QUESTION $3$

A steel cylinder contains a mixture of $68$mol$\%$ propane, $21$mol$\%n-$butane and balance is isobutane at $69\mathrm{.}2$atm. Initially, the combined weight of the cylinder and gas is $112\mathrm{.}1kg.$ Over several hours, a portion of the gas is removed from the cylinder. When next the cylinder is examined, the pressure has dropped to $14\mathrm{.}6$atm and the combined mass of the cylinder and remaining gas is $97\mathrm{.}3kg.$ the temperature is maintained at $140C.$ Critical temperature and pressure of each gas is given in Table $1.$

Table $1$ Critical temperature and pressure of each gas component

$\backslash$table$[[$Gas$,\backslash$table$[[$Critical$],[$temperature$,T_c$