A sample of hydrogen gas was collected over water at 21°C and 685 mmHg.The volume of the container was 7.80 L.Calculate the mass of H₂(g)collected.(Vapor pressure of water = 18.6 mmHg at 21°C.) A)0.283 g B)0.572 g C)0.589 g D)7.14 g E)435 g

Question

Quizplus · Accepted Answer

The total pressure inside the container is the sum of the pressure due to the hydrogen gas and the vapor pressure of water. Therefore, the pressure due to hydrogen gas alone can be calculated as follows:

P(H2) = P(total) - P(H2O vapor)
P(H2) = (685 mmHg - 18.6 mmHg) = 666.4 mmHg

Using the ideal gas law, we can calculate the number of moles of hydrogen gas present:

n(H2) = (P(H2) * V) / (R * T)
n(H2) = ((666.4 mmHg) * (7.80 L)) / ((0.08206 L*atm/mol*K) * (294 K))
n(H2) = 0.339 mol

The mass of hydrogen gas can then be calculated using its molar mass (2.016 g/mol):

mass(H2) = n(H2) * M(H2)
mass(H2) = (0.339 mol) * (2.016 g/mol)
mass(H2) = 0.683 g

Therefore, the mass of hydrogen gas collected is 0.683 g.

A Sample of Hydrogen Gas Was Collected Over Water at 21°C