STP chemisty question?

Question

Aluminum metal shavings (10.0g) are placed in 100. mL of 6.00 M of hydrochloric acid. What is the maximum volume of hydrogen, measured at STP, which can be produced?

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

Answer 1

Find the moles of Al:

n = m/Ar = 10/27 = 0.37 mol (approx) where Ar = 27 is the relative atomic mass of Al.

Find the moles of HCl:

n = C*V = 6*0.1 = 0.6 mol HCl

According to the balanced chem. equation:

2Al + 6HCl --> 2AlCl3 + 3H2

1 mol of Al reacts with 3 mol of HCl, so
0.37 mol of Al reacts with 3*0.37 = 1.11 mol of HCl

So HCl is the limiting reactant and because:

6 mol of HCl produces 3 mol H2
0.6 mol of HCl produces 0.3 mol H2

This quantity - 0.3 mol of H2 - at STP occupies:

V = n*Vm = 0.3*22.4 = 6.72 L, where Vm = 22.4 L/mol is the molar volume in STP.