Question

What is the mass of aluminum metal that releases 22.4 l of hydrogen gas at stp from hydrochloric acid? __al(s) + __hcl(aq) → __alcl3(aq) + __h2(g) 18.0 g 81.0 g 9.00 g 40.5 g 27.0 g?

Answer 1

The mass  of  Al  metal   that releases 2.4 L  of hydrogen gas at STP  is calculated as below

AT  STP  1 mole  =22.4 l
what about 22.4l =? moles
(22.4 L x 1  mole) /22.4 L= 2mole

write the reacing reaction

2Al+ 6 HCL = 2AlCl3 + 3H2
by use of  mole ratio between  Al to  H2  which is 2 : 3  the   mole Al = 1 x2/3 = 0.667 moles
mass =moles x molar mass
=0.667 mole  x27 g/mol= 18  grams