Question

If 35.0 mL of 0.210 M HCl reacts with excess Mg, how many mL of hydrogen gas are produced at STP?

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)


Is the answer 2.352 STP


converted mols HCl to mols H2 gas:

02.10 M HCl x 1 mol H2/2 mol HCl = 0.105 mol H2


converted mols H2 gas to L:

0.105 mol H2 x 1L/1 mol= 0.105 L H2


multiplied L of H2 to 22.4 STP

0.105L x 22.4 STP= 2.352

Answer 1

No. You don't have 2.10 mols HCl. Did you read my response? mols HCl = M x L = 2.10 x 0.035 = ?
Then convert to mols H2 and from thre to L.