PART A A buffer solution contains 0.358 M ammonium chloride and 0.499 M ammonia
ID: 554368 • Letter: P
Question
PART A
A buffer solution contains 0.358 M ammonium chloride and 0.499 M ammonia.
If 0.0274 moles of perchloric acid are added to 125 mL of this buffer, what is the pH of the resulting solution ?
(Assume that the volume change does not change upon adding perchloric acid)
pH = _______
PART B
A buffer solution contains 0.328 M nitrous acid and 0.481 M sodium nitrite.
If 0.0248 moles of hydrochloric acid are added to 125 mL of this buffer, what is the pH of the resulting solution ?
(Assume that the volume change does not change upon adding hydrochloric acid)
pH = _______
PART C
A buffer solution contains 0.342 M ammonium chloride and 0.337 M ammonia.
If 0.0625 moles of potassium hydroxide are added to 250 mL of this buffer, what is the pH of the resulting solution ?
(Assume that the volume change does not change upon adding potassium hydroxide)
pH = _________
Explanation / Answer
PART A
A buffer solution contains 0.358 M ammonium chloride and 0.499 M ammonia.
moles of NH4Cl = 0.358 x 0.125 = 0.04475
moles of NH3 = 0.499 x 0.125 = 0.0624
moles of HClO4 = 0.0274
pOH = pKb + log [salt + C / base - C]
= 4.74 + log [0.04475 + 0.0274 / 0.06237 - 0.0274]
pOH = 5.05
pH = 8.94
b)
pKa = 3.25
moles of HNO2 = 0.328 x 0.125 = 0.041
moles of NaNO2 = 0.481 x 0.125 = 0.0601
moles of HCl = 0.0248 mol
pH = pKa + log [salt - C / acid + C]
= 3.25 + log [0.0601 - 0.0248 / 0.041 + 0.0248]
pH = 2.98
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