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

2Al(s)+6HCl(aq) yeilds 2AlCl3(aq)+3H2(g

What volume of H2(g) is produced when 6.50 g of Al(s) reacts at STP?

## Answer

the coefficients of this equation

2 Al (s) + 6 HCl (aq) -------> 2 AlCl3 (aq) + 3 H2 (g)

are in mole ratios. so all you need to do is

(1).. convert g Al to moles Al

(2).. use the coefficients to convert moles Al to moles H2

(3).. since this is at STP.. use 22.41L = 1 mole @STP to convert moles H2 to L H2

and of course you should be using dimensional analysis

6.5g Al x (1 mole Al / 26.98g Al) x (3 moles H2 / 2 moles Al) x (22.41 L H2 / mole [email protected]) = 8.104L H2

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