Chemistry Question

Question

When aluminum is placed in concentrated hydrochloric acid, hydrogen gas is produced.

$2Al(s)+6HCl(aq)⟶2AlCl3(aq)+3H2(g)$

What volume of $H_{2}^{} (g)$ is produced when $7.90$ g $Al (s)$ reacts at STP?

volume of H2(g) = ____L

JACQUES D. · Accepted Answer

Stoichiometry problem that you want to go from g of Al to moles of Al, to moles of H₂to liters of H₂ at STP. Easiest method is factor labeling:

Start with what you know (quantity) and cancel units until you get what you want:

7.90 g Al*(1 mole/ 26.98 g Al)*(3 mole H₂/2 moles Al)(22.4 liters/mole) = 9.84 liters H₂

where g/mol Al is from PT, 3H₂/2Al is from rxn statement, and 22.4 l/mole is true for IGs at STP.

Hope that helps.

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