When Vo = 0.5× Vmax, [S] = 1× Km. Which of the following is true when [S] = 4× Km?

V0 = 40% of Vmax

none of these

V0 = 8% of Vmax

Vo = 80% of Vmax

Vo = 4% of Vmax

Question 1: Using Hard/Soft Acid/Base Concepts (HSAB) please decribe the following

a) Dimethylmercury, Hg(CH3)2, is one of the strongest known neurotoxins. Is it safe to mix mercuric fluoride, HgF2, with methyl lithium, LiCH3? Explain your decision.

b) Dimethylmagnesium, Mg(CH3)2, reacts violently with water, while Hg(CH3)2 is remarkably stable in aqueous environment. Explain this observation and provide a chemical equation for the reaction involving Mg(CH3)2.

Why is the “standard additions” a better method compared to the external calibration method?

Nitrous acid has a Ka of 4.0 * 10-4. in 1.00 L of solution, 0.670 moles of nitrous acid (HNO2) are added to 0.281 moles of NaOH. What is the final pH?

1. A 0.4243-g sample of CaCO 3 is dissolved in 12 M HCI and the resulting solution is diluted to 250.0 mL in a volumetric flask.
a) how many moles of the CaCO 3 are used (formula mass = 100.1)?
b) what is the molarity of the CA 2+ in the 250 mL of solution?
c) How many moles of Ca 2+ are in a 25.00 mL aliquot of solution in lb?

2. 25.00 mL aliquots of the solution from problem 1 are titrate with EDTA to the Eriochrome Black T end point. A blank containing a small measured amount of Mg 2+ requires 3.21 mL of the EDTA to reach the end point. An aliquot to which the same amount of the Mg 2+ is added requires 24.95 mL of the EDTA to reach the end point.
a) How many milliliters of EDTA are needed to titrate the CA 2+ ion in the aliquot?
b) How many moles of the EDTA are there in the volume obtained in part A?
c) What is the molarity of the EDTA solution?

3. A 100-mL sample of hard water is titrated with the EDTA solution in Problem 2. The same amount of Mg 2+ is added as previously, and the volume of EDTA required is 31.84 mL.
a) What volume of EDTA is used in titrating the Ca 2+ in the hard water?
b) How many moles of EDTA are there in that volume?
c) How many moles of Ca 2+ are there in the 100 mL of water?
d) If the Ca 2+ comes from CaCO 3+ How many moles of CaCO 3 are there in one liter of the water? How many grams of CaCO 3 are present per liter of the water?
e) If 1 ppm CaCO 3 = 1 mg per liter, what is the water hardness in ppm CaCO 3?

A 25.0 mL sample of 0.125 molL−1 pyridine (Kb=1.7×10−9) is titrated with 0.100 molL−1HCl.

Calculate the pH at one-half equivalence point.

Calculate the pH at 40 mL of added acid.

Calculate the pH at 50 mL of added acid.

A CHEM 2242 student dissolved 69.322 g of an unknown monoprotic acid in a 250 mL volumetric flask. The student then transferred 5.00 mL of this solution into a conical flask and diluted the 5.00 mL with another 85.00 mL of DI H₂O. Using the second derivative method the student estimated that equivalence occured when 36.86 mL of 0.1066 M NaOH titrant had been added. What is the molarity of the unknown acid solution?

A 80.0 mL sample of 0.0300 M HClO4 is titrated with 0.0600 M CsOH solution. Calculate the pH after the following volumes of base have been added.

(a) 17.2 mL pH = (b) 39.2 mL pH = (c) 40.0 mL pH =

(d) 40.8 mL pH = (e) 74.4 mL pH =

A sample of 7.60L of NH3 (ammonia) gas at 22 ?C and 735 torr is bubbled into a 0.300L solution of 0.400 M HCl (hydrochloric acid).

