The rate determining step in a reaction mechanism:

A. is the fast step

B. is the slow step

C. is always the first step

D. is the transition state

In the laboratory, a quantity of I2 was reacted with excess H2 to give 0.650 moles of HI. It is also known that the percent yield of this reaction was 46.0%. How many moles of I2 reacted? (Hint: Write a balanced equation.)

Hydrogen azide (HN3) is a shock-sensitive liquid, which means it explodes when subjected to a physical shock. The HN3 molecule contains two N-N bonds with bond lengths 113 pm and 124 pm. The H-N-N bond angle is 112°. Draw two Lewis structures of HN3 that obey the octet rule. What is the formal charge of each atom in your structures? Which structure is most consistent with the experimental data?

a)Assume the reaction 2Fe3+ + Sn2+ -> 2Fe2+ + Sn4+ has a rate law v = k[Fe3+][Sn2+]. If Fe2+ is produced at a rate of 0.12 mol L-1 s-1 when the reactant concentrations are 0.30 mol L-1 for Fe3+, and 0.40 mol L-1 for Sn2+, then what is the value of the rate constant, k ? Quote your answer to 2 decimal places.

Answer L.mol-1.s-1

b)

The half-life for the decomposition of a gaseous sample of thioketene, H₂C=C=S at 500 Pa is 42 s. When the thioketene pressure is 250 Pa the half-life is 21 s. Determine the order of the reaction, entering your answer as a number.

c)

At 1100 K, acetic acid decomposes via 2 competing, first order reactions:

CH₃COOH -> CH₄ + CO₂,   k₁ = 3.4 s^-1

CH₃COOH -> CH₂=C=O + H₂O,    k₂ = ? s^-1

The half life of acetic acid at this temperature is 0.10 s. What is the value of the rate constant, k₂?

d)

At 1100 K, acetic acid decomposes via 2 competing, first order reactions:

CH₃COOH -> CH₄ + CO₂,   k₁ = 4.1 s^-1

CH₃COOH -> CH₂=C=O + H₂O,    k₂ = ? s^-1

At 1100K, the yield of ketene (CH₂=C=O) is 71.5%. Estimate the rate constant, k₂, for the second reaction

e)

The following mechanism has been proposed for recombination of iodine atoms:

I + I -> I₂*, k₁ = [k1].0

I₂* -> I + I, k_-1 = [k-1].0

I₂* + M -> I₂, k₂ = [k2]

What is overall rate constant if k₁ = 4, k_-1 = 4 and k₂ = 0.04?

f)

The following mechanism has been proposed for recombination of iodine atoms:

I + I -> I₂*, k₁ = 9.0

I₂* -> I + I, k_-1 = 5.0

I₂* + M -> I₂, k₂ = 0.04

What is overall rate constant?

.

1. Describe how you would prepare 1.50 L of a 0.500 M phosphate buffer with a pH of 7.5. (show work)

2. If 5.00 mL of 0.150 M HCl is added to 0.750 L of your buffer from (1), what will the new ph be? (show work)

3. If 10.00 mL of 1.50 M NaOH is added to 0.750 L of your buffer from (1), what will the new ph be? (show work)

One facet of the central field approximation for many-electron atoms is that inner-shell electrons screen the nuclear charge. To understand how this works quantitatively, first note that the probability distributions for electrons in different shells generally do not overlap much. For instance, the electrons in the M shell (n=3) are almost always farther from the nucleus than the electrons of the K (n=1) and L (n=2) shells. Thus, it is a good approximation to assume that the inner shells completely screen the nucleus from the outer shells. For example, if there are ten electrons altogether in the K and L shells of an atom, then the electrons in the M shell experience force from a charge of roughly Z−10, where Z is the charge on the nucleus as an integer multiple of e, the magnitude of the charge on an electron. This is called the effective nuclear charge Zeff. Part A In a beryllium atom (Z=4), how many electrons are in the K shell? Part B In xenon (Z=54), what is the effective charge Zeff experienced by an electron in the M (n=3) shell? Part C How many electrons are there altogether in the K, L, and M shells of xenon? Recall that for n=3, the orbital quantum number l must be zero, one, or two and that ml can take any value between postive and negative l. Part D The energy for the 5p valence electron in indium (Z=49) is −5.79 electron volts. What is the effective nuclear charge Zeff experienced by this electron?

