posted by Anonymous
How to find the volume of hot water required to dissolve the mass of acid, if we have 20g of benzoic acid contaminated with 0.4g of salicylic acid?
What is the mass of benzoic acid which participates when the solution is cooled to 20°C? Deduce.
What is the mass of salicylic acid which co-precipitated with the mass of benzoic acid?
What is the percentage of benzoic acid obtained after the recrystallisation?
Solubility (g/100ml) of BA at 20°C :0.29 and at 100°C:6.8
Solubility (g/100ml) of SA at 20°C:0.22 and at 100°C:6.67
When do these I ignore the water necessary to dissolve the impurity; often the minimum amount of H2O needed is just the amount to dissolve the major element and the impurity is dissolved in that same amount of water.
100 mL x (20g/6.67) = about 300 mL a 100 C.
How much will ppt at 20 C?
BA = 0.29 x (300/100) = about 0.9 lost.
SA = 0.22 x (300/100) = about 0.7 lost.
amount BA pptd 20-0.9 = ?
amount SA pptd 0.4-0.7 = 0