1: Calculate pH of a weak acid/conjugate base buffer solution. Close Problem Cal
ID: 705545 • Letter: 1
Question
1:
Calculate pH of a weak acid/conjugate base buffer solution.
Close Problem
Calculate the pH of 770. mL of a 8.42×10-2-M solution of nitrous acid before and after the addition of 0.124 mol of potassium nitrite.
pH before addition =
pH after addition =
1.1:
Calculate pH of a weak base/conjugate acid buffer solution.
A 0.323-M aqueous solution of NH3 (ammonia) has a pH of 11.4. Calculate the pH of a buffer solution that is 0.323 M in NH3 and 0.115 M inNH4+.
pH =
1.2:
Use the Henderson–Hasselbalch equation to calculate pH of a buffer solution.
Using the Henderson-Hasselbalch equation, calculate the pH of a buffer solution that is 0.407 M in HCO3- and 0.231 M in CO32-.
pH =
1.3:
Calculate buffer pH after adding strong acid or strong base.
Determine the pH change when 0.100 mol HCl is added to 1.00 L of a buffer solution that is 0.410 M in HCN and 0.337 M in CN-.
pH after addition ? pH before addition = pH change =
Explanation / Answer
1) before
pH = 1/2(pka-logC)
pka of HNO2 = 3.15
C = concentration of HNO2 = 0.0842 M
pH = 1/2(3.15-log0.0842) = 2.112
after addition of KOH
pH = pka + log(KNO2/HNO2)
no of mol of KNO2 = 0.124 mol
no of mol of HNO2 = 0.77*0.0842 = 0.065 mol
pH = 3.15+log(0.124/0.065) = 3.43
1.1) CONCENTRATION of NH3 taKen(base) = 0.323 M
CONCENTRATION of NH4+ added(acid) = 0.115 M
pH of basic buffer = 14-(pkb+log(acid/base))
pkb of NH3 = -lohKb = -log(1.8*10^-5) = 4.74
pH = 14-(4.74+log(0.115/0.323)) = 9.7
1.2)
pH = pka2 + log(CO32-/HCO3-)
pka2 of H2CO3 = 10.33
[co32-] = 0.231 M
[HCO3-] = 0.407 M
pH = 10.33+log(0.231/0.407) = 10.08
1.3)
pH = pka + log(CN-/HCN)
pka of HCN = 9.31
pH = 9.31+log(0.337/0.41) = 9.225
after addition of HCl
pH = pka + log((CN- - HCl)/(HCN+Hcl))
= 9.31+log((0.337-0.1)/(0.41+0.1))
= 8.98
change in pH = 9.225-8.98 = 0.245
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