Suggested Response - Q2

*A CO2 recovery balloon holds CO2 at a pressure of 5 kPa g and a temperature of 15 °C. If the balloon volume is 10 m3, what mass of CO2 is held within the balloon? Atmospheric pressure is 100 kPa.

Response:

The problem is suited to being tackled using the universal or ideal gas law:

P V space equals space n R T

Where P is the absolute pressure of the gas; V is the gas volume in m3; n is the number of kmols; R is the universal gas constant, and T is the absolute temperature in Kelvin.

Solving for n, the number of kmols:

n space equals space fraction numerator P V over denominator R T end fraction space equals space fraction numerator left parenthesis 5 space plus space 100 right parenthesis space cross times space 10 cubed space cross times space 10 over denominator 8 comma 314.5 space cross times space left parenthesis 273.15 space plus space 15 right parenthesis end fraction space equals space 0.44 space k m o l

Remember to express the pressure as an absolute pressure and the temperature in Kelvin.

The molecular weight of CO2 is 12 + 2 x 16 = 44 kg/kmol. Consequently, the mass of gas is given by:

m space equals space n space cross times space m o l e c u l a r space w e i g h t space equals space 0.44 space cross times space 44 space equals space 19.4 space k g

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