For which type of titration will the pH be basic at the equivalence point? Stron
ID: 945776 • Letter: F
Question
For which type of titration will the pH be basic at the equivalence point? Strong acid vs. strong base. Strong acid vs. weak base. Weak acid vs. strong base. All of the above. None of the above. 50.00 mL of 0.10 M HNO_2 (nitrous acid, K_a = 4.5 10^-4) is titrated with a 0.10 M KOH solution. After 25.00 mL of the KOI solution is added, the pH in the titration flask will be 2.17 3.35 2.41 1.48 7.00 A titration of an acid and base to the equivalence point results in a noticeably acidic solution. It is likely this titration involves a strong acid and a weak base.Explanation / Answer
22. When titration is between a weak acid and strong base, the pH will be basic at equivalence point.
23.
Moles of HNO2 in 50ml of 0.1M =0.1*50/1000=0.005 moles
Moles of KOH in 0.1M and 25ml =0.1*25/1000 =0.0025 moles
HNO2 + KOH--à H2O+KNO2
1 mole of KOH consumes 1 mole of HNO2
So moles of HNO2 remaining =0.005-0.0025=0.0025 moles
Volume after mixing = 50+25= 75ml =75/1000 =0.075L
Concentration of HNO2= 0.00025/0.075=0.033
Moles of conjugate base =0.0025/0.075=0.033
From pH= pKa+ log [conjugate base/ acid] =pKa+log[0.033/0.033]
Given Ka= 4.5/10^5, pKa= -log (4.5/10^4)=3.35
pH= 3.46+0 =3.35
24. A titration of a strong acid and a weak base to the equivalence point results in a notcieably acidic solution.