General Chemistry Answers

Given the formula for change in internal energy, U = Q + W, calculate work for a

system that absorbs 350 kJ of heat and for which U = 150 kJ. Is the work done on

the system or by the system? Does the system expand or contract?

A sample biogas contains 10.75 mol ethane, 6.35 mol pentane and 2.89 mol propane. If the total pressure I 2. 46 atm, What are the partial pressures of the gases?

1. What is the boiling point and freezing point of a solution containing 6 g of

glycerol (C3H8O3) in 25 g of water?

2. What is the molecular mass of a solute in a solution containing 3.8 g of

nonelectrolyte in 420 g of water which freezes at -23 oC?

Identify what colligative property is applied or observed in the following. Explain

your answer.

1. Salt is mixed with ice in ice cream making.

2. Salt and sugar are used in food preservation.

3. Coolant is added to car radiators.

4. Pressure cooker.

5. Pruned or wrinkled fingers.

Solve for what is being asked.

What is the molar mass of the solute in a solution made by dissolving 34.41

g of an unknown nonelectrolyte compound in 280.0 g benzene. The boiling point of

the solution is 93.2 °C. Benzene has a boiling point of 80.1 °C and molal boiling-

point elevation constant of 2.53 °C/m.

What is the PH of a solution having the following H+ concentration?

a. 5*10^-3 M

b. 0.003M

c. 2.0*10^-6

Identify the Lewis acid in the following reaction.

a) ALCL₃ + CL^- ⤑ ALCL₄^-

b) BF₃ + NH₃ ⤑ BF₃ - NH₃

c) SiCL₄ + 2CL^- ⤑ SiCL₆^-2

d) PF₅ + F^- ⤑PF₆

In each of the reactions listed below, identify the Bronsted-lowery acids?

a. CH₃COOH (aq) + H₂O (l) CH₃COO^-(aq) + H₃0⁺ (aq)

b. HCN (aq) + SO4^-2 ↔ CN^-(aq) + HSO₄^-(aq)

c. HF (aq) + NH₃(g) ↔ F^-(aq) + NH₄⁺(aq)

d. HCIO₄(aq) + N₂H₄(aq) ↔ CIO₄^-(aq) + N₂H₅⁺(aq)

18. In a redox titration, potassium permanganate, KMnO4, was standardized using a 19.60 g/L

FeSO4(NH4)SO4.6H2O, (molar mass = 392.21 g/mol) standard solution. A 20.00 mL of the

standard solution, acidified with H2SO4 was put in a conical flask. A titre volume 15.50

mL of KMnO4 solution was required to reach the end-point. The titration reaction is:

Fe2+(aq) + MnO4

−(aq) → Fe3+(aq) + Mn2+(aq)

(i) Balance the above redox reaction in basic medium.

(ii) Calculate the molarity of the standard solution.

(iii) Determine molarity of MnO4-(aq) in the burette.

1.      Human colour vision is “produced” by the nervous system based on how three different cone receptors interact with photons of light in the eye. These three different types of cones interact with photons of different frequency light, as indicated in the following chart:

Cone Type   Range of Light Frequency Detected

S                          6.00-7.49 x 10¹⁴ s^-1

M                         4.76-6.62 x 10¹⁴ s^-1

L                          4.28-6.00 x 10¹⁴ s^-1

           What wavelength ranges (and corresponding colours) do the three types of cones

detect?