Chapter 9: Q20P (page 209)

Find the pH and concentrations of ${({CH}_{3})}_{3}$ Nand ${({CH}_{3})}_{3} {NH}^{+}$ in a 0.060M solution of trimethylamine.

Short Answer

Expert verified

Concentration of ${({CH}_{3})}_{3}$ Nis 0.058M, Concentration of ${({CH}_{3})}_{3} {NH}^{+}$ is 1.91×10^-3 M and the pH is 11.28

Step by step solution

Introduction

We need to write the chemical equation that describes the ionization of trimethylamine

${({CH}_{3})}_{3} N + H_{2} O ⇌ {({CH}_{3})}_{3} {NH}^{+} + {OH}^{-} [{({CH}_{3})}_{3} N] = 0.06 - x [{({CH}_{3})}_{3} {NH}^{+}] = [{OH}^{-}] = x$

Calculate the value of Kb

We have to calculate value of $K_{b}$ from the value of $K_{w}$ and $K_{a}$ because the product is ${OH}^{-}$

$K_{b} = K_{w} / K_{a} = 6.3 \times 10^{- 5}$

Find out the value of x

Now calculate the value of x by using value of $K_{b}$

$K_{b} = \frac{x^{2}}{0.06 - x} 6.3 \times 10^{- 5} = \frac{x^{2}}{0.06 - x} \Rightarrow x = 1.91 \times 10^{- 3}$

Calculate the pH of solution

Since our product isso first we will have to calculate $pOH$ and then $pH$

$pOH = - logx = - \log (1.91 \times 10^{- 3}) = 2.72 pH = 14 - pOH = 14 - 2.72 = 11.28$

Calculate the concentration of (CH3)3N

$[{({CH}_{3})}_{3} N] = 0.06 - x [{({CH}_{3})}_{3} N] = 0.06 - (1.91 \times 10^{- 3}) [{({CH}_{3})}_{3} N] = 0.058 M$

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Find the pH and concentrations of ${({CH}_{3})}_{3}$ Nand ${({CH}_{3})}_{3} {NH}^{+}$ in a 0.060M solution of trimethylamine.

Short Answer

Step by step solution

Introduction

Calculate the value of Kb

Find out the value of x

Calculate the pH of solution

Calculate the concentration of (CH3)3N

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Find the pH and concentrations of(CH3)3Nand(CH3)3NH+ in a 0.060M solution of trimethylamine.

Short Answer

Step by step solution

Introduction

Calculate the value of Kb

Find out the value of x

Calculate the pH of solution

Calculate the concentration of (CH3)3N

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Nuclear Chemistry

Making Measurements

Kinetics

Physical Chemistry

Chemistry Branches

Chemical Analysis

Study anywhere. Anytime. Across all devices.

Find the pH and concentrations of ${({CH}_{3})}_{3}$ Nand ${({CH}_{3})}_{3} {NH}^{+}$ in a 0.060M solution of trimethylamine.