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

Idont know. if you want an answer you need to give us some context dude.