Page |1
Sulphurdioxide, Sulphuric acid and
Hydrogen sulphide
Q.1.
i.
ii.
iii.
iv.
v.
vi.
vii.
Give equations for the following conversions:
a.
Sulphur dioxide to Sulphur
b.
Sulphur dioxide to sodium sulphite
c.
sodium sulphite to Sulphur dioxide.
Write the equation for the laboratory preparation of Sulphur dioxide from sodium sulphite.
a.
How is the SO2 collected?
b.
What does the method of collection tell you about the density of SO 2?
c.
What do you see when SO2 is bubbled through an acidified K2Cr2O7 solution?
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.
When burning Sulphur [i.e. SO2] reacts with H2O, a compound is formed. Name the
compound.
Give the balanced equation for reaction between SO 2 and moist Cl2.
Write a balanced equation for: SO2 and sodium hydroxide solution. [formation of normal
salt].
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.
Ans.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
(a) 2Mg [heated] + SO2 → 2MgO + S.
(b) 2NaOH SO2 → Na2SO3 + H2O.
(c) Na2SO3+ H2SO4 → Na2SO4 + H2O + SO2
Na2SO3 + 2HCl → 2NaCl + H2O + SO2.
(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.
(a) 2HNO3 + SO2 → 2NO2 + H2SO4.
(b) 2Mg [heated] + SO2 → 2MgO + S.
(c) H2O + SO2 → H2SO3.
sulphurous acid.
SO2 + Cl2 + 2H2O → 2HCl + H2SO4.
2NaOH + SO2 → Na2SO3 + H2O.
Any mineral acid HCl, H2SO4 or HNO3.
Na2O + SO2 → Na2SO3.
Q. 2
i.
Give one similarity and two differences between bleaching action of SO 2 gas and chlorine
gas.
Page |2
ii.
iii.
iv.
v.
vi.
vii.
From the following gases – ammonia, chlorine, hydrogen chloride, Sulphur dioxide, select
the gas that matches the description given below and answer the questions that follow:
Gas A is a reducing agent which contains oxygen.
(a) What is the name of the gas A?
(b) What would you observe if gas A is bubbled through acidified potassium dichromate
solution.
Write the observations and balanced equations for the reaction: A paper dipped in
potassium permanganate solution is put on the mouth of a test-tube containing Sulphur
dioxide gas.
From the gases – ammonia, hydrogen chloride, hydrogen sulphide, Sulphur dioxide –
select the following:
(a) This gas can be oxidized to Sulphur.
(b) This gas decolourises potassium permanganate solution.
(c) This gas can be obtained by the reaction between copper and concentrated sulphuric
acid.
The bleaching action of Cl2 is permanent whereas the bleaching action of SO2 is
temporary.
(a) Give a reason why chlorine is not used to bleach silk.
(b) State the similarity in the use of Sulphur dioxide and chlorine as bleaching agent.
(c) Explain the bleaching action of Sulphur dioxide with the help of chemical equations.
(d) Why is bleaching by Sulphur dioxide only temporary.
State what is observed when Sulphur dioxide is passed through a jar containing bromine
water.
Give a reason why Sulphur dioxide is used as an antichlor.
Ans.
i.
Chlorine
Sulphur dioxide
Similarity : Presence of
moisture is essential for
bleaching.
Cl2 + H2O → HCl + HOCl
SO2 + 2H2O → H2SO4 +
[H]
Dissimilarity
1. Bleaches by oxidation.
1. Bleaches by
reduction.
2. Bleaching is permanent.
2. Bleaching is
temporary.
3. Strong bleaching agent.
3. Mild bleaching agent.
ii.
iii.
iv.
v.
vi.
Sulphur dioxide.
Orange coloured acidified potassium dichromate solution changes to green.
Pink colour of paper is disappeared.
2KMnO4 + 2H2O + 5SO2 → 2MnSO4 + K2SO4 + 2H2SO4.
Hydrogen sulphide.
Sulphur dioxide.
Sulphur dioxide.
Chlorine damages the silk.
Both act as bleaching agents in presence of moisture.
Page |3
SO2 (g) + 2H2O → H2SO4 (aq.) + 2[H]
2[H] + colouring matter → Colourless matter.
Because oxygen present in air oxidizes the reduced dye.
vii.
