What is the pH of a buffer solution that is composed of a weak acid, HA...

What is the pH of a buffer solution that is composed of a weak acid, HA (K_a=8.02×10^–9), and the conjugate base, A^–, after 3.24 mL of 0.089 M HCl solution is added. The initial concentrations of the 142 mL buffer solution are [HA]=0.58 M and [A^–]=0.61 M. Enter your value to two (2) decimal places.

Expert Solution

pH of buffer solutions can be calculated by using Handerson's equation.

pH=pKa+log[salt]/[acid]

HCl is a strong acid.When HCl is added, it reacts with A- and forms:

HCl + A- HA + Cl-

number moles of each substance can be calculated by using the formula: Molarity x volume in L

HCl + A- HA + Cl-

at t=0, 0.0324L x 0.089 M 0.142L x 0.61M 0.58M x 0.142L 0

= 0.000288mol =0.0866mol =0.0824mol 0

after reaction 0 0.0863mol 0.0827mol 0.000288mol

hence pH = -log(8.02×10^–9) + log( 0.0863mol)/(0.0827mol)

= 8.1143

=8.11

queen_honey_blossom answered 2 years ago

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