Chemistry exam 25.05-2016

Question 1

General Chemistry – Short Questions

1. Write the Nernst for Cu2+/Cu electrode

Answer 1

The Nernst equation for an electrochemical half-cell is:

E = E⊖ − (RT/nF) lnQ 
E = E⊖ + (RT/nF) ln (aRed/aOx)

Question 2

2. Give 3 stabilizing factors for colloids

Answer 2

• Electrical charge
• Hydration (solvation)
• Protective colloids

Question 3

3. Give 4 examples of Chromatography that use the physical-chemical method of separation

Answer 3

• Adsorption chromatography
• Partition chromatography
• Ion exchange chromatography
• Gel chromatography

Question 4

4. Write the second law of Thermodynamics

Answer 4

Entropy is “nearly” conserved, which means any decrease of entropy in a given region of space is almost balanced by an increase in another region. In an isolated system, the entropy never decreases.

Question 5

5. Explain/write the equation for the relationship between Gibbs Free Energy and the Equilibrium Constant

Answer 5

∆G0 = -RTln(K)

Question 6

6. Write Avogadro’s Law

Answer 6

Equal volumes of any two gases at the same temperature and pressure contain the same number of molecules.

Question 7

7. Write the Ideal Gas Law

Answer 7

PV=nRT

Question 8

8. Give three postulates of the Kinetic Gas Theory

Answer 8

1) Gases are composed of molecules whose size is negligible compared to the average distance between them
2) Molecules move randomly in straight lines in all directions and at various speed. They collide each other and with the wall of the container
3) The average kinetic energy of the molecules of a gas depends upon the temperature

Question 9

9. Write Henry’s Law

Answer 9

The solubility of a gas I proportional to the partial pressure of the gas above the solution.

Question 10

10. Define/write the equation for Osmotic Pressure

Answer 10

Osmotic pressure π: Equal to the pressure that when applied to the solution
just stops osmosis
π = c. R. T
c = concentration (mol/dm3)
R = ideal gas constant
T = abs. temperature (Kelvin)

Question 11

11. Explain the Enthalpy change for KCl aqueous solution

Answer 11

…

Question 12

12. Name 2 surfactants

Answer 12

Soap and toothpaste

Question 13

3. Draw/name 3 alkaloids and 3 terpenes

Answer 13

Alkaloids: Nicotine, Coniine, Caffeine
Terpenes: Menthol, Phytol, Vitamin A (retinol)

Question 14

7. Write the reaction equation of the formation of a nucleotide

Answer 14

Nucleosides + Phosphoric acid →

nucleoside-5’-phosphate = nucleotide

Question 15

8. Name 3 examples aroma agents

Answer 15

Umami,
Miraculin,
Curculin,
L-glutamic acid

Question 16

9. Name 3 examples of mycotoxins

Answer 16

Ochratoxin A,
Trichothecenes,
Aflatoxin