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Mr. Robert Zammit M.Sc.
Unit 10.2 – Sulfur & its compounds - Lesson 1 of 2 Page 1 of
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Unit 10.2:
Sulfur & its compounds Lesson 2 of 2
Sulfuric Acid
• Sulfuric acid is highly corrosive but is also a very important
substance. It is used to make fertilisers, paints, pigments, dyes,
detergents and artificial fibres amongst other products. Sulfuric
acid is also the acid used in car batteries.
• While dilute sulfuric acid is a normal diprotic acid,
concentrated sulfuric acid acts differently. Concentrated sulfuric
acid is:
Hygroscopic. If left exposed to air, it absorbs moisture and the
volume of the liquid can be seen to increase. As a result, sulfuric
acid is used as a drying agent in the laboratory preparation of
pure, dry chlorine, hydrogen chloride and sulfur dioxide.
A dehydrating agent, which means that it can take away the
elements of
water from a number of substances. These include hydrated salts
and sugar. With sugar a black mass of carbon is left.
CuSO4∙5H2O(aq) conc. H2SO4 → CuSO4(aq) + 5H2O(l)
C6H12O6(s) conc. H2SO4 → 6C(s) + 6H2O(l)
A strong oxidizing agent, getting itself reduced to sulfur
dioxide in the
process. It can, for example, oxidize copper: 2H2SO4(l) + Cu(s)
→ CuSO4(s) + SO2(g) + 2H2O(l)
A very strong acid such that it can be used to prepare other
acids. For
example, its action on chlorides: H2SO4(l) + NaCl(s) → NaHSO4(s)
+ HCl(g)
https://www.youtube.com/watch?v=aamm2EHCpBIhttps://www.youtube.com/watch?v=DhCHECcvKOAhttps://www.youtube.com/watch?v=bJBPhpqQxs8https://www.youtube.com/watch?v=aamm2EHCpBIhttps://www.youtube.com/watch?v=DhCHECcvKOAhttps://www.youtube.com/watch?v=bJBPhpqQxs8
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Mr. Robert Zammit M.Sc.
Unit 10.2 – Sulfur & its compounds - Lesson 1 of 2 Page 2 of
4
The Contact Process – Industrial Manufacture of Sulfuric
acid.
• Sulfuric acid is produced in the Contact process which is
composed of
four main steps: 1. Sulfur is burnt in a good supply of air.
S(s) + O2(g) → SO2(g)
2. Sulfur dioxide with more oxygen is heated to high
temperatures and passed over a vanadium(V) oxide (V2O5) catalyst.
This is done at a temperature of 400-450°C and a pressure of
2atm.
2SO2(g) + O2(g) ⇌ 2SO3(g)
3. If sulfur trioxide is added directly to water, sulfuric acid
will be produced. However the reaction gives a large amount of
energy, is difficult to control and results in the sulfuric acid
evaporating. Instead, sulfur trioxide is added to the recently
prepared concentrated sulfuric acid to produce oleum.
SO3(g) + H2SO4(l) → H2S2O7(l)
4. Oleum can be added to the correct amount of water to produce
sulfuric acid of the needed concentration.
H2S2O7(l) + H2O(l) → 2H2SO4(l)
By the end of this lesson you should be able to:
Recall and describe the stages in the manufacture of sulfuric
acid; recall the actual operating conditions used in the Contact
process.
Distinguish between the reactions of sulfuric acid as a dilute
acid and as a concentrated acid. Describe and explain specific
examples to show concentrated sulfuric acid to be hygroscopic,
an
oxidising agent and a dehydrating agent. Recall some uses of
sulfuric acid to illustrate its importance in industry and in
everyday life.
https://www.youtube.com/watch?v=xjLUJ-7m5v8https://www.youtube.com/watch?v=xjLUJ-7m5v8
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Mr. Robert Zammit M.Sc.
Unit 10.2 – Sulfur & its compounds - Lesson 1 of 2 Page 3 of
4
Exercise 2:
1. Fill in the blanks using words from below. Each item can be
used once, more than once or not at all.
