# An empty LPG cylinder weighs

Question:

An empty LPG cylinder weighs $14.8 \mathrm{~kg}$. When full, it weighs $29.0 \mathrm{~kg}$ and shows a pressure of $3.47$ $\mathrm{atm}$. In the course of use at ambient temperature, the mass of the cylinder is reduced to $23.0 \mathrm{~kg}$. The final pressure inside of the cylinder is atm. (Nearest integer)

(Assume LPG of be an ideal gas)

Solution:

Initial mass of gas $=29-14.8=14.2 \mathrm{Kg}$

mass of gas used $=29-23=6 \mathrm{Kg}$

gas left $=14.2-6=8.2 \mathrm{Kg}$

(1) $3.47 \times \mathrm{V}=\left(\frac{14.2 \times 10^{3}}{\mathrm{M}}\right) \times \mathrm{R} \times \mathrm{T}$

(2) $\mathrm{p} \times \mathrm{V}=\left(\frac{8.2 \times 10^{3}}{\mathrm{M}}\right) \times \mathrm{R} \times \mathrm{T}$

Divide :

$\frac{(1)}{(2)} \Rightarrow \frac{3.47}{\mathrm{P}}=\frac{14.2}{8.2}$

$P=2.003$