JEE MAIN - Chemistry (2021 - 27th August Evening Shift - No. 20)
When 5.1 g of solid NH4HS is introduced into a two litre evacuated flask at 27$$^\circ$$C, 20% of the solid decomposes into gaseous ammonia and hydrogen sulphide. The Kp for the reaction at 27$$^\circ$$C is x $$\times$$ 10$$-$$2. The value of x is _____________. (Integer answer) [Given R = 0.082 L atm K$$-$$1 mol$$-$$]
Answer
6
Explanation
moles of NH4HS initially taken = $${{5.1g} \over {51g/mol}}$$ = 0.1 mol
volume of vessel = 2 litre
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$$\Rightarrow$$ partial pressure of each component
$$P = {{nRT} \over V} = {{0.1 \times 0.2 \times 0.082 \times 300} \over 2}$$
= 0.246 atm
$$\Rightarrow$$ kP = P$$N{H_3}$$ $$\times$$ P$${H_2}S$$ = (0.246)2 = 0.060516
= 6.05 $$\times$$ 10$$-$$2
$$ \therefore $$ x = 6
volume of vessel = 2 litre
$$\Rightarrow$$ partial pressure of each component
$$P = {{nRT} \over V} = {{0.1 \times 0.2 \times 0.082 \times 300} \over 2}$$
= 0.246 atm
$$\Rightarrow$$ kP = P$$N{H_3}$$ $$\times$$ P$${H_2}S$$ = (0.246)2 = 0.060516
= 6.05 $$\times$$ 10$$-$$2
$$ \therefore $$ x = 6
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