A reaction has a rate constant of 1.22*10^-4/s at 27 ⁰C and 0.230/s at 78 ⁰C. Determine the activation barrier for the reaction. What is the value of the rate constant at 18 ⁰C?

From the Fe2+ concentrations given determine the mg of Fe in the original vitamin tablet. You will need to convert ug/mL into mg of iron. You also have to consider that the original vitamin tablet sample was diluted to 250mL in a volumetric flask and then 5mL of that sample was diluted to 100mL in a volumetric flask. Please show all equations used and work done.

1. Concentration of 0.141738

2. Concentration of 0.1307058

3. Concentration of 0.1354047

Calculate the energy of the emitted photon as well as the wavelength and frequency of electromagnetic radiation emitted from the hydrogen atom when the electron undergoes the transition from n = 5 to n = 4.

A beaker with 195 mL of an acetic acid buffer with a pH of 5.000 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100 M. A student adds 6.20 mL of a 0.410 M HCl solution to the beaker. How much will the pH change? The pKa of acetic acid is 4.740.  

Refractive indices of aromatic molecules are higher than those of saturated hydrocarbons; for example, for benzene and cyclohexane, n=1.50112 and 1.4290 at 20C, respectivly. Can you suggest a reason for why n for C6H6 > n for C6H12?

2. You are given a pure protein sample to characterize and provided the following information:

Its molar extinction coefficient, ε280, is 0.30 liters micromole-1 cm-1

Its ΔGo for unfolding is 1.5 kcal/mol at 37o (where RT = 0.59 kcal/mole)

A) Using a 0.5 cm pathlength cell, you measure the absorbance at 280 nm of a 25- fold dilution of your pure protein in solution and find A280 = 0.45. What is the original concentration of the protein before dilution?

B) What is the concentration of the unfolded form of the protein in your sample?

It is relatively easy to study sodium vapor spectroscopically over boiling sodium at 1160 K. There is a question whether the molecule, N_a3 is linear or bent. Which would have the largest molecular partition function, q, at that temperature (N_a3 linear or N_a3 bent)? What molecular constants would need to be measured to determine this? (Assume that the bond strengths are teh same in each geometry and ignore electronic states.)

The solubility of O2 (g) in water at 0 oC = 14.74 mg/L. The solubility decreases to 7.03 mg/L at 35 oC.

Calculate kH (Henry’s Law Constant) for water at these temperatures.

partial pressure=0.21

Calculate the standard enthalpy change for the following reaction at 25 degrees C.

HCl(g) + NaOH(s) ---> NaCl(s) + H₂O(l)

Platinum has a specific heat of 0.133 J/gK. If 250.0 g of platinum at 1000.0°C is dropped into 115mL of water
at 20.0 °C, will the water boil?

Citric acid (192.13 g/mol) is a triprotic acid with the following chemical formula: H3C6O7H5.

The acid dissociation constants for citric acid are:

Ka1 = 7.1 x 10^-4 M; Ka2 = 1.7 x 10^-5 M; Ka3 = 6.4 x 10^-6 M

Describe how you would prepare at least 100.00 mL (you may make more) of a citrate buffer with a pH of about 4.40. You have available distilled water, volumetric flasks and any sodium salts you desire. You must indicate the amount in grams of material needed (except for water, you may use volume). Your designed buffer must have a reasonable buffer capacity and no solution you make can have a concentration greater than 0.500 M.

In the replacement reaction of magnesium nitrate with tin, how many grams of magnesium would be produced if 58.9 mg of magnesium nitrate? Report your answer with 3 significant figures.

2 Mg(NO3)2 + Sn → Sn(NO3)4 + 2 Mg

9.) As mentioned below, you are required to design your own procedure for determining the heat of dissolution of your chosen salt with a coffee cup calorimeter. Answer the following questions and consider them in designing this procedure:

a.) When you find your initial temperature Ti, should you take one measurement from the thermometer as soon as you place it in the water in the calorimeter? Why or why not? If not, what should you do instead?

b.) Do you expect the temperature of the water in the calorimeter to rise, fall, or stay the same after you add your salt? If the temperature will change, will it continue to change indefinitely or not?

c.) How will you know your dissolved salt solution has reached it's maximum or minimum temperature, i.e. what will you observe in your data to indicate this has happened?

d.) Should you repeat your experiment? Why or why not? If so, what could you change from trial to trial? (Think about what parameters you have control over and remember that you're trying to optimize your system!). Give two possible suggestions. Should you change both or just one? Which one would be easier to change from trial to trial?