A gas sample contains 4.0 g of CH₄ and 2.0 g of He. What is the volume of the sample at STP?

Question

Quizplus · Accepted Answer

1. Calculate the number of moles of CH₄: 4.0 g / 112.5 g/mol = 0.0356 mol 2. Calculate the number of moles of He: 2.0 g / 4.00 g/mol = 0.500 mol 3. Add the number of moles of each gas: 0.0356 mol + 0.500 mol = 0.536 mol 4. Use the combined gas law to calculate the volume at STP: PV = nRT P = 1 atm V = ? n = 0.536 mol R = 0.0821 L•atm/mol•K (universal gas constant) T = 273 K V = (nRT)/P = (0.536 mol)(0.0821 L•atm/mol•K)(273 K) / (1 atm) = 16.7 L ≈ 17 L (rounded to two significant figures) Therefore, the answer is choice C.

A Gas Sample Contains 4