What is limiting reactant in 2Al plus 6HCl equals 2AlCl3 plus 3 H2?

Answer 1

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

The molar ratios are 2:6 :: 2:3

This means that two moles of aluminium will react to completion with exactly six moles of hydrocchloric acid. At completion there will be two moles of aluminium chloride and three moles of hydrogen gas.

So if you had 8 moles of hydrochloric acid and only 2 moles of aluminium, then the aluminium would be the limiting reactant, because from the 8 moles hydrochloric acid you are using only six moles, leaving two moies on hydrochloric acid unreacted.

Conversely, if you had 3 moles of Al and 6 moles HCl , then the HCl would be the limiting reactant. Because the 6 moles of acid would only react with two moles of Al leaving one mole Al unreacted.