Heat and Thermodynamics 4 Question 18
20. Two non-reactive monoatomic ideal gases have their atomic masses in the ratio $2: 3$. The ratio of their partial pressures, when enclosed in a vessel kept at a constant temperature, is $4: 3$. The ratio of their densities is
(2013 Adv.)
(a) $1: 4$
(b) $1: 2$
(c) $6: 9$
(d) $8: 9$
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Solution:
- $\rho=\frac{p M}{R T} \quad \therefore \quad \rho \propto p M$
or $\quad \frac{\rho _1}{\rho _2}=\left(\frac{p _1}{p _2}\right)\left(\frac{M _1}{M _2}\right)=\left(\frac{2}{3}\right)\left(\frac{4}{3}\right)=\frac{8}{9}$
