Question

1.The spontaneity of system or a biochemical reaction can be determined by:

A) Enthalpy alone

B) Entropy alone

C) Gibbs Free energy

D) Temperature and heat

2.A reaction in equilibrium where both forward and reverse reactions are proceeding equally, will have a DELTA G value of:

A) Positive

B) Zero

C) Negative

3.A reaction was originally endergonic, but became exergonic after reducing the temperature. Therefore, this reaction originally had __________ deltaH and a ______ delta S.

A) small positive, large positive

B) large positive, small negative

C) small positive, large negative

D) small negative, and equal small negative

E) Both B and C

4.As per the equilibrium constant relationship with the concentrations of the reactants and products, which of the following does NOT apply?

A) When reactant concentration is high, reaction proceeds in forward direction until excess reactant is used and equilibrium is restored.

B) When product concentration is high, the net reaction proceeds in the reverse direction.

C) Many biochemical processes in the cells are freely reversible

D) The direction of biochemical reactions in cells, the direction of reaction can shift as the reactants or products are removed from the cell

E) All metabolic reactions in our cells are reversible; none can be irreversible.

5.Any deviation of a reversible reaction from equilibrium will stimulate a process that tends to shift the reaction such that the equilibrium is restored again. This principle is known as:

A) LeChatelier Principle

B) Equilibrium Principle

C) Reversible reaction Principle

D) Restoration Principle

5.Keq although is a constant, it remains constant at specific temperature. When the temperature, varies, Keq can vary.

A) True

B) False

6.A graph (plot) of ln Keq vs. 1/T helps us determine delta H° and delta S°. Such a plot is known as:

A) Equilibrium plot

B) van’t Hoff plot

C) Thermodynamic plot

D) Temperature dependence plot

7. “Standard States” in thermodynamics refers to:

A) 1M concentration (or activity 1) for solutes when dissolved

B) Undissolved solutes in their free state is just 1 or unit, no concentrations

C) Pure solvents have unit value (1)

D) Pressure is 1 atmosphere for gases

E) All of the above

8.For biochemicals in living organisms, for concentrations and standard states, which of the following does NOT apply?

A) Biochemicals in living organisms are also at concentrations of 1M

B) The biochemical standard state for hydrogen ion concentration is 1 x 10-7 because of almost neutral pH; not 1Molar

C) The standard free energy change is given the symbol GO ’ instead of GO

D) Standard free energy changes and other thermodynamic parameters according to biochemical convention are valid only at pH 7.0

9. An “open system” refers to:

a) A system that freely exchanges energy with the surroundings

b) A system that freely exchanges matter with the surroundings

c) A system that freely exchanges both energy and matter with the surroundings

d) A system that neither exchanges energy nor matter with the surroundings

Answer 1

ANS.1

Here the answer is C. So we can say the spontaneity of a system or a biochemical reaction can be determined by Gibbs free energy given by the equation where. is the change in Gibbs free energy. is the change in enthalpy. is the temperature and is the change in entropy. When < 0 the reaction is favourable or spontaneous. When > 0 the reaction is unfavourable or non-spontaneous.

ANS.2

Here the answer is B. A reaction in equilibrium where both forward and reverse reactions are proceeding equally will have a Delta G value zero.

ANS.3

Here the answer is B. A reaction was originally endergonic but became exergonic after reducing the temperature. Therefore this reaction originally had large positive delta H and a small negative delta S.

ANS.4

Here the answer is E.

ANS.5

Here the answer is A. Any deviation of a reversible reaction from equilibrium will stimulate a process that tends to shift the reaction such that equilibrium is restored again. This principle is known as LeChatelier principle.

ANS.5

Here the answer is A or True. Keq although a constant remains constant at a specific temperature. When the temperature varies Keq can vary.

ANS.6

Here the answer is B. A graph plot of ln Keq vs. 1/T helps us determine delta H⁰ and delta S⁰ . such a plot is known as Van't Hoff plot.

ANS 7.

Here the answer is E. Standard states in thermodynamics refers to all the given conditions or all of the above.

ANS.8

Here the answer is A. For biochemicals in living organisms for concentrations and standard states,the next statement does not apply. Biochemicals in living organisms are also at concentrations 1M.

ANS.9

Here the answer is C. An open system refers to a system that freely exchanges both energy and matter with the surroundings. Examples are an ocean, human being, an open beaker etc.