Question

Question 17 1 pts What solubility properties are important in the selection of a solvent for recrystallisation? sparingly soluble in hot solvent and readily soluble in cold solvent readily soluble in both hot and cold solvent sparingly soluble in both hot and cold solvent readily soluble in hot solvent and sparingly soluble in cold solvent Question 18 1 pts How would you modify the procedure given in the Laboratory Manual if you did not know which solvent to use? if the sample is not soluble in water it can not be recrystallised test different solvents to see if the sample is more soluble in the hot solvent than the cold test different solvents to see if the sample is more soluble in the cold solvent than the hot test solvents to find one the sample is not soluble in

Answer 1

Answers:

16 - d

13 - c

14 - b

17 - d

18 - b

15 - b

14 The most importan in the selection solvent a of it is soluble in cold solvent. sparingly for recrystallization recrystallization is lintarle readily soluble in hot solvent and this is the erucial solubility property for recrystalization. Always remember that Recrystallization is based on the principle of estubility: Compounds tend to be (Solulis) liquids (solvente) Than liquids. you to weht • test different solvents to see if the sample more soluble They are in cold in hot They do not know which the procedure if you (18) How do solvent the sample is more soluble in the hot solvent than the cold. the exp has been stated in the above answer. explanation iple be 156 tube ? it into the more More why should the M.P. Sample finely powdered before capillary Note that if the cample is finely powdered, it makes the melting point reading surface exposed evenly Therefore, heating. accurate because and heat is distributed even area correct answer is: even area • increases surface

(16) why Sila hupung tightly packed etig transfer into the should the M.P. be sample into The tube? in tubes because it makes Thé heat fanuple more and It also enhanced the the overall easier automated detection of the melt. Sample for isi : The Correct on the above explanation is Samples efficient and packed in capillary taber because it makes reproducible. It also of anewee based uneven remove air pockets which would (and an source in a common 13) the most ple is : neey tallized The o another presence of an residue been added to the product during Thé of impurity sample compound. The other compound could be a of the reactant used in the experiment or any other contaminants that expertinentál poeta (W) To determine if the unknown.com compound it pare? degrece. Pure substances generally metting range two degrees. Impuritate depress might have 1-2 one or have a broaden the me lend to metting range