Tugas Kuliah Asam Basa Part II

  1. Deuteroammonia, ND3, is a weak base with a pKb of 4.96 at 25oC. What is the pH of a 0.20 M solution of this compound?

Answer :::

pKb     = 4,96

pKb     = 5 – 0,04

Kb       = 5 – log 1,096

Kb       = 1,906 x 10-5

 

[ OH ]      =                                         pOH    = – log [ OH ]

=                                    = – log 0,468 x 10-3

=                                             = 3 – log 0,468

= 0,468 x 10-3

 

pH       =  14 – pOH

=  14 – (3 – log 0,468)

=  11 + log 0,468

=  10,6703

 

 2. A solution of acetic acid has a pH of 2.54. What is the concentration of acetic acid in this solution ?

Answer :::

pH       =  – log [ H+ ]                                       [ H+ ]   =

2,54     = – log [ H+ ]                            2,884 x 10-3       = 

[ H+ ]   =  3 – 0,04                               (2,884 x 10-3)2 =  2 x 10-5 .  Ma

=  3 – log 2,884                                   Ma       =

=  2,884 x 10-3                                                     =  4,1585 x 10-1

 

Jadi konsentrasi  adalah 4,1585 x 10-1 M

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