Question

What minimum amount of 1.55 M \rm HCl is necessary to produce 26.5 L of \rm H_2 at STP?

Answer 1

mols H2 needed = 26.5L/22.4L = ?
Convert mols H2 to mols HCl. Then
MHCl = mols HCl/L HCl. You know M and mols solve for L HCl.