Using the Kb for NH3 calculate the Ka for the NH4 ion Compar

Using the Kb for NH₃, calculate the Ka for the NH₄⁺ ion. Compare this value with that calculated from your measured pH.

Compound

Kb Value Given

Calculated Ka

Measured pH

NH₃

1.8×10^-5

1.74×10^-10

5.38

Solution

NH4+ + H2O ----------- NH4OH + H+

Ka= [NH4OH][H+]/[NH4+]

Kb= 1.8x10^-5

Ka xKb= Kw                Kw = ionic product of water= 1.0x10^-14

Ka= Kw/Kb = 1.0x10^-14/1.8x10^-5 = 5.56 x10^-10.

Ka= 5.56x10^-10.

Ka value is caluclated from given kb value is greater than the Ka valude is calculated from given PH value.