What is the volume in (L) of hydrogen gas obtained if 0.15 g H2 are produced in the reaction of magnesium and HCl? Assume the temperature is 25’C and the pressure of the H2 gas is 0.972 atm.

Answer 1

Use the ideal gas law PV = nRT

P = pressure in atm = 0.972 atm

V = volume in liters = ?

n = mols of gas = 0.15 g H₂ x 1 mol H₂ / 2 g = 0.075 mols H₂

R = gas constant = 0.0821 Latm/Kmol

T = temperature in Kelvin = 25ºC +273 = 298K

Solve for V (volume):

V = nRT / P = (0.075)(0.0821)(298) / 0.972

V = 1.9 liters (2 sig. figs.)