We are going to apply the equation of state for ideal gasses: P*V = n*R*T where P is pressure, V is volum, n is mols of gas, T is temperature and R is a constant value of 0.082 (atm*l)/(mol*K)
We know the temperature is 45 ÂşC so in Kelvins will be = 45 + 273.16 = 318.16 K
Then in the equation:
V = n*R*T/P = 1.5 * 0.082 * 318.16 / 2.5 = 15.65 l
So volum of gas is: 15.65 liters