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For the reaction :
$CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(l)$
$\Delta H_r = -170.8$ kJ mol$^{-1}$
Which of the following statements is not true :-
$CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(l)$
$\Delta H_r = -170.8$ kJ mol$^{-1}$
Which of the following statements is not true :-
A
At equilibrium, the concentrations of $CO_2(g)$ and $H_2O(l)$ are not equal
B
The equilibrium constant for the reaction is given by $K_P = \dfrac{[CO_2]}{[CH_4][O_2]}$
C
Addition of $CH_4(g)$ or $O_2(g)$ at equilibrium will cause a shift to the right
D
The reaction is exothermic
Detailed Solution
In the expression of the equilibrium constant, each concentration (or partial pressure) is raised to the power of its stoichiometric coefficient, and pure liquids and solids are left out.
For $CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(l)$, the coefficient of $O_2$ is 2 and $H_2O$ is a pure liquid.
So the correct expression is $K_P = \dfrac{p_{CO_2}}{p_{CH_4}\,(p_{O_2})^2}$
The expression given, $\dfrac{[CO_2]}{[CH_4][O_2]}$, does not have the square on the oxygen term, so that statement is not true.
$\Delta H_r$ is negative, so the reaction is exothermic; that statement is true.
By Le Chatelier's principle, adding a reactant ($CH_4$ or $O_2$) shifts the equilibrium to the right; that statement is true.
The concentrations of gaseous $CO_2$ and liquid $H_2O$ are not equal; that statement is also true.
For $CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(l)$, the coefficient of $O_2$ is 2 and $H_2O$ is a pure liquid.
So the correct expression is $K_P = \dfrac{p_{CO_2}}{p_{CH_4}\,(p_{O_2})^2}$
The expression given, $\dfrac{[CO_2]}{[CH_4][O_2]}$, does not have the square on the oxygen term, so that statement is not true.
$\Delta H_r$ is negative, so the reaction is exothermic; that statement is true.
By Le Chatelier's principle, adding a reactant ($CH_4$ or $O_2$) shifts the equilibrium to the right; that statement is true.
The concentrations of gaseous $CO_2$ and liquid $H_2O$ are not equal; that statement is also true.