91Ó°ÊÓ

According to the question, it is given that

The mass of propionic acid is 25.0 gand the molecular mass is 88 ml.\({\rm{Moles = }}\frac{{{\rm{Mass}}}}{{{\rm{Molar mass}}}}\)

\({\rm{Moles = }}\frac{{25}}{{88}}{\rm{ = 0}}{\rm{.284 moles}}\)

When calcium hydroxide reacts with propionic acid, the reaction is given by:

\({\rm{3Ca(OH}}{{\rm{)}}_2}{\rm{ + 2}}{{\rm{C}}_3}{{\rm{H}}_7}{\rm{COOH }} \to {\rm{ C}}{{\rm{a}}_3}{{\rm{(}}{{\rm{C}}_3}{{\rm{H}}_7}{\rm{COO)}}_2}{\rm{ + 6}}{{\rm{H}}_2}{\rm{O}}\)

As 3 mole of calcium hydroxide reacts with 2 moles of propionic acid then 0.284 moles of propionic acid will react with \(\frac{3}{2}{\rm{ }} \times {\rm{ 0}}{\rm{.284 = 0}}{\rm{.426 moles}}\)

According to the mole concept, the number of moles is the ratio of the mass of solute and the molecular mass of the solute. It is given that the number of moles of calcium hydroxide is 0.426 moles and molecular mass is 74 g/mol.

Thus, the mass of calcium hydroxide will be:

\(\begin{array}{l}{\rm{Mass}} = {\rm{Moles \times Molecular}}\,{\rm{Mass}}\\{\rm{Mass = 0}}{\rm{.426 }} \times {\rm{ 74 = 31}}{\rm{.524 g}}\end{array}\)