A sample of hydrogen (H2) gas is collected over water at 35C and 745mm. the volume of the gas collected is 72.0ml. How many moles of H2 gas have been collected?

Question

A sample of hydrogen (H2) gas is collected over water at 35C and 745mm. the volume of the gas collected is 72.0ml. How many moles of H2 gas have been collected?

Answer 1

From PV = nRT you can solve for n (moles)

P = 745 mm Hg x 1 atm/760 mm Hg = 0.980 atm

V = 72 ml = 0.072 L

n = ?

R = gas constant = 0.0821 L-atm/K-mole

T = temperature in ºK = 35ºC + 273 = 308ºK

 

Solving for moles (n):

n = PV/RT

Substitute the values and calculate moles of gas