A 40.00 mL aqueous solution of 0.100 M potassium cyanide is titrated with 0.150 M HBr....

A 40.00 mL aqueous solution of 0.100 M potassium cyanide is titrated with 0.150 M HBr. What is the pH of the solution at the equivalence point?
Correct Answer: 2.99
-I just want to know how its done. Thank you.

Expert Solution

At equivalence point :

millimoles of CN- = millmoles of HBr

40 x 0.1 = 0.150 x V

V = 26.67 mL

CN- (aq) + HBr ----------------> HCN + Br-

4 4 0

0 0 4

here HCN is formed .

concentration of [HCN] = 4 / (40 + 26.67) = 0.06 M

pKa = 9.21

pH = 1/2 (pKa - log C)

= 1/2 (9.21 - log 0.06)

pH = 5.22

NOte : check your answer once. it is wrong. correct answer 5.22

queen_honey_blossom answered 2 years ago

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A 40.00 mL aqueous solution of 0.100 M potassium cyanide is titrated with 0.150 M HBr....

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