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.

PV=nRT

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

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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