Question

A student must make a buffer solution with a pH of 2.00. Determine which weak acid is the best option to make a buffer at the specified pH. O propionic acid, K = 1.34 x 10-6, 3.00 M O sodium bisulfate monohydrate, K = 1.20 x 10,3.00 M acetic acid, K, = 1.75 x 10-6, 5.00 M formic acid, K, = 1.77 x 10 , 2.00 M Determine which conjugate base is the best option to make a buffer at the specified pH. sodium formate, HCOONa Osodium propionate, CH,CH,COONa sodium acetate trihydrate, CH,COONa - 3H,0 sodium sulfate decahydrate, Na, So, 10 H,0 The final volume of buffer solution must be 100.00 mL and the final concentration of the weak acid must be 0.100 M. Based on this information, what mass of solid conjugate base should the student weigh out to make the buffer solution with a pH of 2.00? mass=

Answer 1

Your first two options selected are correct!

pKa of sodium bisulfate monohydrate = -log 1.20 × 10^-2 = 1.92

# For weak acid MXV (stock) = MXV (final) → 3.00 MXV = 0.100 M X 100.00 mL = V = 3.33 m2 . So, volume of acid used mil = 13.33 Using Henderson-Hasselbalch equation, [conjugate base] [ weak aud] pH =pka + log + 2.00 = 1.92 + log I conjugale bases 0.100 M = [ conjugate base] = 0.120 M 07 or 0.120 0.120 = mass of sodium sulfate decahydrate Molar mast X OIL =) 0:120 = w 322.2 g X0.14 mol Or mass of conjugate base required =/3.87 g