2 450 600 Vanadium (V) oxide Hydrogen
200 Sulfur trioxide Allotropes Oxygen Water
Rhombic Monoclinic Iron Fertilisers Sulfur dioxide
Sulfur has two ___(a)___ with the most common one being yellow,
___(b)___ sulfur. The other allotrope is ___(c)___ sulfur, which
exists as amber needle like crystals. In the first stage of the
Contact process, sulfur is burned in air to form ___(d)___ . This
gas is then used in the second stage of the process. It is mixed
with ___(e)___ gas, then passed over the catalyst ___(f)___ at a
temperature of ___(g)___ ºC and ___(h)___ atmospheres pressure. The
product of this reaction is ___(i)___ gas. Finally, this gas is
absorbed in concentrated sulfuric acid forming a liquid called
‘oleum’ to which the correct amount of ___(j)___ is added in order
to obtain ordinary concentrated sulfuric acid. One use of sulfuric
acid is to make ___(k)___ .
2. Write balanced chemical equations for all the steps involved
in the Contact process.
3. These are some reactions of sulfuric acid: Reaction 1. A +
sulfuric acid → copper(II) sulfate + water Reaction 2. B + sulfuric
acid → copper(II) sulfate + water + sulfur dioxide Reaction 3. C +
sulfuric acid → sodium sulfate + water + carbon dioxide Reaction 4.
D + sulfuric acid → sodium hydrogensulfate + hydrogen chloride
Reaction 5. E + sulfuric acid → carbon + water + dil. sulfuric acid
a. Name the reagents A to E. b. State whether sulfuric acid has to
dilute or concentrated in reactions 1 to 5. c. What is the role of
sulfuric acid in reaction 2? d. What is the role of sulfuric acid
in reaction 5? e. Write balanced chemical reactions for equations 1
to 5.
4. Sulfuric acid is a strong oxidizing agent. It can oxidize
bromide ions to bromine and iodide ions to iodine. However,
sulfuric acid cannot oxidize chloride ions to chlorine. Explain why
this is so.
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Mr. Robert Zammit M.Sc.
Unit 10.2 – Sulfur & its compounds - Lesson 1 of 2 Page 4 of
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Model Answers to Exercise 2:
1) Question 1
a) allotropes b) rhombic c) monoclinic d) sulfur dioxide e)
oxygen f) vanadium(V) oxide g) 450oC h) 2 atmospheres (atm) i)
sulfur trioxide j) water k) fertilisers
2) Question 2 a) Step 1: S(s) + O2(g) → SO2(g) b) Step 2:
2SO2(g) + O2(g) ⇌ 2SO3(g) c) Step 3: SO3(g) + H2SO4(l) → H2S2O7(l)
d) Step 4: H2S2O7(l) + H2O(l) → 2H2SO4(l)
3) Question 3 a) A: copper(II) oxide (or copper(II) hydroxide);
B: copper; C: sodium carbonate (or sodium
hydrogen carbonate); D: sodium chloride; E: glucose b) 1:
dilute; 2: concentrated; 3: dilute; 4: concentrated; 5:
concentrated c) Oxidising agent (it oxidises Cu to Cu2+). d)
Dehydrating agent (removes water causing a chemical change). e)
Reaction 1: CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)
Or: Cu(OH)2(s) + H2SO4(aq) → CuSO4(aq) + 2H2O(l) Reaction 2:
Cu(s) + 2H2SO4(l) → CuSO4(s) + SO2(g) + 2H2O(l) Reaction 3:
Na2CO3(s) + H2SO4(aq) → Na2SO4(aq) + H2O(l) + CO2(g) Or: 2NaHCO3(s)
+ H2SO4(aq) → Na2SO4(aq) + 2H2O(l) + 2CO2(g) Reaction 4: NaCl(s) +
H2SO4(l) → NaHSO4(s) + HCl(g) Reaction 5: C6H12O6(s) conc. H2SO4 →
6C(s) + 6H2O(l)
4) Question 4 Sulfuric acid is a stronger oxidising agent than
Bromine and Iodine, BUT NOT chlorine. The latter is a stronger
oxidising agent than sulfuric acid.
Sulfuric AcidThe Contact Process – Industrial Manufacture of
Sulfuric acid.By the end of this lesson you should be able
to:Exercise 2:Model Answers to Exercise 2: