we can find the number of moles in the balloon using the ideal gas law equation
PV = nrT
where
P - pressure - 2.20 atm
V - volume - 5.10 L
n - number of moles
r - universal gas constant - 0.08206 LatmK⁻¹mol⁻¹
T - temperature in Kelvin - 27.1 °C + 273 = 300.1 K
substituting the values in the equation
2.20 atm x 5.10 L = n x 0.08206 LatmK⁻¹mol⁻¹ x 300.1 K
n = 0.456 mol
number of moles of gas is 0.456 mol
