Answer: The temperature of solution will decease along with the precipitation of solid lead nitrate in solution.
Step-by-step explanation:
Solubility of the substance is directly effect by the temperature of the solvent.
This is because the kinetic energy of the solvent increase as temperature increase due to which solvent easily breaks apart the solute particles easily and faster which will result in solubility of more solute in solvent and vice versa.
So, when prepared saturated solution of lead nitrate at 50°C was allowed to cool down to 30°C one will observe that the precipitation of solid lead nitrate in solution. And this means that solubility of lead nitrate with decrease in temperature decreases as well.