Which of the following choices would have a negative entropy change?

A. N2 (g) + 3H2 (g) - >2NH3 (g)

B. CaCO3 (s) - > CaO (s) + CO2 (g)

C. H2O (s) - > H2O (l)

D. Fe2O3 (s) + 3C (s) - > 2Fe (s) + 300 (g)

N2 (g) + 3H2 (g) - >2NH3 (g) denotes a negative entropy change.

Explanation:

Entropy is defined as the extent of disorder in a system. The degree of entropy is more in a gas and less in a solid.

Here, 1st reaction produces ammonia from nitrogen and hydrogen. We can see that four moles of gases produces 2 moles of gaseous product. So the degree of disorder in the system is decreasing. So the entropy is also decreasing.