if an acetic acid/sodium acetate buffer solution is prepared from 100ml of 0.10M
ID: 842496 • Letter: I
Question
if an acetic acid/sodium acetate buffer solution is prepared from 100ml of 0.10M acetic acid, what volume of 0.10M sodium acetate must be added to have a pH of 4.00
b) when mixed in appropraite amounts, which of the following mixtures can produce an effective buffer solution
- 0.20M HCN and 0.10M KCN , or 0.20M HCL and 0.10M KOH, or 0.20M CH3CO2H and 0.10 M HCO2H, or 0.10 HCL and 0.010 KCL , or none of the above
c) what mass of solid NaCH3CO2 should be added to 1.0L of 0.5M CH3CO2H to make buffer with a pH of 7.21. pKa of CH3CO2H=7.21
Explanation / Answer
a.
pH=pKa+ log(base/acid)
no of moles of aceticacid = 0.1*100/1000 = 0.01 mol
let no of moles of Sodium acetate = x
generally pKa of acetic acid = 4.75
4= 4.75+ log(x/0.01)
-0.75 = log(x/0.01)
x=0.00178 mol
volume of Sodium acetate = n/M = 0.00178/0.1 =0.0178 lit
= 17.8 ml
b. 0.20M HCN and 0.10M KCN
c.
pH=pKa+ log(base/acid)
let concentration of Sodium acetate = x
generally pKa of acetic acid = 4.75
7.21= 7.21+ log(x/0.5)
0 = log(x/0.5)
x=0.5
mass of Sodium acetate = 0.5*82.03 = 41.015 grams
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