An aqueous solution contains 0.480 M acetic acid. How many mL of 0.327 M potassium hydroxide would have to be added to 250 mL of this solution in order to prepare a buffer with a pH of 4.680?

(please explain. thank you!)

Balance each of the following half-reactions, assuming that they occur in basic solution. CH3OH(aq)?CH2O(aq)

A certain first-order reaction has a rate constant of 3.00×10⁻² s−1s−1 at 21 ∘C∘C. What is the value of kk at 51 ∘C∘C if EaEaE_1 = 76.0 kJ/molkJ/mol ?

Express your answer using two significant figures.

Another first-order reaction also has a rate constant of 3.00×10⁻² s−1s−1 at 21 ∘C∘C. What is the value of kk at 51 ∘C∘C if EaEaE_2 = 110 kJ/molkJ/mol ?

Express your answer using two significant figures.

Which of the following are generally required in a E2 reaction? Choose all that apply.

A. strong base

B. anti-coplanar orientation of eliminated groups

C. Primary or secondary substrate

D. Good leaving group

E. strong nucleophile

What is the molarity of a 7.48 m solution of ethanol (C2H5OH) if the density of this solution is 0.869 g/ml?

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