Question

You have the following reaction: Mg(s) + 2 HCl(aq) + Mg2+(aq) + H2(g) + 2Cl(aq). Answer the following questions with the data given. The hydrogen gas is collected above the aqueous acid solution in an inverted graduated cylinder. Moles of Mg metal: Temperature of gas Atmospheric pressure: 0.0033mol 28.0°C 1.02 atm. 3. What is the pressure of the hydrogen gas in the graduated cylinder?

Answer 1

According to the reaction,

1 unit of Mg gives 1 unit of H₂ gas.

=> 0.0033 mol of Mg will give 0.0033 mol of H₂ gas.

Now, 1 mol of H₂ gas has a volume of 22.4 L.

So, 0.0033 mol of H₂ gas has a volume of 22.4 × 0.0033 L

= 0.07392 L

and, Temperature = 28 ℃ = 301 K

Using the ideal gas equation,

PV = nRT

P = nRT/V

P = 0.0033 mol × 0.0821 L.atm/K/mol × 301 K / 0.07392L

P = (0.0033 × 0.0821 × 301) ÷ 0.07392 atm

P = 0.08155 ÷ 0.07392 atm = 1.10 atm.