The Kb value for NH3 is 1.8

A 0.10 mol sample of AgNO3 is dissolved in a 1.00 L of 1.00 M NH3 (aq) solution. If 0.010 mol NaCl is added to this solution, will AgCl(s) precipitate? Show the procedure by which you arrive at your answer. Given that Kf of [Ag(NH3)2] + = 1.6 x 10^7 and Ksp of AgCl = 1.8 x 10^10 .

(a) If the molar solubility of Cd3(PO4)2 at 25 oC is 1.19e-07 mol/L, what is the Ksp at this temperature?

Ksp =

(b) It is found that 0.00178 g of Ag3PO4 dissolves per 100 mL of aqueous solution at 25 oC. Calculate the solubility-product constant for Ag3PO4.

Ksp =

(c) The Ksp of Sc(OH)3 at 25 oC is 2.22e-31. What is the molar solubility of Sc(OH)3?

solubility ________= mol/L

Hydrochloric acid (HCl) reacts with sodium carbonate (Na2CO3), forming sodium chloride (NaCl), water (H2O), and carbon dioxide (CO2). This equation is balanced as written: 2HCl(aq)+Na2CO3(aq)→2NaCl(aq)+H2O(l)+CO2(g)

Part A: What volume of 2.75 M HCl in liters is needed to react completely (with nothing left over) with 0.750 L of 0.400 M Na2CO3?

Part B: A 675-mL sample of unknown HCl solution reacts completely with Na2CO3 to form 18.1 g CO2. What was the concentration of the HCl solution?

4- Aspirin can be made in the laboratory by reacting acetic anhydride (C₄H₆O₃) with salicylic acid (C₇H₆O₃) to form aspirin (C₉H₈O₄) and acetic acid (HC₂H₃O₂). The balanced equation is:

            C₄H₆O₃   +   C₇H₆O₃     →     C₉H₈O₄   +   HC₂H₃O₂

            In a laboratory synthesis, a student begins with 3.00 mL of acetic anhydride (density = 1.08 g/mL) and 1.25 g salicylic acid. Once the reaction is complete, the student collects 1.22 grams of aspirin.Determine the limiting reactant, theoretical yield of aspirin, and percent yield for the reaction.

5.         Combustion analysis of a 13.42 g sample of equilin (which contains only carbon, hydrogen and oxygen) produces 39.61 g of CO₂ and 9.01 g of H₂O. The molar mass of equilin is 268.34 g/mol. Find the molecular formula of equilin.

Examine the effects of the detergent sodium dodecyl sulfate (SDS) on the binding activity of serium albumin (this detergent is a strong protein denaturant).

In a isolation of organic compounds phenanthrene, methyl 4-aminobenzoate and 1,4-dibromobenzene was dissolved in diethyl ether. HCl was used to separate the aqueous and organic layer. The aqueous layer contains methyl 4-aminobenzote +H⁺ +Cl^-. 6M NaOH was added to the aqueous layer, methyl 4-aminobenzote + water and NaCl was yield after the NaOH addition. This was followed by the addition of dichloromethane. After this addition you have two layers: one layer contains methyl 4-aminobenzoate + water +dichloromethane, the other layer contains water and NaCl.

(1)Can you explain and draw the reaction that takes place when HCl is added? Why was it necessary to add HCl?

(2)Can you explain and draw the reaction that happens when NaOH is added? why was it necessary to add NaOH?

(3) in a flask you had two layers one contained methyl 4-aminobenzoate, water and dichloromethane and the other layer contained water and NaCl. How can you identify the aqueous layer from the organic layer. Which layer is on top and which layer is on the bottom and why?

(4) when doing a crystallization a student is given a flask with phenanthrene, 1,4-dibromobenzene and diethyl ether. The solvent of choice for the crystallization is ethyal alcohol. Can you draw the reaction that takes place when ethyl alcohol is added to the flask containing: phenanthrene, 1,4-dibromobenzene and diethyl ether? Why was ethyl alcohol the solvent of choice? Do you think there is a better solvent of choice?