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

Determination of a Molar Mass by Freezing Point Depression: This experiment used Stearic Acid

Experiments done in many first-year chemistry courses. They often use cyclohexane as the solvent and compounds such as p-dichlorobenzene, biphenyl, and naphthalene as the unknown solutes. Describe the advantages of this experiment over those.

Mass of antacid in sample: 1.5004 g

Antacid tablet: 1.6080 g

Composition of antacid:

Aluminum hydroxide: 160 mg

Magnesium carbonate: 105 mg

Molarity of EDTA: 0.01000 M

Pipet a 10.00 mL aliquot of the antacid sample solution to a 125 mL of Erlenmeyer flask followed by adding about 10 mL of the bicarbonate-carbonate buffer solution (pH 10.0 ± 0.1). Add about 3 mL of triethanolamine (TEA) and swirl the mixture for 2 min. to enhance the formation of Al-triethanolamine complex and to mask the Al-EDTA complexation. Set the solution aside until the turbid solution becomes mostly clear for easy observation of endpoint. Add 5 drops of Calmagite indicator and mix well. The solution should appear wine red color in this moment.Direct-titrate the solution with standard EDTA solution until the color changes to pure blue at the endpoint. The used volume of EDTA was 6.00ml. Hence, in this protocol quick titration will give an ideal result.

Compute the millimoles and weights of magnesium in the antacid sample solution and in the tablet.

1. How many grams O₂
   are needed to react completely with 2.60 mole FeS, in this reaction?      
   4 FeS + 7 O₂→2 FeO₃ + 4 SO₂

   		1.28 x 10 3 g
   		0.258 g
   		329 g
   		44.1 g
   		3.90 x 10 3 g
   		146 g
   		74.7 g
   		1.81 g

2. How many g of Aluminum are needed to react completely with 12.5 mole of Br₂, according to the chemical equation below?
   2Al + 3Br₂→Al₂Br₆
   

   		36.6 g
   		310 g
   		225 g
   		1.42 g
   		145 g

3. How many g of Aluminum are needed to react completely with 0.850 gram of Mn₃O₄, according to the chemical equation below?
   3 Mn₃O₄   + 8 Al --> 9 Mn    +    4 Al₂O₃

   		0.267 g
   		79.2 g
   		20.3 g
   		151 g
   		13.3 g
   		86.5 g
   		14.2 g
   		3.70 g

4. Refer to this equation:
   3SCl₂(l) + 4NaF(s) → SF₄(g) + S₂Cl₂(l) + 4NaCl(s)
   12.0 grams SCl₂ is reacted and 3.05 grams of SF₄ is formed. What is percent yield SF₄?
     
   Hint: find theoretical yield
   Hint: percent yield =(actual yield/ theoretical yield) x 100

   		19.3 %
   		64.4%
   		38.0%
   		27.2 %
   		82.1%
   		72.7%
   		90.1%
   		58.6%

5. Look at the following equation:   
      3H ₂ +   N ₂ ->   2 NH ₃
   
   If 85.0 gram of N ₂ gives 86.2 g of NH ₃, what is the percent yield of
   NH ₃?
   Hint: find theoretical yield
   Hint: percent yield =(actual yield/ theoretical yield) x 100

   		71.7 %
   		69.2 %
   		93.0%
   		45.1%
   		83.5 %
   		36.1%
   		79.2%
   		71.9%

A buffer is prepared by adding 2.78g of potassium acetate to 173mL of 1.25M acetic acid. What is the pH of the buffer? Write the net ionic equation for this buffered solution. (consider pH) How will the pH change if 0.100M HNO3 is added? (Assume volume change is negligible.) How will the pH change if 0.100M KOH is added? (Assume volume change is negligible.) Explain in words what would happen if .200M of HNO3 is added?

1. Explain if the concentration of the base increases, decreases, is not affected or cannot be calculated, for the following situations:

a) the concentration of the HCl solution was less than the actual value

b) when titrating the HCl sample, the tip of the burette contained air bubbles

c) an HCl sample greater than 10.0mL was measured by mistake

d) no indicator was added

e) the container where the HCl was poured was contaminated with acid