JUST NUMBER 7 AND 8 PLEASE. 6. A solution contains 0.60 mol of NH4Cl and 0.30 mo
ID: 949194 • Letter: J
Question
JUST NUMBER 7 AND 8 PLEASE.
6. A solution contains 0.60 mol of NH4Cl and 0.30 mol of NH3 in 1.5 L. What is the pH if 0.070 mol of HCl is added to this buffer?
7. Instead of adding 0.070 mol of HCl, what would the pH be if 0.070 mol of NaOH is added?
8. Use the two methods to calculate the pH of a buffer that is 1.0 X 10-3 M in CH3COOH and 1.0 X 10-4 M in CH3COONa.
A. Method #1: Henderson-Hasselbalch Equation
B. Method #2: Making No Assumptions – Solving the Quadratic (the % dissociation of this acid is too high, the quadratic formula must be used.)
Explanation / Answer
6. pOH = pkb + log(NH4Cl/NH3)
pkb of NH3 = 4.75
pOH = pkb + log(NH4Cl+HCl/NH3-HCl)
= 4.75+log((0.6+0.07)/(0.3-0.07))
= 5.21
pOH = 5.21
pH = 14-5.21 = 8.79
7. pOH = pkb + log(NH4Cl-NaOH/NH3+NaOH)
= 4.75+log((0.6-0.07)/(0.3+0.07))
= 4.9
pH = 14-4.9 = 9.1
8. a. pH = pka + log(CH3COONa/CH3COOH)
= 4.74 + log((10^(-4))/(10^(-3)))
= 3.74
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