Q18 / 180 · KCET 2010 · Chemistry
In which one of the following, does the given amount of chlorine exert the least pressure in a vessel of capacity $1 \mathrm{dm}^{3}$ at $273 \mathrm{~K}$ ?
- Correct answerA$0.0355 \mathrm{~g}$
- B$0.071 \mathrm{~g}$
- C$6.023 \times 10^{21}$ molecules
- D$0.02 \mathrm{~mol}$
Solution
Ideal gas equation is
$$
\mathrm{pV}=\mathrm{nRT}
$$
When $\mathrm{V}$ and $\mathrm{T}$ are same,
$$
\mathrm{p} \propto \mathrm{n}
$$
Thus, when number of moles, ie, $\mathrm{n}$ is least, it will exert least pressure.
(a) $\mathrm{n}=\frac{\mathrm{wt}}{\mathrm{mol} \text {. wt }}=\frac{0.0355}{35.5}=1 \times 10^{-3} \mathrm{~mol}$
(b) $\mathrm{n}=\frac{0.071}{35.5}=2 \times 10^{-3} \mathrm{~mol}$
(c) $\mathrm{n}=\frac{\text { number of molecules }}{\mathrm{N}_{\mathrm{A}}}$ $=\frac{6.023 \times 10^{21}}{6.023 \times 10^{23}}=0.01 \mathrm{~mol}$
(d) $\mathrm{n}=0.02 \mathrm{~mol}$
Thus, $0.0355 \mathrm{~g}$ chlorine will exert the least pressure.
Hence, the correct answer is option: 'A'.