copper:

  3Cu + 8HNO3 3Cu(NO3) + 4H2O + 2NO

ii. Reaction of conc. nitric acid with copper:

  Cu + 4HNO3 Cu(NO3) + 2H2O + 2NO2

Question 11

a. A dilute acid B does not normally give hydrogen when reacted with metals but does give a gas when reacts with copper. Identify B. Write the equation with copper.

b. Complete the table:

Name of Process

Inputs

Equation

Output

 

Ammonia + Air

 

Nitric acid

 

c. What is the property of nitric acid which allows it to react with copper?

Solution 11

a. The dilute acid is nitric acid.

 Reaction of dilute nitric acid with copper:

 3Cu + 8HNO3 3Cu(NO3) + 4H2O + 2NO

b. 

Name of Process

Inputs

Equations

Output

Ostwald process

Ammonia + Air

Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

Nitric acid

 

c. Its oxidising property allows it to react with copper.

Question 2012

a. Name the gas produced when copper reacts with conc. HNO3.

b. State your observation: Zinc nitrate crystals are strongly heated.

c. Correct the statement: Magnesium reacts with nitric acid to liberate hydrogen gas.

d. Iron is rendered passive with fuming HNO3. Give reason.

e. Give the balanced equation for dilute nitric acid and copper carbonate.

Solution 2012

a. Nitrogen dioxide gas is produced when copper reacts with conc. HNO3.

b. When zinc nitrate crystals are strongly heated, they decompose into yellow-coloured zinc oxides and nitrogen dioxides, and oxygen gas is liberated.

c. Very dilute (about 1%) acid reacts with magnesium at room temperature to give magnesium nitrate and hydrogen gas.

d. Iron is rendered passive with fuming HNO3. This is due to the formation of insoluble metallic oxide which stops the reaction.

e. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

Question 2013

a. Identify the gas evolved when

 i. Sulphur is treated with conc. nitric acid.

 ii. A few crystals of KNO3 are heated in a hard glass test tube.

b. State two relevant observations for: Lead nitrate crystals are heated in a hard glass test tube.

c. Give a balanced equation for: Oxidation of carbon with conc. HNO3.

Solution 2013

a. 

 i. When sulphur is treated with conc. nitric acid, it produces nitrogen dioxide gas.

 ii. When a few crystals of KNO3 are heated in a hard glass test tube, it decomposes to form KNO2, and O2 gas is librated.

b. First, it decomposes with slight decrepitation, and second, it is reddish brown in colour when hot. After cooling, it turns yellow and fuses in glass.

c. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

Question 2014

a. Fill in the blank:

 Cold dil. nitric acid reacts with copper to form (hydrogen, nitrogen dioxide, nitric oxide).

b. Give balanced equations for the following:

 i. Laboratory preparation of nitric acid.

 ii. Action of heat on a mixture of copper and nitric acid.

Solution 2014

a. Nitric oxide

b. 

 i. Selina Solutions Icse Class 10 Chemistry Chapter - Study Of Compounds C Nitric Acid

 ii. Reaction of dilute nitric acid with copper:

3Cu + 8HNO3 3Cu(NO3) + 4H2O + 2NO Reaction of conc. nitric acid with copper:

Cu + 4HNO3 Cu(NO3) + 2H2O + 2NO2

Question 2015 (a)

(a) Identify the acid

 (i) The acid which is used in the preparation of a non-volatile acid.

 (ii) The acid which is prepared by catalytic oxidation of ammonia. 

Solution 2015 (a)

(i) Sulphuric acid 

(ii) Nitric acid 

Question 2015 (b)

State one relevant observation for each of the following:

When crystals of copper nitrate are heated in a test tube. 

Solution 2015 (b)

Reddish brown nitrogen dioxide gas is released, and the residue left behind is black copper oxide. 

Question 2015 (c)

Explain the following:

(i) Dilute nitric acid is generally considered a typical acid but not so in its reaction with metals.

(ii) Concentrated nitric add 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.

Solution 2015 (c)

(i) Dilute nitric acid is generally considered a typical acid but not in its reaction with metals, because the action of nitric acid on metals depends on the temperature and concentration of nitric acid. These conditions are not required in case of hydrochloric acid or sulphuric acid.

(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.