Sulphuric Acid and Nitric Acid Question Answers ICSE Biology

Question .1. (i) Give equations for the following conversions:

(a) Sulphur dioxide to Sulphur

(b) Sulphur dioxide to sodium sulphite

(c) sodium sulphite to Sulphur dioxide.

(ii) (a)Write the equation for the laboratory preparation of Sulphur dioxide from sodium sulphite.

(b) How is the SO₂ collected?

(c) What does the method of collection tell you about the density of SO₂?

(d) What do you see when SO₂ is bubbled through an acidified K₂Cr₂O₇ solution?

(iii) Write one equation in each case to show the action of Sulphur dioxide as:

(a) a reducing agent

(b) an oxidizing agent

(c) an acid anhydride.

(iv) When burning Sulphur [i.e. SO₂] reacts with H₂O, a compound is formed. Name the compound.

(v) Give the balanced equation for reaction between SO₂ and moist Cl₂.

(vi) Write a balanced equation for: SO₂ and sodium hydroxide solution. [formation of normal salt].

(vii) What type of substance will liberate Sulphur dioxide from sodium sulphite.

(viii) Write the equation for the reaction by which Sulphur dioxide is converted into sodium sulphite.

Solution:

(i) (a) 2Mg [heated] + SO₂ → 2MgO + S.

(b) 2NaOH SO₂ → Na₂SO₃ + H₂O.

(c) Na₂SO₃ + H₂SO₄ → Na₂SO₄ + H₂O + SO₂

Na₂SO₃ + 2HCl → 2NaCl + H₂O + SO₂.

(ii) (a) Na₂SO₃ + 2HCl → 2NaCl + H₂O + SO₂.

(b) Sulphur dioxide is collected by upward displacement of air.

(c) Sulphur dioxide is 2.2 times heavier than air.

(d) When SO₂ is bubbled through acidified solution of K₂Cr₂O₇, the orange colour of potassium dichromate solution turns to clear green due to formation of chromium sulphate:

K₂Cr₂O₇ + H₂SO₄ + 3SO₂ → Cr₂(SO₄)₂ + H₂O.

(iii) (a) 2HNO₃ + SO₂ → 2NO₂ + H₂SO₄.

(b) 2Mg [heated] + SO₂ → 2MgO + S.

(c) H₂O + SO₂ → H₂SO₃.

(iv) sulphurous acid.

(v) SO₂ + Cl₂ + 2H₂O → 2HCl + H₂SO₄.

(vi) 2NaOH + SO₂ → Na₂SO₃ + H₂O.

(vii) Any mineral acid HCl, H₂SO₄ or HNO₃.

(viii) Na₂O + SO₂ → Na₂SO₃.

Question .3. (i) Name the oxide of Sulphur which reacts with water to give sulphuric acid.

(ii) In the Contact Process, the direct reaction between oxide of Sulphur and water is avoided. In this process, what does the oxide of Sulphur react with instead of water and what is the name of the product?

(iii) (a) What is the purpose of the Contact Process.

(b) Name the catalyst used in the Contact Process.

(c) Write the balanced equation for the reaction in the process which takes place in the presence of catalyst.

(iv) (a) Name the catalyst used industrially which speeds up the conversion of SO₂ and SO₃in the production of sulphuric acid in the laboratory or industrially.

(b) Write the equation for the conversion of Sulphur dioxide to Sulphur trioxide. Why does this reaction supply energy.

(c) What is the name of the compound formed between SO₃ and sulphuric acid.  

(v) State the name of the process by which H₂SO₄ is manufactured. Name the catalyst used.

(vi) Name the catalyst which helps in the conversion of Sulphur dioxide to Sulphur trioxide.

(vii) In the Contact Process for the manufacture of sulphuric acid, Sulphur trioxide is not converted to sulphuric acid by reacting it with water. Instead a two-step procedure is used. Write the equations for the two steps involved.

(viii) Name the process used for the large scale manufacture of sulphuric acid.

Solution:

(i) Sulphur trioxide.

(ii) Concentrated sulphuric acid. Oleum or Pyrosulphuric acid.

(iii) (a) To manufacture sulphuric acid.

(b) Vanadium pentaoxide or platinised asbestos.

