Chapter 14.3, Problem 14.2WE

From the standard entropy values in Appendix 2, calculate the standard entropy changes for the following reactions at 25°C.

(a) ${\text{CaCO}}_{\text{3}}(s)\to \text{CaO(}s\text{)}+{\text{CO}}_{\text{2}}\text{(}g{\text{)(c)H}}_{\text{2}}\text{(}g{\text{) + Cl}}_{\text{2}}(g)\to 2\text{HCl(}g\text{)}$

(b) ${\text{N}}_{\text{2}}(g)+3{\text{H}}_{\text{2}}(g)\to 2{\text{NH}}_3(g)$

Strategy Look up standard entropy values and use Equation 14.5 to calculate $\Delta S{°}_{\text{rxn}}$.Just as we did when we calculated standard enthalpies of reaction, we consider stoichiometric coefficients to be dimensionless— giving $\Delta S{°}_{\text{rxn}}$units of J/K mol.