Chapter 18, Problem 70A

Interpretation Introduction

Interpretation:

The ionization equations and base ionization expressions for the given reaction are to be written.

Concept introduction:

The value of the base ionization constant tells about the state of whether reactants or products are more favored in the reaction.

For a reaction,

   $\text{B}\text{O}\text{H}\rightleftharpoons {\text{B}}^{+}+\text{O}{\text{H}}^{-}$

Base ionization constant is given by:

  $\begin{array}{l}{\text{k}}_{\text{b}}=\frac{\left[{\text{B}}^{+}\right]\times \left[\text{O}{\text{H}}^{-}\right]}{\left[\text{B}\text{O}\text{H}\right]}\end{array}$

  $\begin{array}{c}\text{w}\text{h}\text{e}\text{r}\text{e},\end{array}$

  $\begin{array}{c}\left[{\text{B}}^{+}\right]\text{i}\text{s}\text{c}\text{o}\text{n}\text{c}\text{e}\text{n}\text{t}\text{r}\text{a}\text{t}\text{i}\text{o}\text{n}\text{o}\text{f}{\text{B}}^{+}\end{array}$

  $\begin{array}{c}\left[\text{O}{\text{H}}^{-}\right]\text{i}\text{s}\text{c}\text{o}\text{n}\text{c}\text{e}\text{n}\text{t}\text{r}\text{a}\text{t}\text{i}\text{o}\text{n}\text{o}\text{f}\text{O}{\text{H}}^{-}\end{array}$

  $\begin{array}{c}\left[\text{B}\text{O}\text{H}\right]\text{i}\text{s}\text{c}\text{o}\text{n}\text{c}\text{e}\text{n}\text{t}\text{r}\text{a}\text{t}\text{i}\text{o}\text{n}\text{o}\text{f}\text{B}\text{O}\text{H}\end{array}$

Answer to Problem 70A

Equation:

$\text{N}{\text{H}}_3+{\text{H}}_2\text{O}\rightleftharpoons \text{N}{\text{H}}_4{}^{+}+\text{O}{\text{H}}^{-}$

The base ionization constant is given by:

${\text{k}}_{\text{b}}=\frac{\left[\text{N}{\text{H}}_4{}^{+}\right]\times \left[\text{O}{\text{H}}^{-}\right]}{\left[\text{N}{\text{H}}_3\right]}$

Ammonia is a weak base. Therefore, it is safe to clean the windows using an ammonia solution.

Explanation of Solution

Ammonia is a base, which accepts protons from water. Therefore, the equation is written as:

$\text{N}{\text{H}}_3+{\text{H}}_2\text{O}\rightleftharpoons \text{N}{\text{H}}_4{}^{+}+\text{O}{\text{H}}^{-}$

Using the general expression, k_b is given by:

${\text{k}}_{\text{b}}=\frac{\left[\text{N}{\text{H}}_4{}^{+}\right]\times \left[\text{O}{\text{H}}^{-}\right]}{\left[\text{N}{\text{H}}_3\right]}$

Due to weak acidic character, it is safer to use it in cleaning windows.

Conclusion

Equation:

$\text{N}{\text{H}}_3+{\text{H}}_2\text{O}\rightleftharpoons \text{N}{\text{H}}_4{}^{+}+\text{O}{\text{H}}^{-}$

The base ionization constant is given by:

${\text{k}}_{\text{b}}=\frac{\left[\text{N}{\text{H}}_4{}^{+}\right]\times \left[\text{O}{\text{H}}^{-}\right]}{\left[\text{N}{\text{H}}_3\right]}$

Ammonia is a weak base. Therefore, it is safe to clean the windows using an ammonia solution.