Question

The thermal dissociation of equilibrium of $CaCO_3$ (s) is studied under different conditions $CaCO_3 \, ( g) \rightleftharpoons CaCO ( g ) + CO_2 ( g)$ For this equilibrium, the correct statement(s) is/are

• A. $\triangle$ H is dependent on T
• B. K is independent of the initial amount of $CaCO_3$
• C. K is dependent on the pressure of $CO_2$ at a given T
• D. $\triangle$ H is independent of the catalyst, if any

Answer 1

Answer: (D)

$\triangle$ H is independent of the catalyst, if any

Answer 2

PLAN Heat of reaction is dependent on temperature (Kirchhoff's equation) in heterogeneous system, equilibrium constant is independent on the molar concentration of solid species. Heat of reaction is not affected by catalyst. It lowers activation energy. $CaCO_3 \, ( g) \rightleftharpoons CaCO ( g ) + CO_2 ( g)$ By KirchhofFs equation, $\triangle H_2^o \, (at \, T_2) = \triangle H_1^o \, (at \, T_1 ) + \triangle C_p ( T_2 - T_1 )$ $\triangle H^\circ$ varies with temperature. Thus, (a) is correct. $K = p_{ CO_2 }$ K is dependent on pressure of $CO_2$ but independent of molar concentration of $CaCO_3$, Thus, (b) and (c) are correct. At a given temperature, addition of catalysis lowers activaion energy, $\triangle$H remaining constant. Thus, (d) is also correct. $E_a$ = Activation energy in absence of catalyst $E_a$' = Activation energy in presence of catalyst