Question

How much HCl 9in grams) is needed to prepare 546 mL of solution with a pOH of 10.00 at 25?

Answer 1

pOH = 10 means pH = 4 from

pH + pOH = pKw = 14.

pH = 4 = -log(H^+).
Solve for (H^+) = 1E-4 M

You want how many mols? That's 1E-4 mols/L x 0.546 L = ?

Then mol HCl = grams HCl/molar mass HCl.
You know mols and molar mass, solve for grams HCl.