For calculations use C 12.011, H-1.007, O 15.999, 1, An unknown compound xis one

Question

For calculations use C 12.011, H-1.007, O 15.999, 1, An unknown compound xis one of four compounds listed in the table below. A mixture of x with mandelic acid melts at 118°C, a mixture of x with phenyl succinate melts at 1050C and a mixture of X with m-aminophenol melts at 1070C. Give the identity of X and explain your reasoning. (10 pts) mp, °C Compd. mandelic 119 acid Benzoic acid 121 121 Phenyl succinate 122 aminophenol 2, what effect does the presence of impurities in a compound have on the observed melting point? 3, What should you consider when choosing a solvent for recrystallization? (10pts) 4, In the extraction of caffeine, briefly explain the function of adding sodium carbonate (Na2CO3) (5pts)

Explanation / Answer

Question 1

The compound X is Mandelic acid. Because compound X melts with mandelic acid with its melting point. Compound X with other compounds shows reduced melting point. Hence the compound must be mandelic acid.

Question 2

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A substance (solid) containing soluble impurities usually melts at a lower temperature than the pure compound. It can also melt over a wide range of temperatures and is called the “melting point depression.” In general, the smaller the range of melting temperatures, the higher the purity of the sample

Question 6

MP = Melting point

BP = Boiling point

mL = Milli liter

g = gram

mol = Mole

mg = Milli gram

MeOH = Methanol

CH2Cl2 = Dichloro methane

RT = room temperature

D = Density

Question 7

Evaporation and filteration

Question 9

MgSO4 and Na2SO4 which are added in in organic solvent to remove water.

Question 11

Percentage recovery = 15 x 100 / 32 = 46.875 %

Question 12

Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase

Example : Camphor and Iodine,

Question 13

2.3 /122.123 = 0.0188 Moles (Molecular Weight: 122.123 g/mol)

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