Chapter 6, Problem 6A.24E

Interpretation Introduction

Interpretation:

Molar concentration of ${\text{KNH}}_{\text{2}}$ and also the molar concentration of ${\text{K}}^{\text{+}}$, ${\text{NH}}_{\text{2}}{}^{-}$ and ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ has to be calculated if $\text{0}\text{.40}\text{g}$ of ${\text{KNH}}_{\text{2}}$ is present in $\text{0}\text{.450}\text{L}$ of aqueous solution.

Concept Introduction:

Molarity of a solution is defined as the number of moles of solute dissolved in per liter of a solution.  This can be expressed as shown below;

    $\text{Molarity}=\frac{\text{number}\text{of}\text{moles}}{\text{Volume}\text{of}\text{solution}}$

Autopyrolysis is a reaction in which proton is transfer from one molecule to another molecule of same kind.  Autopyrolysis constant can be expressed by the equation shown below;

    $K_W=[{\text{H}}_{\text{3}}{\text{O}}^{+}][{\text{OH}}^{-}]$

For pure water the value of autopyrolysis constant is equal to $1.0\times {10}^{-14}$ at $\text{25°C}$.  Unit of autopyrolysis constant is ${\text{mol}}^{\text{2}}\cdot {\text{L}}^{-2}$.  This is because, the unit for concentration of hydroxide ion and hydronium ion is $\text{mol}\cdot {\text{L}}^{-1}$.