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Multiple Choice Questions on heat and energy

1) The standard free engery of a reaction is related to the equilibrium constant. How many KJ/mol change is required for the equilibrium constant to change by 10 at 25 degrees?
a.1.4 kj/mol
b. 5.6kj/mol
c.7.9kj/mol
d. 18.8kj/mol

2) Which thermodynamic function depends on the path taken from state 1 to state 2?
a. Internal energy
b. Enthalpy
c. Work
d. Free energy

3) What is Entropy change for a solution when a salt, such as MgCl2 is dissolved in water?
What is the change in entrophy upon solvation when a nonpolar molecule is mixed with water?
a. Increase
b. Decrease
c. No significant change
d. cannot predict

4) An important characteristic of living system is that they:
a. Always remain at equilibrium
b. Are perturbed from equilibrium only when experiencing stress
c. Are never at equilibrium
d. Are only at equilibrium when metabolic activity is low

5) Entropy is related to the number of states which are attained, all equivalent energy. What are the units of entropy?
a. Unitless
b. kj/mol
c. kj/mol-deg
d. kj

6) The hydrolysis of phosphate from which of the following molecules is least thermodynamically favorable?
a. ADP
b. Creatine phosphate
c. Gulcose phosphate
d. Phosphoenolpyruvate

7) ATP exhibits which of the following characteristic?
a. It is rapidly hydrolyzed in water
b. It is used for long-term engery storage in the cell
c. It is a kinetically stable molecule
d.It is a thermodynamically stable molecule

8) The standard transfere potential for the phophate group of phosphoenol-pyruvate(PEP) is -62kj/mol and that for ATP is -31kj/mpl. What is the standard free energy change for the transfere of a phosphate from PEP to ADP?
a. +31kj/mol
b. -31kj/mol
c.-93kj/mpl
d. +93kj/mol

9) The concentration of ATP in the muscle cells of some animals is found to remain relatively constant during periods when the muscles are contracting or at rest. This is because?
a. ATP is not the energy source utilized in muscle contraction
b. ATP is rapid depleted, but is also rapid synthesized to keep the concentration effectively constant
c. Glucose-6-phosphate is the main energy source in muscles
d. The amount of ATP consumed is insignificant

10) The high free energy change for the hydrolysis of a thiol ester, as found in acetyl-CoA, as compared to that for the hydrolysis of a simple ester, is partly due to:
a. The greater resonance stability in a simple ester due to a better p-electron overlap in a CO linkage than in a CS linkage
b. The gain in resonance energy in the product, acetate
c. The high value for the bond energy in the (S-C) bond
d. Reduction of the unfavorable electrostatic interactions in the acetyl-CoA

Solution Preview

The standard free energy of a reaction is related to the equilibrium constant. How many KJ/mol change is required for the equilibrium constant to change by 10 at 25 degreesC?

a.1.4 kj/mol
b. 5.6kj/mol
c.7.9kj/mol
d. 18.8kj/mol

Answer: b. 5.6kj/mol

A change of 1.4 kcal/mole (or 5.6 kJ/mol) in ΔGÂș changes K by approximately a factor of 10.

Which thermodynamic function depends on the path taken from state 1 to state 2?
a. Internal energy
b. Enthalpy
c. Work
d. Free energy

Answer: c. Work

State functions, like H and E, G , do not depend on the path taken during a reaction. These functions pertain only to the differences between the initial and final states of a reaction. However, heat (q) and work (w) are not state functions and their values are affected by the pathway taken.

What is Entropy change for a solution when a salt, such as MgCl2 is dissolved in water?

Entropy increases

From a highly ordered array of molecules in the solid state to a less ordered assemblage in the solution

Originally, the magnesium and chloride ions were arranged in a very tidy way in the crystal lattice - their entropy was low. (Remember that entropy is a ...

Solution Summary

Answers Multiple Choice Questions on heat and energy.

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