What volume of hydrogen gas, at 25.0 ∘C and 689.3 torr, will form when 749 mL of 4.09 M HCl reacts with excess Mg?

The equation for this reaction is:

Mg + 2HCl = MgCl₂ + H₂

The moles of Hydrogen produced are half that of HCl

Moles of HCl present:

moles = concentration x volume

= 4.09 x 0.749

= 3.06

Moles of Hydrogen produced = 3.06/2 = 1.53

Now, we apply the ideal gas equation:

PV = nRT

The pressure in Pascals = 689.3 x 133.3

= 92000 Pa

V = (1.53 x 8.314 x (25 + 273)) / 92000

V = 0.04 m³