From the coefficients of the equation, we know that for every 2 moles of Al consumed, 6 moles of HCl are consumed.
This means 6(2/2)=6 moles of HCl are needed.
Since there are [tex]6.022 \times 10^{23}[/tex] molecules in 1 mole of a substance, there are :
[tex]6(6.022 \times 10^{23}}=\boxed{4 \times 10^{24} \text{ (to 1 sf)}}[/tex]
