Question

How does Plaster of Paris help in repairing fractured bones?

Answer 1

Plaster of Paris:

• Plaster of Paris is obtained by heating Gypsum $({\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O})$ at $373\mathrm{K}$ .
• The formula of Plaster of Paris is ${\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$, which is also known as Calcium sulfate hemihydrate.

$\underset{\left(\mathrm{Gypsum}\right)}{{\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}\stackrel{373\mathrm{K}}{\to }\underset{(\mathrm{Plaster}\mathrm{of}\mathrm{Paris})}{{\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}$

• It is white in color and available in powder form.

Repairing of fractured bones:

• When Plaster of Paris is mixed with water, it absorbs water and changes back to gypsum, which is a hard mass in about half an hour with slight expansion in volume.
• This can be used as a plaster cast to fix fractured bones.
• $\underset{(\mathrm{Plaster}\mathrm{of}\mathrm{paris})}{{\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Water}\right)}{\frac{3}{2}{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\left(\mathrm{Gypsum}\right)}{{\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}$
• Doctors apply this plaster cast to keep the broken ends of the bones in proper position while they heal.