JEE MAIN - Chemistry (2021 - 20th July Evening Shift - No. 19)
The vapour pressures of A and B at 25$$^\circ$$C are 90 mm Hg and 15 mm Hg respectively. If A and B are mixed such that the mole fraction of A in the mixture is 0.6, then the mole fraction of B in the vapour phase is x $$\times$$ 10$$-$$1. The value of x is ___________. (Nearest integer)
Answer
1
Explanation
xA = 0.6
PT = xAPAo + xBPBo
= 0.6 $$\times$$ 90 + 0.4 $$\times$$ 15
= 54 + 6 = 60
xAPAo = yAPT
0.6 $$\times$$ 90 = yA(60)
$$\Rightarrow$$ yA = 0.9
yB = 0.1 = 1 $$\times$$ 10$$-$$1
$$\therefore$$ x = 1
PT = xAPAo + xBPBo
= 0.6 $$\times$$ 90 + 0.4 $$\times$$ 15
= 54 + 6 = 60
xAPAo = yAPT
0.6 $$\times$$ 90 = yA(60)
$$\Rightarrow$$ yA = 0.9
yB = 0.1 = 1 $$\times$$ 10$$-$$1
$$\therefore$$ x = 1
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