Question

If 10.0 grams of magnesium is added to a solution containing 1.00 mole of hydrochloric acid, how many grams of hydrogen gas are produced?

Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq)

Answer 1

Molar mass of Mg = 24.31 g/mol

mass(Mg)= 10.0 g

number of mol of Mg,

n = mass of Mg/molar mass of Mg

=(10.0 g)/(24.31 g/mol)

= 0.4114 mol

moles of HCl = 1.00 g

From reaction,

1 mol of Mg reacts with 2 mol of HCl

so,

0.4114 mol of Mg needs 2* 0.4114 = 0.8228 mol of HCl

we have more than this

So, Mg is limiting reagent

According to reaction,

moles of H2 formed = moles of Mg reacted

= 0.4114 moles

Molar mass of H2 = 2.016 g/mol

mass of H2,

m = number of mol * molar mass

= 0.4114 mol * 2.016 g/mol

= 0.829 g

Answer: 0.829 g