Question 5.6: If 3.3 g of a gas at 40°C and 1.15 atm pressure occupies a v...
If 3.3 g of a gas at 40°C and 1.15 atm pressure occupies a volume of 1.00 L, what is the mass of one mole of the gas?
Strategy
This problem is more complicated than previous ones. We are given grams of gas and P, T, and V values and asked to calculate the mass of one mole of the gas (g/mol). We can solve this problem in two steps:
(1) Use the ideal gas law to calculate the number of moles of gas present in the sample. (2) We are given the mass of gas (3.3 grams) and use the ratio grams/mole to determine the mass of one mole of the gas.
Solution
Step 1: Use the P, V, and T measurements and the ideal gas law to calculate the number of moles of gas present in the sample. To use the ideal gas law, we must first convert 40°C to kelvins: 40 + 273 = 313 K.
Step 2: Calculate the mass of one mole of the gas by dividing grams by moles.
Mass of one mole =\frac{3.3 g}{0.0448 mol}=74 g . mol^{-1}