Question

During a lab you mix these two solutions a 100ml solution containing 0.40g of NaOH and 200ml of a solution containing 0.73g of HCl. What are the [H+] and the pH in the new solution

Answer 1

moles NaOH = g/molar mass = 0.4/40 = 0.01
mols HCl = g/molar mass = 0.73/36.5 = 0.02
HCl + NaOH ==> H2O + NaCl
1 mol HCl neutralizes 1 mol NaOH so you have 0.01 moles HCl left.
M HCl = moles/L = 0.01/0.300 = 0.0333 M
pH = - log (0.0333) = ?