The solubility of at 40 C is around 64 g in 100 g water ot 0.64 g KNO3 in 100 g water.
Therefore 64 g KNO3 in 100 g water is required for satured solution.
According to the problem there are 35 grams of KNO3 dissolved in 100 grams water
So we need 64 g-35 g= 29 g more KNO3
Hence the correct answer is 1
Solubility:
When the maximum amount of solute is dissolve in the solvent is called solubility. On the basic of solubility the solution are following types:
Saturate solution:
A solution which contains the maximum amount of dissolved solute at the equilibrium is called saturated solution.
Un-saturate solution:
A solution which contains lesser amount of solute as compare to saturated solution. It will be able to dissolver more solute.
Super -Saturate solution:
A solution which contains the more dissolved amount of solute as compare to saturated solution.