Ka from pKa

8. Buffer and Isotonic Solution 8.1) Buffer 8.1.1) Determine pKa from Ka

8.1.1.1) Determine pKa from Ka Easy 1


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The pKa of benzoic acid is 4.2. Determine the dissociation constant (Ka) of it.


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lb equals 6.3 × 10−5 kg

    Answer: 6.3 × 10−5 is the Ka of benzoic acid.
    • The antilog of the negative pKa would give us the Ka value.
    • The pKa provided in the question is 4.2
    • Taking negative antilog of the negative of this number we get, antilog(- 4.2) = 6.30 × 10−5
    • Hence, the pKa is 4.2