Question

How many grams of H2(g) can theoretically be produced from a 5-g sample of magnesium metal and excess HCl(aq)?

Answer 1

Molar mass of Mg = 24.31 g/mol

mass of Mg = 5 g

mol of Mg = (mass)/(molar mass)

= 5/24.31

= 0.2057 mol

we have the Balanced chemical equation as:

Mg + 2 HCl —> MgCl2 + H2

From balanced chemical reaction, we see that

when 1 mol of Mg reacts, 1 mol of H2 is formed

mol of H2 formed = moles of Mg

= 0.2057 mol

Molar mass of H2 = 2.016 g/mol

mass of H2 = number of mol * molar mass

= 0.2057*2.016

= 0.415 g

Answer: 0.415 g