Question 8.10: Butane, C4H10, is used as a fuel for camping stoves. If you ......

STEP 1   State the given and needed quantities. When three of the quantities (P, V, and T) are known, we use the ideal gas law equation to solve for the unknown quantity, moles (n). Because the pressure is given in mmHg, we will use R in mmHg. The volume given in milliliters (mL) is converted to a volume in liters (L). The temperature is converted from degrees Celsius to kelvins.
Table 1
STEP 2   Rearrange the ideal gas law equation to solve for the needed quantity. By dividing both sides of the ideal gas law equation by RT, we solve for moles, n.
PV=nRT        Ideal gas law equation
\frac{PV}{RT}=\frac{n \cancel{RT}}{\cancel{RT}}
n=\frac{PV}{RT}
STEP 3   Substitute the gas data into the equation, and calculate the needed quantity.
n=\frac{715 \space \cancel{mmHg} \space \space \times \space  0.108 \space \cancel L}{\frac{62.4 \space \cancel L \cdot \cancel{mmHg}}{mole \cdot \cancel K} \space  \times \space 298 \space \cancel K }=0.004 \space 15 \space mole \space (4.15 \space \times \space 10^{-3} \space mole)
Now we can convert the moles of butane to grams using its molar mass of 58.12 g/mole:
0.004 \space 15 \space \cancel{mole \space C_{4}H_{10}} \space \times \space \frac{58.12 \space g \space C_{4}H_{10}}{1 \space \cancel{mole \space C_{4}H_{10}}} =0.241 \space g \space of \space C_{4}H_{10}