Question

1. a. In an extraction experiment, in which three compounds are extracted from a solid mixture. Why would the percent recoveries be less that 100%? Please explain.

b. How do you know if the recystaillization was effective (did purification result)? Talk about melting points

Answer 1

1a. Always recovery cannot be 100% since the solubility curve is not 0 gm at 0°C temperature. Therefore some of the compound will remain in solution and the recovery always will be less than 100% . If u let me know what extraction exactly i can give still more points where we will lose yield. .

b. Recrystallization is a purification technique which is used to purify chemicals. if we dissolve both impurities and a compound in an appropriate solvent, there is a slow, selective formation of the crystal framework resulting either the desired compound or impurities can be coaxed out of solution, leaving the other behind. Then simple filtration will lead to the pure compound.

To check the purity range of the recrystallized compound we can check the melting point. If it is a pure compound the melting range will be with in 2-3⁰C . If any impurity is present then melting point range will increase . Hence from melting point range we can come to know that it is pure compound or presents with impurity