Red colour of bromine water disappears.
viii.
Sulphur dioxide acts as a reducing agent, reduces halogens to hydrogen halides.
SO2 + 2H2O + Cl2 → 2HCl + H2SO4.
Q.3.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
Name the oxide of Sulphur which reacts with water to give sulphuric acid.
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?
(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.
(a) Name the catalyst used industrially which speeds up the conversion of SO 2 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 SO 3 and sulphuric acid.
State the name of the process by which H2SO4 is manufactured. Name the catalyst used.
Name the catalyst which helps in the conversion of Sulphur dioxide to Sulphur trioxide.
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.
Name the process used for the large scale manufacture of sulphuric acid.
Ans.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
Q.4.
Sulphur trioxide.
Concentrated sulphuric acid. Oleum or Pyrosulphuric acid.
(a) To manufacture sulphuric acid.
(b) Vanadium pentaoxide or platinised asbestos.
(c)
V2O2
2SO2 + O2 → 2SO3
450ºC
(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.
H2SO4 is manufactured by Contact Process. The catalyst used in the process is Vanadium
pentaoxide or Platinised asbestos.
Vanadium pentaoxide or Platinised asbestos.
SO3 + H2SO4 → H2S2O7 (Oleum).
H2S2O7 + H2O → 2H2SO4.
Contact Process.
Page |4
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
Write correctly balanced equation for the reaction between Iron and dilute sulphuric acid.
Write correctly balanced equations for the reaction of dilute sulphuric acid with each of
the following
(a) Copper carbonate
(b) Lead nitrate solution
(c) Zinc hydroxide.
Write a balanced equation for the reaction between zinc and dilute sulphuric acid.
Write equation for
(a) Dilute H2SO4 – producing H2.
(b) Between Pb(NO3)2 solution and dil. H2SO4.
State the substance/s reacted with dilute or concentrated sulphuric acid to form the
following gases:
(a) Hydrogen (b) Carbon dioxide.
State whether the acid used in each case is dilute or concentrated.
Write the equation for the laboratory preparation of:
(a) Sodium sulphate using dilute sulphuric acid.
(b) Lead sulphate using dilute sulphuric acid.
Write balanced equation for the reaction between
(a) Potassium hydrogen carbonate and dilute sulphuric acid.
(b) Sodium nitrate and concentrate sulphuric acid.
What do you see when concentrated sulphuric acid is added to copper sulphate-5-water.
“Concentrated sulphuric acid is used in the laboratory preparation of nitric acid and
hydrochloric acid because it is ________ [less volatile / stronger] in comparison to these
two acids.”
Write the equations for the laboratory preparation of the following salts using sulphuric
acid.
(a) Copper sulphate from copper.
(b) Lead sulphate from lead nitrate.
Choose the property of sulphuric acid (A, B, C or D), which is relevant to each of the
preparations [a] to [c]
A: Dil. acid (typical acid properties), B: Non-volatile acid, C: Oxidizing agent, D:
Dehydrating agent.
(a) Preparation of hydrogen chloride.
(b) Preparation of ethane from ethanol.
(c) Preparation of copper sulphate from copper oxide.
Which property of sulphuric acid accounts for its use as a dehydrating agent.
Concentrated sulphuric acid is both an oxidizing agent and a non-volatile acid. Write one
equation each to illustrate the above mentioned properties of sulphuric acid.
Ans.
i.
ii.
iii.
iv.
v.
vi.
Fe + H2SO4 (dil.) → FeSO4 + H2.
(a) CuCO3 + H2SO4 (dil.) → CuSO4 + H2O + CO2.
(b) Pb(NO3)2 + H2SO4 (dil.) → PbSO4 ↓ + 2HNO3.
(c) Zn(OH)2 + H2SO4 (dil.) → ZnSO4 + 2H2O.
Zn + H2SO4 (dil.) → ZnSO4 + H2.
(a) Zn + H2SO4 (dil.) → ZnSO4 + H2.
(b) Pb(NO3)2 + H2SO4 (dil.) → PbSO4 ↓ + 2HNO3.
(a) Active metals like Zn or Fe with dilute sulphuric acid.
(b) Carbonates or bicarbonates of metals with dilute sulphuric acid.
