A- [tex] 12 \; cm^3 [/tex]
From coefficients in the equation, for each mole of propane combusted, three moles of carbon dioxide molecules are produced. Thus
[tex] n(CO_2) = 3 \; n(C_3H_8) [/tex]
The question implied that the temperature and pressure on both carbon dioxide [tex] CO_2 [/tex] and propane are those under room conditions- so these values are supposed to be interchangeable; thus by the ideal gas equation
[tex] V(CO_2) = \frac{P \cdot V}{n(CO_2) \cdot R \cdot T} = \frac{P \cdot V}{3 \; n(C_3H_8) \cdot R \cdot T} = 3 \; V(C_3H_8) = 3 \cdot 4 \; cm^3 = 12 \; cm^3 [/tex]
