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What is the initial pH of a titration of 25.0 mL of 0.126 M NH3 with...

What is the initial pH of a titration of 25.0 mL of 0.126 M NH3 with 0.287 M HCl? Kb = 1.8 x 10-5   SHOW WORK

a. 11.18

b. 7.00

c. 2.82

d. 1.04

e. 0.54

Solutions

Expert Solution

          NH3      +   H2O --------------> NH4+ + OH-

   0.126 M                                     0          0

               0.126-x                                      x         x

      Kb = [NH4+] [OH-] /[NH3]

1.8 x 10-5 = x.x / 0.126-x  

Since x is very small, 0.126 -x = 0.126

   Then,

1.8 x 10-5 = x.x / 0.126

   x = 0.0015 M

[OH-] = 0.0015 M

pOH = - log [OH-] = - log (0.0015) = 2.82

Hence,

pH = 14 -pOH= 14- 2.82= 11.18

Therefore,

Initial pH = 11.18

--------------------------------------

Ans = a

queen_honey_blossom answered 1 year ago
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