Aballoon is filled to a volume of 5.10l at a temperature of 27.1ºc. if the pressure in the balloon is measured to be 2.20 atm, how many moles of gas are contained inside the balloon?

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

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