You are titrating 0.200 L of a 0.400M monoprotic weak acid with a strong base that is 0.800 M.
Ka= 4.8x10^-6
a) At first, there is 0.200 L of 0.400M acid and no strong base. What is the pH?
b) After 35.0 mL of 0.800 M strong base is added, what is the pH?
c) How many mL of 0.800 M strong base must be added to reach the half equivalence point?
d) What is the pH of the equivalence point?
f) What is the pH after 102mL of 0.800 M strong base is added?
g) If the strong base were NaOH, how many moles of NaOH is present at the equivialence point, half-equivalences point and buffer region?
pka of acid = -log(4.8*10^(-6)) =5.32
No of mol of acid = 0.2*0.4 = 0.08 mol
a) pH = 1/2(pka-logC)
= 1/2(5.32-log0.08)
= 3.2
b) No of mol of base = 35/1000*0.8 = 0.028 mol
pH = pka + log(salt/base)
= 5.32 + log(0.028/(0.08-0.028))
= 5.05
c) at half equivalent No of mol of base = 1/2*0.08 = 0.04 mol
volume of base = 0.04/0.8 = 0.05 L
= 50 ml
e) at equivalencepoint
concentration of salt = 0.08/(0.2+0.1) = 0.27 M
pH = 7+1/2(pka+logC)
= 7+1/2(5.32+0.27)
= 9.8
f) No of mol of base = 0.102*0.8 = 0.0816 mol
no of mol of acid = 0.08 mol
excess base = 0.0816-0.08 = 0.0016 mol
concentration of base = 0.0016/(0.2+0.102) = 0.0053 M
POH = -LOG0.0053 = 2.27
Ph = 14-2.27 = 11.73
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