(c)             V₂O₂
2SO₂ + O₂ → 2SO₃

450ºC

(iv) (a) Vanadium pentaoxide or platinised asbestos.

(b)            V₂O₂
2SO₂ + O₂ → 2SO₃

450ºC 

The reaction supplies energy as the reaction is exothermic in nature.

(c) Oleum or Pyrosulphuric acid.

(v) H₂SO₄ is manufactured by Contact Process. The catalyst used in the process is Vanadium pentaoxide or Platinised asbestos. 

(vi) Vanadium pentaoxide or Platinised asbestos.

(vii) SO₃ + H₂SO₄ → H₂S₂O₇ (Oleum).

H₂S₂O₇ + H₂O → 2H₂SO₄.

(viii) Contact Process.

 Question .6. (i) When H₂S reacts with oxidizing agents, what substance is always a product of the reaction.

(ii) State the colour of the precipitate formed when H₂S is bubbled through copper sulphate solution.

(iii) State how you can obtain H₂S from iron (II) sulphide.  

(iv) Name a gas which smells of rotten eggs.

(v) What is observed when hydrogen sulphide gas is passed through lead acetate solution.

(vi) Select the correct compound from the list given – Ammonia, Copper oxide, Copper sulphate, Hydrogen chloride, Hydrogen sulphide, Lead bromide – which matches the description given below:  The compounds smells of rotten eggs.

Solution:

(i) Sulphur.

(ii) Black precipitate of CuS.

CuSO₄ + H₂S → CuS ↓ + H₂SO₄.

(iii) Hydrogen sulphide is obtained by the action of dilute H₂SO₄ on iron (II) sulphide.

(iv) Hydrogen sulphide.

(v) When hydrogen sulphide gas is passed through lead acetate solution, black coloured precipitate of lead sulphide is formed.

Pb(CH₃COO)₂ + H₂S → PbS ↓ + 2CH₃COOH.

(vi) Hydrogen sulphide.

Question .5. (i) State why pure nitric acid takes on a yellowish brown colour when exposed to light.

(ii)  Account for the yellow colour that appears in concentrated nitric acid when it is left standing in an ordinary glass bottle.

(iii) State what is observed when nitric acid is kept in a reagent bottle for a long time.

Solution:

(i) Nitric acid takes yellowish brown colour due to the presence of dissolved nitrogen dioxide.

(ii) Nitric acid slowly decomposes even at room temperature, specially in the presence of sunlight.

4HNO₃ → 4NO₂ + 2H₂O + O₂.

Liberated nitrogen dioxide dissolves in the acid and gives a yellow colour.

(iii) Brown vapours are seen in the bottle and the nitric acid turns yellowish in colour.

Question .6. (i) State the conc. acid which will oxidize Sulphur directly to H₂SO₄. Write the equation for the same.   

(ii) Write a balanced equation for the reaction of Sulphur and hot concentrated nitric acid.

(iii) 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.

Solution:

(i) Hot and conc. nitric acid.

S + 6HNO₃ (Hot & Conc.) → H₂SO₄ + 2H₂O + 6NO₂.

(ii) S + 6HNO₃ (Hot & Conc.) → H₂SO₄ + 2H₂O + 6NO₂.

(iii) It acts as an oxidizing agent so hydrogen gas is not liberated. Instead NO gas and water are formed.

Question .7. (i) Write the equations for the reaction between copper and concentrated nitric acid.

(ii) Name a solution which gives nitrogen dioxide with copper.

(iii) Write a balanced for the reaction of conc. HNO₃ when added to copper turnings kept in a beaker.  

(iv) Write the equation for the reaction of dilute nitric acid with copper. 

Solution:

(i) Cu + 4HNO₃ (Conc.) → Cu(NO₃)₂ + 2H₂O + 2NO₂.

(ii) Nitric acid.

(iii) Cu + 4HNO₃ → Cu(NO₃)₂ + 2H₂O + 2NO₂.

(iv) 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 4H₂O + 2NO.

(vi) From the following substances, choose one in each case which matches the description given below:

Ammonium nitrate, calcium hydrogen carbonate, copper carbonate, lead 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.

(a) Potassium nitrate

(b) Ammonium nitrate

(c) Lead nitrate.