Calculate the pH of each of the following solutions. a. 0.10 M CH 3 NH 3 Cl b. 0.050 M NaCN

Interpretation: The pH value for each of the given solutions to be calculated.

Concept introduction: The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

The pOH of a solution is calculated by the formula, pOH=−log[OH−]

The sum, pH+pOH=14

At equilibrium, the equilibrium constant expression is expressed by the formula,

Ka=Concentration of productsConcentration of reactants

The value of Kw is calculated by the formula,

Kw=Ka⋅Kb

To determine: The pH value for each of the given solution of 0.10 M CH3NH3Cl .

Explanation

The equilibrium constant expression for the given reaction is, Ka=[CH3NH2][H+][CH3NH3+]

CH3NH3+ is a stronger acid than H2O .

The dominant equilibrium reaction is,

CH3NH3+(aq)⇌CH3NH2(aq)+H+(aq)

At equilibrium, the equilibrium constant expression is expressed by the formula,

Ka=Concentration of productsConcentration of reactants

Where,

• Ka is the acid dissociation constant.

The equilibrium constant expression for the given reaction is,

Ka=[CH3NH2][H+][CH3NH3+] (1)

The Ka value is 2.28×10-11 M_ .

The value, Kw=Ka⋅Kb

The value of Kb for methyl amine is 4.38×10−4 .

The value of Ka is calculated by the formula,

Ka=KwKb

Substitute the value of Kb in the above expression.

Ka=1.0×10−144.38×10−4=2.28×10-11_

The [H+] is 1.50×10-6 M_ .

The change in concentration of CH3NH3+ is assumed to be x .

The liquid components do not affect the value of the rate constant.

The ICE table for the stated reaction is,

CH3NH3+(aq)⇌CH3NH2(aq)+H+(aq)Inititial concentration0

Interpretation: The pH value for each of the given solutions to be calculated.

Concept introduction: The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

The pOH of a solution is calculated by the formula, pOH=−log[OH−]

The sum, pH+pOH=14

At equilibrium, the equilibrium constant expression is expressed by the formula,

Ka=Concentration of productsConcentration of reactants

The value of Kw is calculated by the formula,

Kw=Ka⋅Kb

To determine: The pH value for each of the given solution of 0.050 M NaCN .