Question

The decomposition of CaCO3 in a closed vessel is represented by the equation
CaCO3 ⇌ (s) CaO (s) + CO2 (g)
Calculate the number of phases, components and degree of freedom

• A. p = 2: C=3; F = 3
• B. p = 3; C=2; F = 1
• C. p = 2: C=2; F = 2
• D. p = 3: C=3; F = 2

Answer 1

Answer: (B)

p = 3; C=2; F = 1

Answer 2

The decomposition of calcium carbonate is represented by the equilibrium: $\text{CaCO}_3\text{(s)} \rightleftharpoons \text{CaO(s)} + \text{CO}_2\text{(g)}$

1. Phases (p): There are three physically distinct and separable parts: solid CaCO$_3$, solid CaO, and gaseous CO$_2$. Thus, $p=3$.
2. Components (C): There are three chemical species (CaCO$_3$, CaO, CO$_2$) involved in one independent equilibrium reaction. The number of components is calculated as $C = (\text{number of species}) - (\text{number of independent reactions}) = 3 - 1 = 2$.
3. Degrees of Freedom (F): Using the Gibbs Phase Rule, $F = C - P + 2$. Substituting the values, $F = 2 - 3 + 2 = 1$.