Question

Header & FO 5) Using the data in the table for 0.10 M aqueous species at 25°C, which conjugate base below is the weakest base? Explain your answer for full credit! Acid НОАс 1.8 x 10-5 HC7H502 6.3 x 10-5 HNO2 4.5 x 10-4 HF 6.8 x 10-4 6) The K, for HCN is 4.9 10-10. What is the pH of a 0.068 M aqueous solution of potassium cyanide?

Answer 1

The higher the  K_a, the stronger the acid is, and the weaker its conjugate base is.

So here Ka for HF is highest so it is strongest acid and its conjugate base is weakest.

Order of Ka and acidic strength in increasing order

HOAc < HC7H5O2 < HNO2 < HF

So conjugate base strength will be vice versa of above

Hence conjugate base of HOAc will be strongest base.

And HF conjugate base will be weakest base.

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