1)Use the balanced chemical equation below to calculate the mass of KCl that is formed for every 164 L of O2(g) produced. You may assume the reaction takes place at STP.

2 KClO3(s) → 2 KCl(s) + 3 O2(g)

2)Identify the limiting reactant and calculate the theoretical yield of CO2(g), in grams, if 21.5 L of C3H8(g) reacts with 96.1 L of O2(g) according the the balanced chemical equation below.

C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)

2,3 BPG is quite abundant in red blood cells (~4.5 mM) and it modulates the affinity of hemoglobin for oxgen. Briefly explain what BPG is doing to the affinity of hemoglobin for oxygen.

1. Glucagon inhibits glycolysis in the liver because:
a.) it increases the activity of Fructose-bisphosphatase 2
b.) it causes a decrease in Fructose-2,6-bisphosphate concentration 
c.) it decreases the activity of Phosphofructokinase-2
d.) it causes a decrease in Fructose-2,6-bisphosphate concentration 
e.) all of the above

2. Glucagon:
a.) is a hormone that is structurally similar to tyrosine
b.) is produced by the pituitary gland
c.) works with epinephrine to increase the supply of glucose to muscle cells
d.) is detected by a signal transduction pathway that utilizes IP3
e.) both b and c

1) What is the pressure in a 18.2-L cylinder filled with 27.0g of oxygen gas at a temperature of 329K ?

2) A gas mixture with a total pressure of 765mmHg contains each of the following gases at the indicated partial pressures: CO2, 129mmHg ; Ar, 208mmHg ; and O2, 191mmHg . The mixture also contains helium gas.

What mass of helium gas is present in a 12.4-L sample of this mixture at 276K ?

Calculate the pH values of the following solutions (you must show the procedure of calculations:

a-mole of formic acid and 0.02 mole of NaOH diluted to 1L. (formic acid pK=3.75).

b-An aspartic acid solution if the alpha carboxyl is 1/2 dissociated. (aspartic acid pK1= 2.0, pK2=9.9, pKside=3.9)

Give me two reasons for deviations from Beers’ law that would cause a nonlinear relationship

between absorbance and concentration. Explain why the deviations from linearity occur.?

15.7 g of H₂ gas is mixed with 294 g of I₂ gas in a 5.00 L tank at 25 ºC. The two gasses react to form hydrogen iodide gas by the reaction H₂(g)+I₂<->2HI(g). Given K=710 at ºC, what are the equilibrium concentrations of each gas? (Answers are listed in order of [H₂], [I₂] and [HI].)

a.1.560, 0.230, 0.000 b.0.000, 1.560, 3.120 c.1.330, 0.000, 0.460 d.1.328, 0.000230, 0.464

a start up company is trying to produce its own brand of antibacterial ointment. it decides to analyze a generic brand already on the market so that it can make suitable modification to the chemical composition. its known that the generic ointment contain benzoic acid( active ingredient), benzhydrol (the fixative) and anise, which add fragrance. you are a part of development team that wishes to separate these three substances in order to determine their relative proportions in the ointment, as well as to discover any inactive or unlisted constituents. some member of your team were able to isolate the inactive ingredient; However, NMR reveals that you still have a mixture of benzoic acid, benzhydrol, anisole left unseparated. as a member of team, you have been asked to do the following: 1. design an experiment to separate the following compounds from a mixture using any combination of purification techniques (TLC, column chromatography, Extraction and recrystallization) 2. carry out characterization studies such as melting point, IR, NMR to confirm that your purification was successful. 3. determine the percent recovery of the individual components of the mixture. mixture originally contained; 0.5g benzoic acid, 0.25g benzhydrol, 0.25ml anisole and 10ml diethyl ether.