Question

Hydrogen gas can be produced by reacting aluminum with sulfuric acid. how many moles of sulfuric acid are needed to completely react with 15.0 mol of aluminum? 2al(s) + 3h2so4(aq) ® al2(so4)3(aq) + 3h2(g)

Answer 1

The balanced equation for the reaction is as follows
2Al + 3H₂SO₄ --> Al₂(SO₄)₃ + 3H₂
stoichiometry of Al to H₂SO₄ is 2:3
number of Al moles reacted - 15.0 mol 
if 2 mol of Al react with 3 mol of H₂SO₄
then 15.0 mol of Al reacts with - 3/2 x 15.0 mol = 22.5 mol 
22.5 mol of H₂SO₄ is required 

Answer 2

Answer : The number of moles of sulfuric acid needed are, 22.5 moles

Explanation : Given,

Moles of aluminium = 15 moles

The given balanced chemical reaction is,

$2Al(s)+3H_2SO_4(aq)\rightarrow Al_2(SO_4)_3(aq)+3H_2(g)$

By the stoichiometry we can say that, 2 moles of aluminium react with 3 moles of sulfuric acid to give 1 mole of aluminium sulfate and 3 moles of hydrogen gas.

From the balanced chemical reaction, we conclude that

As, 2 moles of aluminium react with 3 moles of sulfuric acid

So, 15 moles of aluminium react with $\frac{3}{2}\times 15=22.5$ moles of sulfuric acid

Therefore, the number of moles of sulfuric acid needed are, 22.5 moles