If sufficient acid is used to react completely with 21.0 grams of Mg

Mg(s) + 2 HCl(aq) + MgCl2(aq) + H2(g)

what volume of hydrogen at STP would be
produced?

1. 9.68 liters
2. 10.60 liters
3. 4.84 liters
4. 19.37 liters
5. 22.40 liters

Solution,

Mass of Mg - 21gm

molar mass of Mg - 24gm

moles = Given mass/ Molar mass

moles = 21/24 = 0.875

1 mole of Mg produce 1 mole of H2 gas

so 0.875 mole of Mg will produce 0.875 moles of H2 gas

One mole of H2 gas = 22.4 litre

0.875 mole of H2 gas = 0.875×22.4

0.875 mole of H2 gas = 19.60 litre

So the nearest ANSWER is Option four 19.37 litre.

i just learnt this recently but i need to look through my notes again