# Problem: A sample of oxygen gas was collected over water. The total pressure in the collection vessel was 744.2 torr, the temperature was 26.0°C and the vessel contained 522 mL of the collected gas. How many moles of oxygen were collected? (At 26.0°C, the vapor pressure of water is 25.2 torr.)(A) 0.231 mol (B) 0.0201 mol(C) 0.151 mol (D) 0.0227 mol (E) 0.0842 mol

###### FREE Expert Solution

We’re being asked to calculate the number of moles of the oxygen gas produced from a reaction that is collected over water.

Oxygen gas is the natural form of oxygen and it is a diatomic molecule (O2).

We’re going to calculate the amount of hydrogen gas in moles using the ideal gas equation.

$\overline{){\mathbf{P}}{\mathbf{V}}{\mathbf{=}}{\mathbf{n}}{\mathbf{R}}{\mathbf{T}}}$

P = pressure, atm
V = volume, L
n = moles, mol
R = gas constant = 0.08206 (L·atm)/(mol·K)
T = temperature, K

Let's first calculate the Partial Pressure of hydrogen gas:

Given:            Total Pressure (Ptotal) = 744.2 mmHg

###### Problem Details

A sample of oxygen gas was collected over water. The total pressure in the collection vessel was 744.2 torr, the temperature was 26.0°C and the vessel contained 522 mL of the collected gas. How many moles of oxygen were collected? (At 26.0°C, the vapor pressure of water is 25.2 torr.)

(A) 0.231 mol

(B) 0.0201 mol

(C) 0.151 mol

(D) 0.0227 mol

(E) 0.0842 mol