The half-life of cesium-137, released as a result of the Fukushima Daiichi nuclear disaster, is 30.2 years. Determine the number of years it would take for the amount of cesium-137 to decrease to 7 % of the original amount released in the disaster. Round your answer to the nearest number of years.

A 50.0 mL solution of 0.199 M KOH is titrated with 0.398 M HCl. Calculate the pH of the solution after the addition of the following amounts of HCl.

a) 0.00 mL HCl
b) 7.00 mL HCl
c) 12.5 mL HCl
d) 20.0 mL HCl

A. What is the ? (alpha)- helical dipole and what is the molecular origin of that dipole?

B. Identify two amino acids that are preferred in ? (beta)- sheets. Why might these amino acids be preferred?

C. Peptide bonds are believed to by hydrated by three water molecules, with one hydrogen bond donated from the N-H and two hydrogen bonds being accepted by the lone pairs of electrons in the carbonyl group. Would you expect a significant entropic component to be associated with the formation of secondary structures like alpha-helicies and beta-sheets. Explain.

How much of each of the solutions is needed to make the buffer? Final volume is 10 mL.

stock solutions

1 M HEPES (pH 7.9)

5 M NaCl

1 M BME

100 mM EDTA

750 mM MgCl2

50% glycerol

C) nuclear extraction buffer

20 mM HEPES

1 M NaCl

1 mM BME

0.5 mM EDTA

1.5 mM MgCl2

25% glycerol

Two moles of nitrogen gas at 25°C, confined within a cylinder by a piston maintaining a constant pressure of 1 atm, is heated with 5.30 kJ of energy. Assume all the energy is used to do work of expansion of the gas at 1 atm. What will be the final temperature of the gas? Recall ∆H = ∆E + P∆V and watch your units!

Consider the following reaction at 298 K: 4Al(s) + 3O2(g) ==> 2Al2O3(s)
Delta H= -3351.4 kJ/mol

Calculate:

a. Delta Ssystem = _______J/mol*K

b. Delta Ssurroundings = _______J/mol*K

c. Delta S universe = _________J/mol*K

Two amino acids are either not a standard alpha- amino acid or in the S configuration. Which
residues are they, and how are they different? Illustrate your reasoning with chemical
structures

Assuming that ?H

Why don't cationic and anionic polymerizations terminate by coupling?

. 25.5 g of NaCH3COO is added to a solution of 0.550M CH3COOH to a final volume of 500 mL4

. a. What is the pH? Ka = 1.8 x 10-5

b. What happens to the pH of the buffer above when 0.015 moles of OH- are added (no change in volume)?

c. What happens to the pH of the buffer above when 0.025 moles of HCl are added?

Data Table I: Freezing Point Depression

Calculations:

Show all work, including formulas used, units/substance labels, and evaluate significant figures when reporting your answer.

1.Calculate the freezing point depression (ΔT_f) for all four trials, assuming that the freezing point of pure water is 0^oC. Record these values in Data Table II.

2. Calculate the molality of each of the solutions (using the formula ΔT_f = K_f m, where K_f for water is -1.86^oC/m) using the values for freezing point depression you just determined in #1 above, and some algebra in the equation: ΔT_f = K_fm. Record these values in Data Table II.

3. Use these molalities to calculate the moles of solute (moles of ethanol and moles of isopropyl alcohol- remember that molality, m, is moles of solute/kg of solvent). Record these values in Data Table II.

4. The molecular formula for ethyl rubbing alcohol (ethanol) is C₂H₅OH (C₂H₆O) and for isopropyl alcohol is CH₃CHOHCH₃ (C₃H₈O). Calculate the mass of each alcohol in the solution (using the moles of each alcohol calculated in # 3, and the molar mass of each alcohol). Record these values in Data Table II.

5. Divide the mass of each alcohol calculated in # 4 by the density of that alcohol (the density of pure ethanol is 0.789 g/ml and that of pure isopropyl alcohol is 0.781 g/ml). The result will be the volume of the alcohol in mL that is present in the solution. Record this in Data Table II.

6. Divide this volume of alcohol by 2.0 mL and multiply by 100. The result is the % of alcohol in the solution. Record this value in Data Table II.

7. The alcohols you purchased are reported to be 70% pure. Compare the experimentally determined % of alcohol as calculated in # 6 to the accepted value of 70%, as a % error calculation (% error = │accepted value – experimental value│ / accepted value x 100 %). Record these values in Data Table II.

DATA TABLE II: FREEZING POINT DEPRESSION

A solution was prepared by dissolving 0.0170 mole of propionic acid and 0.0179 mole of sodium propionate in 1.00 L?

What would be the pH of the solution in beaker after 2.00 mL of 0.0154 M HCl were added to 10.0 mL of the prepared solution?

The transition of an electron from the principle quantum number n = 4 to n = 2 in atomic hydrogen causes emission of a photon of what wavelength?

Which of the following is the conjugate acid of H₂S?

Select one:

a. H3S+

b. H+

c. H2SO4

d. HS-

e. S

Which of the following is a weak acid?

Select one:

a. salicylic acid

b. hydrochloric acid

c. sulfuric acid

d. hydrobromic acid

e. nitric acid

Which of the following is the conjugate base of H₂S?

Select one:

a. SO2

b. S

c. OH-

d. SH-

e. H3S+

If the [H+] = 1.0 x 10^-9, what is the pH?

Select one:

a. 1.0 x 10-5

b. 1.0 x 10-9

c. 5

d. 1.0 x 10-14

e. 9

If the [H+] = 1.0 x 10^-9, what is the [OH-]?

Select one:

a. 1.0 x 10-14

b. 1.0 x 10-5

c. 5

d. 9

e. 1.0 x 10-9

Identify all allowable combinations of quantum numbers for an electron.

n=3,n=3, ?=2,?=2, m?=2,m?=2, ms=−12ms=−12

n=5,n=5, ?=4,?=4, m?=−1,m?=−1, ms=−12ms=−12

n=3,n=3, ?=−2,?=−2, m?=2,m?=2, ms=+12ms=+12

n=6,n=6, ?=6,?=6, m?=1,m?=1, ms=+12ms=+12

n=4,n=4, ?=3,?=3, m?=4,m?=4, ms=+12ms=+12

n=2,n=2, ?=0,?=0, m?=0,m?=0, ms=−1