There is a solution that is 2.2×10 ?2 M in HCN ( K a =4.9×10?10) and 1.0×10 ?2 M

Question

There is a solution that is 2.2×10?2 M in HCN (Ka=4.9×10?10) and 1.0×10?2 M in NaCN.

Part A

Calculate the concentrations of all species present in this solution.

Express your answers in the given order using two significant figures separated by commas.

Homework 49 15.2 to 15.4 Buffers and Common Ions Problem 15.3 There is a solution that is 2.2x10-2 M in HCN (Ka 4.9 x 10-10) and 1.0x10-2 M in NaCN Part A Calculate the concentrations of all species present in this solution Express your answers in the given order using two significant figures separated by commas. ??? H30), CN 1,HCN], [OH l, Na ] Submit Previous Answers Request Answer X Incorrect; Try Again; 5 attempts remaining

Explanation / Answer

[HCN] = 2 x 10^ -2 = 0.02M , [Na+] =[CN-] = 1 x 10^ -2 = 0.01 M ,

pH = pka + log [NaCN] /[HCN] where pka -log Ka = -log ( 4.9 x 10^ -10) = 9.3

pH = 9.3 + log ( 0.01/0.02)

=9

[H3O+] = 10^ -9 M , [OH-] = 10^ -14 / [H3O+] = 10^ -14 / ( 10^ -9) = 10^ -5 M

[H3O+] , [CN-] , [ HCN] , [OH-] , [Na+] = 10^ -9 , 0.01, 0.02 , 10^ -5, 0.01

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