(a) Na2O + H2SO4 (dil.) → Na2SO4 + H2O.
2NaOH + H2SO4 (dil.) → Na2SO4 + 2H2O.
Na2SO3 + H2SO4 (dil.) → Na2SO4 + H2O + SO2.
2NaHSO3 + H2SO4 (dil.) → Na2SO4 + 2H2SO4 + 2SO2.
(b) Pb(NO3)2 + H2SO4 (dil.) → 2HNO3 + PbSO4 ↓
Page |5
vii.
viii.
ix.
x.
xi.
xii.
xiii.
(a) 2KHCO3 + H2SO4 (dil.) → K2SO4 + 2H2O + 2CO2.
(b) NaNO3 + H2SO4 (conc.) → NaHSO4 + HNO3 (vap.)
H2SO4
CuSO4.5H2O → CuSO4 + 5H2O.
[blue hydrous] [conc.] [white anhydrous]
Less volatile.
(a) Cu + 2H2SO4 (conc.) → CuSO4 + 2H2O + SO2.
(b) Pb(NO3)2 + H2SO4 → 2HNO3 + PbSO4 ↓.
(a) B (non-volatile acid). (b) D (dehydrating agent). (c) A (dilute acid).
Sulphuric acid’s high affinity for water accounts for its use as a dehydrating agent.
Oxidizing agent :
S + 2H2SO4 (conc.) → 3SO2 + 2H2O.
Non volatile acid :
2NaNO3 + H2SO4 (conc.) → Na2SO4 + 2HNO3.
Q.4.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
Write correctly balanced equation for the reaction between Iron and dilute sulphuric acid.
Write correctly balanced equations for the reaction of dilute sulphuric acid with each of
the following
(a) Copper carbonate
(b) Lead nitrate solution
(c) Zinc hydroxide.
Write a balanced equation for the reaction between zinc and dilute sulphuric acid.
Write equation for
(a) Dilute H2SO4 – producing H2.
(b) Between Pb(NO3)2 solution and dil. H2SO4.
State the substance/s reacted with dilute or concentrated sulphuric acid to form the
following gases:
(a) Hydrogen (b) Carbon dioxide.
State whether the acid used in each case is dilute or concentrated.
Write the equation for the laboratory preparation of:
(a) Sodium sulphate using dilute sulphuric acid.
(b) Lead sulphate using dilute sulphuric acid.
Write balanced equation for the reaction between
(a) Potassium hydrogen carbonate and dilute sulphuric acid.
(b) Sodium nitrate and concentrate sulphuric acid.
What do you see when concentrated sulphuric acid is added to copper sulphate-5-water.
“Concentrated sulphuric acid is used in the laboratory preparation of nitric acid and
hydrochloric acid because it is ________ [less volatile / stronger] in comparison to these
two acids.”
Write the equations for the laboratory preparation of the following salts using sulphuric
acid.
(a) Copper sulphate from copper.
(b) Lead sulphate from lead nitrate.
Choose the property of sulphuric acid (A, B, C or D), which is relevant to each of the
preparations [a] to [c]
A: Dil. acid (typical acid properties), B: Non-volatile acid, C: Oxidizing agent, D:
Dehydrating agent.
(a) Preparation of hydrogen chloride.
(b) Preparation of ethane from ethanol.
(c) Preparation of copper sulphate from copper oxide.
Which property of sulphuric acid accounts for its use as a dehydrating agent.
Concentrated sulphuric acid is both an oxidizing agent and a non-volatile acid. Write one
equation each to illustrate the above mentioned properties of sulphuric acid.
Page |6
Ans.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
Fe + H2SO4 (dil.) → FeSO4 + H2.
(a) CuCO3 + H2SO4 (dil.) → CuSO4 + H2O + CO2.
(b) Pb(NO3)2 + H2SO4 (dil.) → PbSO4 ↓ + 2HNO3.
(c) Zn(OH)2 + H2SO4 (dil.) → ZnSO4 + 2H2O.
Zn + H2SO4 (dil.) → ZnSO4 + H2.
(a) Zn + H2SO4 (dil.) → ZnSO4 + H2.
(b) Pb(NO3)2 + H2SO4 (dil.) → PbSO4 ↓ + 2HNO3.
(a) Active metals like Zn or Fe with dilute sulphuric acid.
