Certain moles of a weak acid is reacted with 1 ml of 1 N base ( NaOH ) till the equivalence point is reached. It is diluted to 1000 ml . The pH of the solution was found to be 8 . If the same quantity

Question

Certain moles of a weak acid is reacted with 1 ml of 1 N base ( NaOH ) till the equivalence point is reached. It is diluted to 1000 ml . The pH of the solution was found to be 8 . If the same quantity of acid was reacted with NaOH till half the equivalence point was reached. Which of the following is/are correct?

TestHub · Accepted Answer

HA + NaOH → NaA + H₂O Moles: a 1 0 –3 a = 1 0 –3 p H = 7 + 2 1 ​ p K a ​ + 2 1 ​ lo g 1 1 0 − 3 ​ 8 = 7 + 2 1 ​ p K a ​ − 2 3 ​ 1 + 2 3 ​ = 2 p K a ​ ​ = 2 5 ​ p K a ​ = 5 pH at the half-equivalence point is calculated as p H = p K a ​ + lo g ( [ A c i d ] [ S a lt ] ​ ) p H = 5 + lo g ( 1 ) = 5

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