1. What is the pH of a 5.02×10 -2 M aqueous solution of ammonium bromide , NH 4
ID: 1034872 • Letter: 1
Question
1. What is the pH of a 5.02×10-2 M aqueous solution of ammonium bromide, NH4Br ?
2. The substance formic acid (HCOOH) is a weak acid (Ka = 1.8×10-4).
What is the pH of a 0.276 M aqueous solution of sodium formate, NaHCOO?
3. Which of the following aqueous solutions are good buffer systems? choose all that apply.
0.19 M calcium hydroxide + 0.20 M calcium chloride
0.20 M hydroiodic acid + 0.24 M potassium iodide
0.25 M ammonium nitrate + 0.32 M ammonia
0.13 M hydrofluoric acid + 0.15 M sodium fluoride
0.34 M hypochlorous acid + 0.27 M sodium hypochlorite
4. Which of the following aqueous solutions are good buffer systems? choose all that apply.
0.13 M hydrocyanic acid + 0.18 M potassium cyanide
0.12 M potassium acetate + 0.26 M acetic acid
0.40 M hydrofluoric acid + 0.30 M potassium fluoride
0.25 M ammonium bromide + 0.38 M ammonia
0.21 M perchloric acid + 0.22 M potassium perchlorate
Explanation / Answer
1)
pKb = 4.74
pH = 7 - 1/2 (pKb + log C)
= 7 - 1/2 (4.74 + log 5.02 x 10^-2)
pH = 5.28
2) The substance formic acid (HCOOH) is a weak acid (Ka = 1.8×10-4).
What is the pH of a 0.276 M aqueous solution of sodium formate, NaHCOO?
pKa = 3.74
pH = 7 + 1/2 (pKa + log C)
= 7 + 1/2 (3.74 + log 0.276)
pH = 8.59
3)
0.25 M ammonium nitrate + 0.32 M ammonia
0.13 M hydrofluoric acid + 0.15 M sodium fluoride
0.34 M hypochlorous acid + 0.27 M sodium hypochlorite
4)
0.13 M hydrocyanic acid + 0.18 M potassium cyanide
0.12 M potassium acetate + 0.26 M acetic acid
0.40 M hydrofluoric acid + 0.30 M potassium fluoride
0.25 M ammonium bromide + 0.38 M ammonia
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