. What are the main characteristics of the mobile and stationary phases in gas

chromatography?

(10)

2. What are the main applications and advantages of temperature programming in GC? What

is the equivalent procedure in HPLC?

(20)

3. What is the purpose of derivatization in HPLC?

(10)

4. The following retention were measured in a column of 1.10 m:

air : 18.0 s.

methyl acetate: 1.98 min.

methyl propionate: 2.24 min

methyl n-butyrate: 7.93 min.

The base width of the three peaks were of 0.19, 0.23 and 0.79 min, respectively.

Calculate a) the number of theoretical plates in the column N

b) the equivalent height of a plate H

c) the length the column should have to obtain a resolution (Rs) of 1.5

for the acetate and the propionate

(20)

5.

Name two general methods for improving the resolution of two substances on a

chromatographic column.

(10)

6.

The distribution constant for compound X between n–hexane and water is 9.6. Calculate

the concentration of X remaining in the aqueous phase after an aliquot of 50.0 mL of

0.150 M of X has been treated by extraction with the following quantities of n-hexane:

(a)

One 40.0-mL portion;

(b)

Two 20.0-mL portions;

(c)

Four 10.0-mL portions;

(d)

Eight 5.0-mL portions.

What conclusion can you make from these calculations?

(20)

7.

Describe the principle of separation in a column used for size – exclusion

chromatography. What is the separation range in term of molecular weight? Give the

definition of “gel filtration: and “gel permeation

What is the solution to the problem of the abuse of pain medications? Use references to defend response.

(a) Potassium iodate solution was prepared by dissolving 1.022 g of KIO3 (FM 214.00) in a 500 mL volumetric flask. Then 50.00 mL of the solution was pipetted into a flask and treated with excess KI (2 g) and acid (10 mL of 0.5 M H2SO4). How many millimoles of I3− are created by the reaction

b) The triiodide from part (a) reacted with 37.57 mL of Na2S2O3 solution. What is the concentration of the Na2S2O3 solution?

(c) A 1.223 g sample of solid containing ascorbic acid and inert ingredients was dissolved in dilute H2SO4 and treated with 2 g of KI and 50.00 mL of KIO3 solution from part (a). Excess triiodide required 14.30 mL of Na2S2O3 solution from part (b). Find the weight percent of ascorbic acid (FM 176.13) in the unknown.
HINT: Think "back-titration

1. Draw a structural formula for a compound that is made of carbon and hydrogen.

2. What is the difference between:

     a. an ionic bond and a covalent bond

     b. a polar bond and a nonpolar bond

A solution is made by mixing 35.0 mL of ethanol, C2H6O, and 65.0 mL of water. Assuming ideal behavior, what is the vapor pressure of the solution at 20 ∘C? The relevant values at 20 ∘C are included in the table.

vapor pressure: Torr

Consider the following reaction: CO(g)+H2O(g)⇌CO2(g)+H2(g) Kp=0.0611 at 2000 K A reaction mixture initially contains a CO partial pressure of 1390 torr and a H2O partial pressure of 1770 torr at 2000 K.

A) Calculate the equilibrium partial pressure of CO2.

Write equations for the half-reactions that occur at the anode and cathode for the electrolysis of each of the following aqueous solutions.

Part A Ni(NO3)2(aq) Express your answers as chemical equations separated by a comma. Identify all of the phases in your answer.

Part B KCl(aq) Express your answers as chemical equations separated by a comma. Identify all of the phases in your answer.

Part C CuBr2(aq) Express your answers as chemical equations separated by a comma. Identify all of the phases in your answer.

Consider the equilibrium between COBr₂, CO and Br₂.

• COBr₂(g) <-->CO(g) + Br₂(g) K = 2.08 at 382 K

The reaction is allowed to reach equilibrium in a 14.6-L flask. At equilibrium, [COBr₂] = 4.50×10^-2 M, [CO] = 0.306 M and [Br₂] = 0.306 M.
(a) The equilibrium mixture is transferred to a 7.30-L flask. In which direction will the reaction proceed to reach equilibrium? right or left

(b) Calculate the new equilibrium concentrations that result when the equilibrium mixture is transferred to a 7.30-L flask.

1. if a buffer has a 4 charge and it is involved in removing two hydrogen ions from a solution, the buffers charge will become:

2. How many times more basic is a solution with a pH of 9 compared to a solution with a pH of 2?

3. What is the term used when describing an electrolyte becoming individual ions?

A weak base B (neutral charge) is dissolved in water at a concentration of 0.500 M. The concentration of the resulting ions is 0.170. What is the numerical value of Kb? The answer should be written to 4 decimal places and correct within +/-0.0020. Don't forget that [B] is going to be less than 0.500 M.

Sulfuric acid is the chemical produced in the United States with the highest volume of production. In one of the earliest processes used to make it, an ore containing iron pyrites (FeS2) is roasted (burned) with air. The following reactions take place in the roasting furnace: The gas leaving the reactor goes to a catalytic converter in which most of the SO2 produced is further oxidized to SO3: Finally, the gas leaving the converter passes through an absorption tower, in which the SO3 is absorbed in water to produce sulfuric acid (H2SO4). (a) An ore containing 82 wt% FeS2 and 18% inerts is fed to a roasting furnace. Dry air is fed to the furnace in 40% excess of the amount theoretically required to oxidize all of the sulfur in the ore to SO3, an FeS2 oxidation of 85% is obtained, with 40% of the FeS2 converted forming sulfur dioxide and the rest forming sulfur trioxide. Two streams leave the roaster: a gas stream containing SO2, SO3, 02, and N2, and a solid stream containing unconverted pyrites, ferric oxide, and inert material in the ore. Calculate the required feed rate of air in standard cubic meters per 100 kg of ore roasted and the molar composition and volume (SCMJ100 kg of ore) of the gas leaving the roasting oven.

Consider 100 g of 252Fm, which decays in a sequence of 5 α decays to eventually reach 232Th. The relevant half-lives follow:

252 Fm :25.39 hr

248 Cf :333.5 d

244 Cm : 18.10 yr

240Pu : 6564yr

236 U :2.34 × 10^7 yr

232 Th :1.41 × 10^10 yr

For the following questions, state clearly any approximations that you need to make. a) How much of the original sample is 252Fm and how much is 248Cf after one day? b) After one month? c) Explain why it is mostly curium after 5 years. d) What isotope is it mostly after 100 years? e) Approximately how long it will take the sample to be mostly thorium?

CH4(g) + Cl2(g)  CH2Cl2(g) + 2 HCl(g) Use the data in the table below to calculate the standard enthalpy, ∆H˚, for the reaction above. Substance CH4(g) CH2Cl2(g) HCl(g) ∆Hf˚, kJ•mol-1 –74.6 –95.4 –92.3

A 0.01 % solution of paracetamol API was analysed by HPLC giving a peak at 4.35 minutes from a c18 5 micron column. The peak area is 159785643. The peak area of a 0.05 % paracetamol standard is 80045687. Calculate the % assay for paracetamol API. Do you think this would comply with release specification of an active drug substance?

Ammonia rapidly reacts with hydrogen chloride, making ammonium chloride. Calculate the number of grams of excess reactant when 6.16 g of NH₃ reacts with 4.46 g of HCl