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1) Calculate the pH of a 2.4 L buffer solution that contains 0.300 M of a weak a

ID: 552692 • Letter: 1

Question

1) Calculate the pH of a 2.4 L buffer solution that contains 0.300 M of a weak acid HA and 0.220 M of its conjugate base, A. The Ka of HA is 5.5x10 2) Assume 0.270 moles of HCl is added to the buffer in number 1. Calculate the pH. Is the buffer still within its effective range? (Convert HA and A concentrations to moles) 3) The ionic compound AB2 has a Ksp 3.16 x 106. Calculate the molar solubility of A B2 4) PbBr2 is made after mixing a solution of 0.003 M Pb(NO3)2 with 0.23 M NaBr. The Kp of PbBr2 is 4.67 x 10. Will precipitate form? (solve for Q and compare with Ksp

Explanation / Answer

Q1

pH = pKa+ log(A-/HA)

pka = -log(5.5*10^-5) = 4.26

pH = 4.26 + log(0.22/0.3)=4.1253

Q2.

mol of HA formed = 0.3*2.4 + 0.27 = 0.99

mol of A- left = 0.22*2.4 - 0.27 = 0.258

pH = pKa+ log(A-/HA)

pH = 4.26 + log(0.258/0.99)

pH = 3.6759