Small quantities of hydrogen can be prepared by the addition of hydrochloric acid to zinc. a sample of 195 ml of hydrogen was collected over water at 25°c and 753 torr. what mass of hydrogen was collected? (pwater = 24 torr at 25°c)

Let's go over the given information. We have the volume, temperature and pressure. From the ideal gas equation, that's 4 out of 5 knowns. So, we actually don't need Pvap of water anymore. Assuming ideal gas, the solution is as follows:

PV=nRT
Solving for n,
n = PV/RT = (753 torr)(1 atm/760 torr)(195 mL)(1 L/1000 mL)/(0.0821 L·atm/mol·K)(25+273 K)
n = 7.897×10⁻³ mol H₂

The molar mass of H₂ is 2 g/mol.

Mass of H₂ = 7.897×10⁻³ mol * 2 g/mol = 0.016 g H₂

The answer options is d