Calculate the mass of Mg needed to produce ~40 mL of H2. how do I do this?

Answer 1

write a balanced chemical equation.

Mg+2HCl>>MgCl2 + H2

so for each mole of H2, one mole of Mg is required.

Answer 2

how do i figure out the moles of H2? Do I convert the mL to L and then divide that by the mass of H2?