Asked Jul 27, 2019

Determine the pH of a solution that is 0.20 M in NHand 0.30 M NH4Cl


Expert Answer

Step 1

The mixture of NH3 with NH4Cl is a buffer solution as it is a mixture of weak base (NH3) with its conjugated acid (NH4+) from NH4Cl.

NH4Cl is a soluble ionic compound, therefore when it is added to water it undergoes the below reaction:


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H2ONHA aq) Cl (aq) NHCl 4 S 4 340

Step 2

The given solution contains 0.20 M NH3 and 0.30 M NH4+. Since it is a solution of a weak base and its conjugate acid, and so is a buffer solution and to calculate the pH of buffer solution, Henderson equation must be used:


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pH - pКа + log Base] [аcid] [NH pH 3 рКa + log [NH+ 4

Step 3

Calculate  Ka and pKa from  Kb value of NH3.

Kb valu...


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KW Ka 1.0 10 56 x 10-10 Substitute the values: Ka 1.8 x 105 pKa -log [Ka pKa -log [5.6 x 10-10] pK 2 a


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