Fig. 8.1 is a simplified flow diagram for the Contact process. Solid E is burned to make gas F, which then passes through a converter containing catalyst G....
Question 1 Report
Fig. 8.1 is a simplified flow diagram for the Contact process. Solid E is burned to make gas F, which then passes through a converter containing catalyst G.
Fig. 8.1
(a) Name solid E that is burned at the start of the process. [1]
(b) Gas F is sulfur dioxide. Write the word equation for the reaction that makes gas F. [1]
(c) In the converter, gas F reacts to form gas H. Write the balanced symbol equation for this reaction, using the reversible reaction symbol. [2]
(d) Name catalyst G used in the converter. [1]
(e) Name product J made at the end of the Contact process. [1]
(f) State the temperature used in the converter. [1]
(g) State one use of product J. [1]
Answer Details
This flow diagram is the Contact process, the industrial manufacture of sulfuric acid. Follow the substances through: burn sulfur to make sulfur dioxide, oxidise it to sulfur trioxide over a catalyst, then absorb to make the acid.
(a) Solid E [1]. The solid burned at the start is sulfur [1].
(b) Word equation for gas F [1]. sulfur + oxygen → sulfur dioxide [1].
(c) Balanced equation in the converter [2].
2SO2 + O2 ⇌ 2SO3
Award [1] for correct formulae and [1] for a balanced equation using the reversible arrow. Check: 2 S and \(4 + 2 = 6\) O on the left equal 2 S and \(2\times3 = 6\) O on the right. Gas H is sulfur trioxide.
(d) Catalyst G [1]. Vanadium(V) oxide, V2O5 [1].
(e) Product J [1]. Sulfuric acid [1].
(f) Temperature in the converter [1]. About 450 °C [1]. This is a compromise temperature, high enough for a fast rate but not so high that too much SO3 breaks back down.
(g) One use of product J [1]. Any valid use, for example making fertilisers, detergents, paints, or as the acid in car batteries [1].
Exam tip: learn the Contact process conditions as a set, catalyst V2O5, about 450 °C and around 2 atmospheres pressure, and remember the converter step is the reversible one, so it uses the ⇌ arrow.
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