Question

Predict the sign of the change in entropy for the following procosses:

1. Decomposition of carbonic acid (H2CO3) into water and carbons dioxide
2. Sublimation of naphthalene (mothballs)
3. Melting of lead metal at room temperature
4. Formation of dinitrogen tetroxide (N2O4) from nitrogen dioxide: 2NO2 - N2O4
5. Combustion of ethane (C2H6) gas: 2C2H6+7O2- 4CO2 + 6H2O

Answer 1

Entropy is a measure of the degree of randomness of disorder of a system. The natural tendency of a system is for its entropy to increase. The formula for entropy is; $\Delta_s$ $=$ $q_{rev} \over T$

Entropy increases;

• With a change of state from solid to liquid, or liquid to gaseous state, or solid to vapour.
• When a substance is broken into multiple parts
• With increase in temperature
• When the total number of product molecules is greater than the total number of reactant molecules.

In this case,entropy;

1. Increases $\Delta_s \gt0$
2. Increases $\Delta_s \gt0$
3. Increases $\Delta_s \gt0$
4. Decreases $\Delta_s \lt0$
5. Increases $\Delta_s \gt0$