A chemistry graduate student is given 500 mL of a 1.70 M chloroacetic acid (HCH₂ClCO₂) solution. Chloroacetic acid is a weak acid with Ka = 1.3 × 10⁻³. What mass of KCH₂ClCO₂ should the student dissolve in the HCH₂ClCO₂ solution to turn it into a buffer with pH = 2.80?