For the reaction, CH_4(g) + 2O_2(g) leftharpoons CO_2(g) + 2H_2O(l) _r H = -170.8 kJ mol^-1 Which of the following statements is not true? - Chemistry MCQ Chemistry | ExamTest.live

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For the reaction, CH_{4} (g) + 2 O_{2} (g) ⇌ CO_{2} (g) + 2 H_{2} O (l) Δ_{r} H = - 170.8 kJ mol^{- 1} Which of the following statements is not true?

A $At equilibrium, the concentrations of CO_{2} (g) and water (l) are not equal.$
B $The equilibrium constant for the reaction is given by K_{p} = \frac{[ CO _{2} ]}{[ CH _{4} ] [ O _{2} ]}$
C $Addition of CH_{4} (g) or O_{2} (g) at equilibrium will cause a shift to the right$
D $The reaction is exothermic$

Solution & Step-by-step Explanation

The equilibrium constant expression for partial pressures (K_{p}) must use the partial pressures of gases, not concentrations. Moreover, the stoichiometric coefficient of O_{2} is 2, so it should be squared. The given formula K_{p} = \frac{[ CO _{2} ]}{[ CH _{4} ] [ O _{2} ]} is incorrect both in notation and power.

Try it yourself before checking the explanation above.

For the reaction, CH_{4} (g) + 2 O_{2} (g) ⇌ CO_{2} (g) + 2 H_{2} O (l) Δ_{r} H = - 170.8 kJ mol^{- 1} Which of the following statements is not true?

At equilibrium, the concentrations of CO_{2} (g) and water (l) are not equal.

The equilibrium constant for the reaction is given by K_{p} = \frac{[ CO _{2} ]}{[ CH _{4} ] [ O _{2} ]}

Addition of CH_{4} (g) or O_{2} (g) at equilibrium will cause a shift to the right

The reaction is exothermic

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