Question

Consider the titration of a 32.0 mL sample of 0.180 M HBr with 0.205 M KOH. Determine each of the following:

-the initial pH
a) 0.74
b) 1.06
c) 1.26
d) 1.48
e) none of these

Answer 1

The initial pH of the titration solution can be calculated using the concentration of CH3CO2H and the equation for its ionization.

Step-by-step explanation:

The initial pH of the titration solution before any amount of the NaOH solution is added can be calculated using the equation for the ionization of CH3CO2H:

CH3CO2H + H2O ⇌ CH3CO2- + H3O+

To find the initial pH, we need to calculate the concentration of H3O+ ions. For CH3CO2H, the equilibrium expression is K₁ = [CH3CO2-][H3O+]/[CH3CO2H]. Since the titration solution is initially only CH3CO2H, we can assume that [CH3CO2-] and [H3O+] are both zero. Therefore, the initial pH is determined by the concentration of CH3CO2H.

For a) 0.00 mL, the concentration of CH3CO2H is 0.180 M. We can calculate the initial pH using the formula pH = -log[H3O+].

pH = -log(0.180) = 0.74