EX3

A solution contains 2.2x10-3M in CU2+ and 0.33M in LiCN. If the Kf for Cu(CN)42-- is 1.0x1025, how much copper ion remains at equilibrium?

Critique the accuracy of each of these statements.

A) Indicators such as methyl red provide accurate and precise measurements of pH.

B) According to the Arrhenius definition of acids and bases, ammonia qualifies as a base.

C) The strength of an acid or base changes as its concentration changes.

For the balanced equation shown below, if 98.0 grams of C2H3Br3 were reacted with 62.2 grams of O2, how many grams of Br2 would be produced? 4C2H3Br3+11O2=8CO2+6H2P+6Br2

87

What is the change in enthalpy (in kJ) under standard conditions when 246.4 g of sodium sulfate dissolves in water?

Answer:

A 1.250 g sample of barium chloride hydrate, BaCl2.xH2O, was heated until all the water had been driven off. The remaining anhydrous salt weighed 1.060g. Use this data to calculate the value of x, the number of moles of water of crystallization in the hydrated salt. You MUST Show ALL your work for full credit!












5. 0.0185 mol of hydrated magnesium sulfate MgSO4.xH2O has a mass of 4.56g. Calculate the value of x, the number of moles of water of crystallization in the hydrated salt. You MUST Show ALL your work for full credit!

Calculate the pH of a buffer that is 0.225 M HC₂H₃O₂ and 0.162 M KC₂H₃O₂. The K_a for HC₂H₃O₂ is 1.8

How do serine proteases hydrolyze dietary proteins? Describe the catalytic activity of chymotrypsin.

111 nmol of an antibody that binds strongly to the antigen protein G is covalently bound to the support of an affinity column with a void volume of 1.54 mL. The association equilibrium constant (K_A) for the binding of protein G to the antibody is 6.67 × 10⁸ M^–1 at pH 7.1. Calculate the retention factor for protein G on this column at pH 7.1.

k = ___

At pH 7.1 and a flow rate of 2.00 mL/min, how many minutes would it take protein G to elute from this column?

t_{r = ____} min

If a pH 3.2 elution buffer is applied to the column, protein G elutes at 3.48 min using a flow rate of 2.00 mL/min. Under these conditions, what is the association equilibrium constant between protein G and the antibody?

K_A = ____ M^-1

As we’ve seen before in this class, the roasting of limestone (calcium carbonate) to make quicklime (calcium oxide) and carbon dioxide is an important industrial process because the quicklime is used to make cement, among other things. How many kJ of heat are needed to produce 1.0 metric tons of quicklime?

Methanol, CH₃OH, is a nonelectrolyte; ammonia, NH₃, is a weak electrolyte; and calcium hydroxide, Ca(OH)₂, is a strong electrolyte. What are the solute particles present in aqueous solutions of each compound? (Select all that apply.)

If 0.1 mol of each compound is dissolved in solution, which one contains about 0.3 mol of solute particles, which contains 0.1 mol of solute particles, and which contains somewhere between 0.1 and 0.2 mol of solute particles?

. 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