Question

A sample of hydrogen gas was collected over water at 36 degree C and 855 mm Hg. The volume of the container was 6.50 L. Calculate the mass of H_2(g) collected. (Vapor pressure of water = 44.6 torr at 36 degree C) a. 0.58 g b.9.38 g c.0.55 g d.4.69 g e. 0.27 g

Answer 1

p_total = p_H_2(g) + P_H_2O (g) 855mm Hg = (P_H_2(g) + 44.6)mm Hg Therefore P_H_2 (g) = (855 - 44.6)mm Hg = 810.4 mm hg = 1.066 atm Now using this p and the values of v and T find n using ideal gas equation n = pv/RT = 8.066atm times 6.50L/0.082 L-atm/mol times 309k = 0.273 moles H_2 Mass of H_2 = moles times molar mass = 0.273moles times 2 g/mol = 0.564g = 0.55g