Question

Calculate the mass of hydrogen formed when 25 grams of aluminum reacts with excess hydrochloric acid.


2Al + 6HCl → Al2Cl6 + 3H2

Answer 1

According to the condition, hydrochloric acid is contained in excess in the reaction mixture. Thus, the amount of hydrogen substance should be calculated using the amount of aluminium substance:

• $ν(Al) = m/M$ = 25(g) / 26.98 (g/mol) = 0.93 mol
• ν (H₂) = $ν (Al) ∙ 3/2$ = 0.93 (mol) ∙ 3/2 = 1.40 mol
• m(H₂) = $ν∙M$ = 1.40 ∙ 2.00 = 2.80 g

Answer: m(H₂)=2.80 g