Question:1

Calculate the density, in g/cm³, of a metal that has a volume of 41.3 L and a mass of 70.05 kg.

Question:2

You have 20.0 L of a 8.18% by volume (% v/v), water-based dye solution. Calculate the volume of pure dye and water that were used to prepare the solution. You may assume that volumes are additive.

Question:3

How many mL of pure (100.0%) food dye are needed to prepare 437.4 mL of 34.8% by volume (%v/v) food dye solution? You may assume that volumes are additive.

What is a cofactor? Give one example in the glycolysis pathway where a cofactor is involved.

A river is contaminated with 0.65 mg/L of dichloroethylene (C2H2Cl2). What is the concentration (in ng/L) of dichloroethylene at 21 C in the air breathed by a person swimming in the river (kH for C2H2Cl2 in water is 0.033 mol/L * atm)

What is the fraction of HA dissociated at a pH of 6.10 if Ka = 1.8 x 10-5? 0% 4% 100% 96%

Which of the following is true about the shape of the titration curve for a 0.1 M weak acid being titrated with a 0.2 M strong base as compared to a 0.1 M strong acid being titrated with a 0.2 M strong base?

The equivalence point volume will shift to the left.

It will start at a lower pH.

The equivalence point pH will be larger.

The equivalence point volume will shift to the right.

What is the volume at the equivalence point when 30.0 mL of 0.25 M HCl are titrated with 0.40 M NaOH at T = 298 K? K_w = 1.00 x 10^-14.

18.8 mL

30.0 mL

7.00 mL

37.6 mL

A 18.6 mL solution of 0.100 mol L-1 NaOH is titrated using 0.150 mol L-1 HCl. What is the pH of the solution after 15.3 mL of the HCl solution is added?

You are trying to find an appropriate solvent to use as a TLC mobile phase. Pure hexanes hardly move your sample from the baseline. Preferably, you would like to bring this sample spot to an Rf = 0.35, describe the steps you could take to accomplish this goal.

1. (3) Acetone is a more polar solvent than diethyl ether. With reference to the structures and specific functional group(s) of each molecule, why is cholesterol more soluble in acetone than lecithin is?

2. (2) In step 3 of the “Extraction and purification of Cholesterol,” the egg yolk is mashed with a spatula. What is the purpose of this step? ( consider how it helps with the following step(s) )

3. (2) In step 7 under “Extraction and purification of Lecithin,” acetone is added to the ether solution. Briefly describe the purpose of this step and how it helps isolate pure lecithin.

4. (3) At the end of the reaction, you may have excess materials. Where should you dispose of each substance below?

Acetone:

Cholesterol:

Diethyl ether:

Egg yolk:

Lecithin:

For each reaction write a balanced chemical equation and then below the chemical formula of each reactant and product write a brief description of the substance (color and physical state). Also, indicate whether the reaction is exothermic, endothermic, or cannot tell.

1. Combination Reaction

Equation:

Exothermic                  Endothermic                Cannot tell

Evidence of Chemical Change:

2. Reversible Decomposition--Combination Reactions

1. Dehydration of Blue Vitrol (Copper(II) Sulfate Pentahydrate)

Equation: CuSO₄·5H₂O ® CuSO₄ + 5H₂O

Exothermic                 Endothermic                Cannot tell

Evidence of Chemical Change:

2. Rehydration of Anhydrous Copper(II) Sulfate:

Equation: CuSO₄·5H₂O ® CuSO₄ + 5H₂O

Exothermic                 Endothermic                Cannot tell

Evidence of Chemical Change:

3. Single Replacement Reaction

Equation: Cu + 2AgNO₃ ® 2Ag + Cu(NO₃)₂

Exothermic                 Endothermic                Cannot tell

Evidence of Chemical Change:

4. Double Displacement Reaction--Milk from water:

Equation: CaCl₂ + Na₂CO₃ ® CaCO₃ + 2NaC1

Exothermic                 Endothermic                Cannot tell

Evidence of Chemical Change:

5. Mixed Type Reactions: The Alka-seltzer effect:

Equation: CaCO₃+ 2HCl ® CaCl₂ +H₂O + CO₂

Exothermic                 Endothermic                Cannot tell

Evidence of Chemical Change:

6. Three Penny Experiment

Please classify each of the following word equations as a chemical or physical change. Give evidence that supports your classification. (Hint, are all silver colored metals silver, or gold colored metals gold?)

red penny + zinc + zinc chloride solution ® silver penny + zinc + zinc chloride solution

Exothermic                 Endothermic                Cannot tell

Chemical or physical transformation?

Evidence of Chemical Change:

silver penny -®   gold penny

Exothermic                 Endothermic                Cannot tell

Chemical or physical transformation?

Evidence of Chemical Change:

The reaction of the persulfate ion with the iodine ion at room temperature is:

          S₂O₈^2-     +       2 I^-          ↔       2 SO₄^2-       +       I₂       ,     so   rate = k [S₂O₈^2-]^x [I^-]^y

The following data was collected at room temperature:

Determine the following:

(a) The rate law (including exponents for S₂O₈^2- and I^-)

(b) The rate constant, k          

2. A 155 g sample of iron metal at 120.0C is placed into 250.0 g of water at 20.0 °C in a calorimeter. When the system reaches thermal equilibrium, the temperature of the water in the calorimeter is 30.8C. Assume the calorimeter is perfectly insulated. What is the specific heat of iron? What is the amount of heat for 80.0 g piece of iron?

A protonated histidine residue in the active site of aspartate transcarbamoylase, ATCase, is thought to be important in stabilizing the transition state of the bound substrate.

A) Sketch a graph showing the pH dependence of the catalytic rate, assuming that this interaction is essential and dominates the pH-activity profile of the enzyme. Provide the biochemical basis for your graph.

B) The ATCase mechanism is known to proceed via an ordered mechanism. Draw a Cleland notation diagram showing how this reaction proceeds. Abbreviate the second substrate as CP. Two products are formed.  

Thank you!

7. Consider the titration of 100.0 mL of 0.120 M HNO2 titrated with 0.100 M NaOH. Determine the pH after each of the following situations. Show your calculations explicitly.

a.) No base has been added.

b.) 20.0 mL of NaOH has been added.

c.) 45.0 mL of NaOH has been added.

d.) 80.0 mL of NaOH has been added.

e.) 120.0 mL of NaOH has been added.

f.) 140.0 mL of NaOH has been added.

Suppose that you have to balance the following half-reaction in basic solution.

Cr₂O₇^2??(aq) ? Cr³⁺?(aq)

What is the coefficient on water of the final balanced half-cell reaction?

Consider the combustion of hydrochloric acid. 4 HCl (aq) + O2(g)  2H2O(l) + 2 Cl2(g) ΔHrxn = + 96.976 kJ/mol

B.If you place 750 mL of 0.500 M solution of HCl with 17.2 g of O2, will any oxygen remain? (Hint: limiting reagent problem)

C.What mass of chlorine gas (in grams) is produced?

D) How many molecules of Cl2 are produced based on part (B)

E) What mass of excess reagent remains after the limiting reagent is used up?

F) If the chemist collects 6.98 g of Cl2, what is the percent yield of the reaction? What is the percent error?

G) What is the enthalpy of the reaction for 24.5 g of HCl in presence of excess O2? Was energy absorbed or released into the surroundings?

In the pentose phosphate pathway draw out all the structures, with names, enzymes and cofactors, encountered in the conversation of glucose-6-phosphate to ribose-5-phosphate