to find the number of moles of gas we can use the ideal gas law equation
PV = nRT
where P - pressure - 3.4 atm
V - 0.500 L
n - number of moles
R - universal gas constant - 0.0821 L.atm/mol.K
T - temperature in kelvin - 45 °C + 273 = 318 K
substituting these values in the equation
3.4 atm x 0.500 L = n x 0.0821 L.atm/mol.K x 318 K
n = 0.065 mol
0.065 mol of gas is present
