Question

3.6 gm of an ideal gas was injected into a bulb of the internal volume of 8 L at pressure P atm and temp T K. The bulb was then placed in a thermostat maintained at $(T+15)$ $K$. 0.6 gm of the gas was let off to keep the original pressure.

Find P and T if the molecular weight of the gas is 44.

• A. $P=0.062$ atm, $T=75$ K
• B. $P=1.062$ atm, $T=75$ K
• C. $P=2.062$ atm, $T=55$ K
• D. $P=3.062$ atm, $T=55$ K

Answer 1

Answer: (A)

$P=0.062$ atm, $T=75$ K

Initial moles, $n=\frac{3.6}{44}$

Final moles, $n^{\prime }=\frac{3.6-0.6}{44}=\frac{3.0}{44}$

Since P and V are constant,

$n_1{T}_1=n_2{T}_2$

$\frac{3.6}{44}\times T=\frac{3.0}{44}\times (T+15)$

$T=75K$

$P=\frac{nRT}{V}=\frac{0.0818\times 75\times 0.0821}{8}=0.062atm$