I need help with this packet. 20. A solution containing 4.0 g of n-butyric acid
ID: 552509 • Letter: I
Question
I need help with this packet.
20. A solution containing 4.0 g of n-butyric acid in a 100 mL of water was extracted twice with 50-mL portions of benzene Given the distribution coefficient, K (benzene/water), is 5.0 calculate the amount of n-butyric acid extracted from the water. Show all calculations 3 points) 21. Di scuss two reasons recrystallization typically gives crystals of high purity. (4 points) 22. Select the true statements about the melting of a solid. (2 points) (a) Melting is a phase change. (b) The enthalpy of fusion is typically larger than the enthalpy of vaporization. (c) Melting occurs with the vapor pressure of the solid equals that of the liquid. (d) The melting point is depressed by insoluble impurities, 23. The primary reason for the addition of anhydrous calcium chloride to an organic solvent is (2 points) (a) to remove traces of acid (c) to remove residual water (b) to remove color impurities (d) to remove dissolved salts. 24. Select the best approach to separate two immiscible liquid. (2 points) (a) separatory funnel (c) rotary evaporation (b) gravity filtration (d) simple distillation 25. Define azeotrope. (3 points)Explanation / Answer
20)Wn=[Vorg*Kd*W0/(VorgKd+Vaq)]
where W0=4 gm(for first extraction)=amount of acid dissolved in water
Kd=5=partition coefficient
Vaq=100ml=amount of water
Vorg=50ml=amount of liquid
wn=2.857142857g
after first extraction 2.857142857g extracted
W0=(4-2.857142857)g =1.142857143(for second extraction)
all other values are same
Wn=[1.142857143*5*50/(100+5*50)]
so Wn=.81632653(second extraction)
so total extracted=.81632653+2.857142857=3.673469387g
21)Dissolving both compound and impurities in appropriate solvent either the compound or impurities can removed from solution.Both compounds and impurity are dissolved in hot solution.Due to difference of solubity of compound and impurity in solvent either compound or impurity one remain in soution and another leave the solvent .so we get the pure solvent
22.True statements
a)Melting is a phase change
c)Melting occurs with the vapor pressure of the solid equals that of liquid(equilibrium)
23) c)The primary reason for the addition of anhydrous calcium chloride to an organic solvent is to remove residual water
24)a)Best approach to separate two immiscible liquid a)separatory funnel
25)Azeotrope:A mixture of liquids which has a constant boiling point and composition throughout distillation