Question

Elemental (metallic) aluminum (Al) is reacted with hydrochloric acid (HCl) to yield aluminum chloride and hydrogen gas. How many grams of metallic aluminum would be required to produce 1 gram of pure hydrogen gas? REMEMBER to balance the reaction and show all steps.

Answer 1

number of mole of H2 = (given mass of H2)/(molar mass of H2)
molar mass of H2 = 2 g/mol
number of mole of H2 = 1/2
= 0.5 mole

reaction taking place
2Al + 6HCl --> 2AlCl3 + 3H2
according to reaction
3 mole of H2 required 2 mole of Al
1 mole of H2 required 2/3 mole of Al
0.5 mole of H2 required (2/3)*0.5 mole of Al
number of mole of Al required = 0.33 mole

molar mass of Al = 27 g/mol
mass of Al required = (number of mole of Al required)*(molar mass of Al)
= (0.33*27) g
= 8.9 g

Answer : 8.9 g