Question

Aluminum reacts with excess hydrochloric acid to form aqueous aluminum chloride and 49.6 mL of hydrogen gas over water at 27°C and 751 mmHg. How many grams of aluminum reacted? The partial pressure of water at 27°C is 26.8 mmHg.

Answer 1

2 Al (s)   +   6 HCl (aq)   --------------> 2 AlCl3 + 3 H2 (g)

volume of H2 = 49.6 mL

temperature = 27 oC = 300 K

pressure = 751 - 26.8 = 724.2 mmHg = 0.953 atm

P V = n R T

0.953 x 0.0496 = n x 0.0821 x 300

n = 1.919 x 10^-3

moles of H2 = 1.919 x 10^-3

1 mol Al   -----------> 3 mol H2

   ??         -----------> 1.919 x 10^-3 mol H2

moles of Al = 6.396 x 10^-4 mol

mass of Aluminum reacted = 0.0173 g