(b) Carbonates or bicarbonates of metals with dilute sulphuric acid.
(a) Na2O + H2SO4 (dil.) → Na2SO4 + H2O.
2NaOH + H2SO4 (dil.) → Na2SO4 + 2H2O.
Na2SO3 + H2SO4 (dil.) → Na2SO4 + H2O + SO2.
2NaHSO3 + H2SO4 (dil.) → Na2SO4 + 2H2SO4 + 2SO2.
(b) Pb(NO3)2 + H2SO4 (dil.) → 2HNO3 + PbSO4 ↓
(a) 2KHCO3 + H2SO4 (dil.) → K2SO4 + 2H2O + 2CO2.
(b) NaNO3 + H2SO4 (conc.) → NaHSO4 + HNO3 (vap.)
H2SO4
CuSO4.5H2O → CuSO4 + 5H2O.
[blue hydrous] [conc.] [white anhydrous]
Less volatile.
(a) Cu + 2H2SO4 (conc.) → CuSO4 + 2H2O + SO2.
(b) Pb(NO3)2 + H2SO4 → 2HNO3 + PbSO4 ↓.
(a) B (non-volatile acid). (b) D (dehydrating agent). (c) A (dilute acid).
Sulphuric acid’s high affinity for water accounts for its use as a dehydrating agent.
Oxidizing agent :
S + 2H2SO4 (conc.) → 3SO2 + 2H2O.
Non volatile acid :
2NaNO3 + H2SO4 (conc.) → Na2SO4 + 2HNO3.
Q.7.
i.
ii.
iii.
iv.
v.
Dilute sulphuric acid will produce a white precipitate when added to a solution of :
A: Copper nitrate, B: Zinc nitrate,
C: Lead nitrate, D: Sodium nitrate.
Which of the following reactions is used to prepare sulphuryl chloride.
A: Adding conc. H2SO4 to a chloride.
B: Passing SO2 through a solution of chlorine.
C: Reacting dry SO2 and dry chlorine.
D: Reacting dil. H2SO4 with a solution of chlorine.
Identify the following substances (a) Gas C has a smell like rotten eggs. (b) Gas D is
colourless gas which can be used as a bleaching agent. (c) Liquid E can be dehydrated to
produce ethane.
Write the equation for the following reaction : Sulphur dioxide and water.
Copy and complete the following table relating to an important industrial process and its
final output.
Name of
process
Inputs
Contact
process
Sulphur
dioxide +
oxygen
Catalyst
Equation for
catalyzed
reaction
Output
Page |7
vi.
vii.
viii.
ix.
Making use only of substance given : dil. Sulphuric acid, Sodium carbonate, Zinc, Sodium
sulphite, Lad, Calcium carbonate : Give equations for the reactions by which you could
obtain : (a) hydrogen (b) sulphur dioxide (c) carbon dioxide (d) zinc carbonate [2 steps
required].
What property of conc. H2SO4 is used in the action when sugar turns black in its presence.
Write the equation for (a) dil. H2SO4 and barium chloride, (b) dil. H2SO4 and sodium
sulphide.
Which property of conc. H2SO4 allows it to be used in the preparation of HCl and HNO3
acids.
Ans :
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
C : Lead nitrate.
C: Reacting dry SO2 and dry chlorine.
(a) C is hydrogen sulphide (b) D is sulphur dioxide (c) E is ethanol.
SO2 + H2O → H2SO3.
Name of
process
Inputs
Catalyst
Equation for
catalyzed
reaction
Output
Contact
process
Sulphur
dioxide +
oxygen
V2O5 or Pt
2SO2
H2SO4
+
O2 →2SO3+ ∆
(a) Zn + H2SO4 → ZnSO4 + H2 (b) Na2SO3 + H2SO4 → Na2SO4 + H2O + SO2 (c) Na2CO3 +
H2SO4 → Na2SO4 + H2O + CO2 (d) Zn + H2SO4 → ZnSO4 + H2O + SO2
ZnSO4 + CaCO3 → ZnCO3 + CaSO4.
Dehydrating agent.
(a) BaCl2 + H2SO4 → BaSO4↓ + 2HCl
(b) Na2S + H2SO4 → Na2SO4 + H2S
Less volatile or non-volatile acid with a high boiling point.