Question

11. Which has the greatest buffering capacity? Explain your answer. (3 points) A) 0.821 MHF and 0.909 M NaF C) 0.121 M HF and 0.667 M NaF B) 0.100 M HF and 0.217 M NaF D) 0.821 M HF and 0.217 M NaF E) They are all buffer solutions and would all have the same capacity 12. Calculate the pH of a solution prepared by dissolving 0.423 mol of formic acid (HCOOH) and 0.325 mol of sodium formate (HCOONa) in water sufficient to yield 1.50 L of solution. The K, of formic acid is 1.77 10 (6 points)

Answer 1

Answer is as follows

11. It is a cule of thumb that suffill works best when the amount on concentration of an acid and its conjugate base is owuguly equal. This is so because of Hendesen Hasselbalcho equation asi - pH = pkat log [ Conjugate Base] . (acid ] pH = pka + log Calef] [HF) So when the [nat ] = CHF Ig minimum change 1 of pH occurs inhen can cacia on base added. Out of the option 0.821 MHF andle 0.909M Naf chas the closest concentration and hence us he . most effective Answer 4 U Hendersen Hasselbalch equation state 1. ÞH= pka + log [Hoo Na] - © . [HCoor] Concentration - No. of moles (Molarity) Volume of solution Cincitries) ... [ncooh] = 0.423 mol -0.282 M 150L [HCOONa ] = 0.325 mol = 0.216 M 1-50 L þ Ha = -log Ka = -log. (1.77% 104) bka = 3.75% ... from ① (6.216 ) pH = 3.152+ log oikoa) = 3.752 -0.116 = 3.631 pH