when the total pressure = P gauge + P baro
= 34.2 psi + 14.9 Psi = 49.1 psi
when we convert P = 49.1 from Psi to atm it will be = 3.34 atm
so, by using the ideal gas equation:
PV = nRT
when P is the pressure in atm = 3.34 atm
and V is the volume in L = 4.6 L
n is the number of moles of the gas
R is the gas constant = 0.0821 atm L / mol K
T is the temperature in Kelvin = 30°C + 273 = 303 K
so by substitution in the ideal gas equation:
∴ n = PV / RT
= 3.34 atm * 4.6 L / 0.0821 atm L/mol K * 303 K
= 0.618 moles
∴ there is 0.618 moles of gas