High-temperature processing of metal sulfide ores can involve sequential reactions

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

High-temperature processing of metal sulfide ores can involve sequential reactions. Two steps used in zinc extraction are described below. Reaction X (oxidation):

2\,\text{ZnS}\,(s) + 3\,\text{O}_2\,(g) \rightarrow 2\,\text{ZnO}\,(s) + 2\,\text{SO}_2\,(g)

Reaction Y (reduction):

\text{ZnO}\,(s) + \text{CO}\,(g) \rightarrow \text{Zn}\,(l) + \text{CO}_2\,(g)

Absolute molar entropies at 1200 K are reported.

Substance	$S^\circ$ (J mol $^{-1}$ K $^{-1}$ )
$\text{ZnS}\,(s)$	75
$\text{O}_2\,(g)$	260
$\text{ZnO}\,(s)$	92
$\text{SO}_2\,(g)$	330
$\text{CO}\,(g)$	240
$\text{Zn}\,(l)$	115
$\text{CO}_2\,(g)$	310

(a) Calculate

\Delta S^\circ_{1200}

for Reaction X. (b) Calculate

\Delta S^\circ_{1200}

for Reaction Y. (c) The two reactions occur sequentially in the same furnace. Determine the cumulative

\Delta S^\circ_{1200}

for converting

2\,\text{ZnS}\,(s)

2\,\text{Zn}\,(l)

, combining stoichiometrically appropriate amounts of Reactions X and Y. (d) Given your result in part (c), assess whether the overall extraction sequence is entropy-driven at 1200 K, and discuss how this assessment could influence furnace design or operating conditions in the metallurgical industry.

Related theory

Browse the problem library