Q13.42 P - Chemistry: Molecular Nature Of Matter And Change

Question

Potassium permanganate (${\mathbf{KMnO}}_{\mathbf{4}}$ ) has a solubility of 6.4 g/100 g of  ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$  and a curve of solubility vs. temperature that slopes upward to the right. How would you prepare a supersaturated solution of  ${\mathbf{KMnO}}_{\mathbf{4}}$?

Step-by-Step Solution

Answer

The graph of the solubility vs temperature has an upward slope showing that increasing temperature will increase the solubility.

Therefore, the supersaturation will get started after the saturation level of potassium permanganate $KMn{O}_4$  is 0.065.

Step 1: Definition

Of the three types of solution, the supersaturated solution is formed when there is more solute settled down in the solution than the dissolved solute.

Step 2: Effect of Temperature

The solubility of the  $\mathbf{6}\mathbf{.}\mathbf{4}\mathbf{g}\mathbf{/}\mathbf{100}\mathbf{g}$ means 6.4 g of the potassium permanganate as solute dissolved in the 100g of the solvent.

The molar mass of the  ${\mathbf{KMnO}}_{\mathbf{4}}\mathbf{=}\mathbf{158}\mathbf{g}\mathbf{/}\mathbf{mole}$.

Therefore,

$$\begin{gathered} \mathrm{Saturation}=\frac{\mathrm{massofthesolute}}{\mathrm{massofthesolvent}} \\ \mathrm{Saturation}=\frac{6.5}{100} \\ \mathrm{Saturation}=0.065 \end{gathered}$$

The relation between solubility and temperature as per the graph is given below.

The solubility increases as the temperature increases forming an upward side graph shown in the graph for solid.

The supersaturated solution can be formed by adding more solute after the saturation level of the solution.