A.)
A 1 liter solution contains 0.343 M
acetic acid and 0.457 M
sodium acetate.
Addition of 0.377 moles of calcium
hydroxide will:
(Assume that the volume does not change upon the addition of
calcium hydroxide.)
Raise the pH slightly
Lower the pH slightly
Raise the pH by several units
Lower the pH by several units
Not change the pH
Exceed the buffer capacity
B.)
A 1 liter solution contains 0.340 M
hydrocyanic acid and 0.453 M
sodium cyanide.
Addition of 0.170 moles of potassium
hydroxide will:
(Assume that the volume does not change upon the addition of
potassium hydroxide.)
Raise the pH slightly
Lower the pH slightly
Raise the pH by several units
Lower the pH by several units
Not change the pH
Exceed the buffer capacity
A)
moles of acetic acid = 0.343
moles of sodium acetate = 0.457
moles of OH- = 0.377 x 2 = 0.754 mol
pH = pKa + log [salt + C / acid - C]
= 4.74 + log [0.457 + 0.754 / 0.343 - 0.754]
here moles of Ca(OH)2 more than acid. so buffer capacity is exceed
Answers :
Raise the pH by several units
Exceed the buffer capacity
B)
Addition of 0.170 moles of potassium
hydroxide will:
moles of HCN = 0.340
moles of NaCN = 0.453
moles of KOH = 0.170
pH = pKa + log [salt + C / acid - C]
= 9.40 + log [0.453 + 0.170 / 0.340 - 0.170]
pH = 9.96
Raise the pH slightly
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