2.5 mL of 25M weak monoacidic base (Kb=1×10−12) at 25oC is titrated with 215M HCl in water at 25oC. The concentration of H+ at equivalence point is (Kw=1×10−14at25oC)
A
3.7×10−13M
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B
3.2×10−7M
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C
3.2×10−2M
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D
2.7×10−2M
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Solution
The correct option is D2.7×10−2M mmol of base =2.5×25=1
mmol of acid required to reach the end point = 1
Volume of acid required to reach the end point = 152mL
Total volume at the end point = 152 + 2.5 = 10 mL
Molarity of salt at the end point = 110=0.10 B+C(1−α)+H2O⇌BOHCα+H+Cα Kh=KwKb=10−2 Kh=10−2=Cα1−α=0.1α1−α ⇒10α2+α−1=0 ⇒α=−1+√1+4020=0.27 ⇒[H+]=Cα=0.1×0.27=0.027M