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Kp for a solid decomposing into gases

This type of question, asked 3 times: 2021 Paper 17, 2021 Paper 21, 8 Apr 2026 S2. All 3 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    2021 Paper 17

    51
    The equilibrium constant for the reaction A(s)⇌M(s)+12O2( g)A(s) \rightleftharpoons M(s) +\frac{1}{2}O_{2}(\text{ }g) is Kp=4K_{p}= 4. At equilibrium, the partial pressure of O2O_{2} is ____\_\_\_\_ atm. (Round off to the nearest integer)

  2. Question 2

    2021 Paper 21

    58
    When 5.1 g5.1\text{ }g of solid NH4HSNH_{4}HS is introduced into a two litre evacuated flask at 27∘C,20%27^{\circ}C,20\% of the solid decomposes into gaseous ammonia and hydrogen sulphide. The KpK_{p} for the reaction at 27∘C27^{\circ}C is x×10−2x \times10^{- 2}. The value of xx is ____\_\_\_\_. (Integer answer) [Given R=0.082 L atm K−1 mol−1R = 0.082\text{ }L\text{ }atm{\text{ }K}^{- 1}{\text{ }mol}^{- 1} ]

  3. Question 3

    8 Apr 2026 S2

    50
    Solid carbon, CaO and CaCO3{CaCO}_{3} are mixed and allowed to attain equilibrium at T K .
    CaCO3(s)⇌CaO(s)+CO2(g),Kp1=0.08 atm{CaCO}_{3}(s) \rightleftharpoons CaO(s) + {CO}_{2}(g),\quad K_{p_{1}} = 0.08\text{ atm}
    C(s)+CO2(g)⇌2CO(g),Kp2=2 atmC(s) + {CO}_{2}(g) \rightleftharpoons 2CO(g),\quad K_{p_{2}} = 2\text{ atm}
    The partial pressure of CO is ____\_\_\_\_ ×10−1 atm\times 10^{- 1}\text{ }atm.