Chapter 18.4, Problem 46PP

Interpretation Introduction

Interpretation:

Volume of given ammonium hydroxide solution is to be calculated when it is neutralized by acid.

Concept introduction:

Molarity is number of moles of solute present per liter of solution.

When acid and base are mixed, they neutralize each other. So their molar concentrations can be calculated by applying mole concept.

Answer to Problem 46PP

Volume of ammonium hydroxide is $15mL$

Explanation of Solution

Given data:

$\begin{array}{l}{V}_{H_{3}P{O}_4}=25mL\\ Molarityof{H}_{3}P{O}_4=0.1\text{}M\\ MolarityofNaOH=0.5\text{}M\end{array}$

$\begin{array}{c}{n}_{H_{3}P{O}_4}=Molarity\times volumeinliters\\ =0.1\times \frac{25}{1000}\\ =2.5\times {10}^{-3}mol\end{array}$

When phosphoric acid reacts with ammonium hydroxide reaction is given by:

$H_{3}P{O}_4+3NaOH\to N{a}_{3}P{O}_4+3H_{2}O$

Thus one mol acid reacts with three mol base.

This impies,

$\begin{array}{c}{n}_{NaOH}=3\times 2.5\times {10}^{-3}\\ =7.5\times {10}^{-3}mol\end{array}$

$\begin{array}{c}VolumeofNaOHsolution=\frac{7.5\times {10}^{-3}mol}{0.5}\\ =15\times {10}^{-3}L\\ =15mL\end{array}$

Conclusion

$VolumeofNaOH=15mL$