Chapter 15, Problem 10STP

Interpretation Introduction

Interpretation:

The compound with largest equivalent weight is to be chosen.

Concept introduction:

Equivalent weight of an acid is calculated by dividing the molecular weight of compound by basicity of the acid.

Basicity of acid is the number of hydrogen ion it can replace in aqueous medium.

Answer to Problem 10STP

D

Explanation of Solution

  $\begin{array}{c}\text{Molecular weight of HCl=1 g/mol+35}\text{.5 g/mol }\end{array}$

               $\begin{array}{c}\text{=36}\text{.5 g/mol}\end{array}$

Basicity of $\mathrm{H}\mathrm{C}\mathrm{l}$ =1

Equivalent weight of HCl will be:

  $\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}=\frac{36.5}{1}$

Molecular weight of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ will be:

  $\begin{array}{c}\mathrm{M}=\left(2+32+64\right)\text{ g/mol}\end{array}$

   $\begin{array}{c}=98\text{ g/mol}\end{array}$

Basicity of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ =2

  $\begin{array}{c}\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{o}\mathrm{f}{\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4=\frac{98}{2}\end{array}$

                $\begin{array}{c}=49\end{array}$

Thus,

  $\begin{array}{r}\mathrm{M}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{r}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{o}\mathrm{f}{\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_4=3+31+64\end{array}$

               $\begin{array}{c}=98\mathrm{g}/\mathrm{m}\mathrm{o}\mathrm{l}\end{array}$

Basicity of ${\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_4$ =3

  $\begin{array}{c}\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{o}\mathrm{f}{\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_4=\frac{98}{3}\end{array}$

               $\begin{array}{c}=32.67\end{array}$

Thus,

  $\begin{array}{c}\mathrm{M}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{r}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{o}\mathrm{f}\mathrm{H}\mathrm{N}{\mathrm{O}}_3=\left(1+14+48\right)\text{ g/mol}\end{array}$

              $\begin{array}{c}=63\text{ g/mol}\end{array}$

Basicity of $\mathrm{H}\mathrm{N}{\mathrm{O}}_3$ =1

  $\begin{array}{c}\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{o}\mathrm{f}\mathrm{H}\mathrm{N}{\mathrm{O}}_3=\frac{63}{1}\end{array}$

               $\begin{array}{c}=63\end{array}$

Conclusion

The mathematical calculations shows option D is right and remaining options are wrong.