Answer:
(a) pH = 1
(b) pH = 7
(c) 60 mL
Explanation:
(a) At the start of the titration, there is only 0.1 M HCl, which is a strong acid, according to the following expression.
HCl → H⁺ + Cl⁻
The concentration of H⁺ is 0.1 M as well and the pH is:
pH = -log [H⁺] = -log 0.1 = 1
(b) The reaction between HCl and NaOH is:
HCl + NaOH → NaCl + H₂O
At the equivalence point, all the HCl and NaOH have reacted. Since NaCl does not contribute to the pH, the pH is 7.
(c) The moles of HCl are:
(0.1 mol/L) × (30.0 × 10⁻³ L) = 3 × 10⁻³ mol
The molar ratio of HCl to NaOH is 1:1, so we also have 3 × 10⁻³ moles of NaOH. The volume of NaOH that contains these moles is:
3 × 10⁻³ mol / (0.1 mol/L) = 0.03 L = 30 mL
The total volume is:
V(HCl) + V(NaOH) = 30 mL + 30 mL = 60 mL
