(4)

For describing a particular state of a thermodynamic system, we need state variables such as pressure, temperature and volume. Path variables such as work and heat can only tells us the difference between state variables of two states.

(2)

Here, $P=249$ $\text{kPa}=249\times {10}^3$ $\text{Pa}$

$T=27°\text{C}=27+273=300\text{K}, M=2\times {10}^{-3}\text{kg}$

Equation of state, $PV=nRT$

or     $PM=\rho RT$                                 $[\because n=\frac{m}{M}]$

or     $\rho =\frac{PM}{RT}$

Substituting the values,

$\rho =\frac{(249\times {10}^3)(2\times {10}^{-3})}{8.3\times 300}=0.2$${\text{kg/m}}^3$