Q: A reaction has $$\Delta H = +5630 J/$$mol and $$\Delta S = +20.6 J/K$$·mol at $$T = 263 K. $$Calculate $$\Delta G$$ and determine if the process is energetically favorable.

$$\Delta G = +5630 - (263 \times 20.6) = -486 J/$$mol; favorable

Question 1

Which type of thermodynamic system can exchange both matter and energy with its surroundings?

Accepted Answer

Open system

Question 2

According to the first law of thermodynamics, what happens to the total energy in an isolated system?

Accepted Answer

It remains constant

Question 3

Which equation correctly represents the change in enthalpy ($$\Delta H) as a $$state function?

Accepted Answer

$$\Delta H = H_{final} - H_{initial}$$

Question 4

A process is at equilibrium when:

Accepted Answer

It is the lowest energy state and the forward and reverse rates are equal

Question 5

Which statement best describes entropy ($$S) in $$biological systems?

Accepted Answer

Entropy is a measure of disorder; systems tend to increase entropy

Question 6

For a favorable process in an open system, such as a living cell, which condition must be met?

Accepted Answer

$$\Delta S_{universe} \u003e 0$$

Question 7

Which equation represents the free energy change for a process at constant temperature and pressure?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 8

If $$\Delta G$$ for a reaction is positive, what does this indicate about the process?

Accepted Answer

The process is thermodynamically unfavorable

Question 9

Given the reaction: $$A + B \rightleftharpoons C + D$$, which equation represents the equilibrium constant ($$K$$)?

Accepted Answer

$$K = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 10

Which formula relates the free energy change ($$\Delta G) to $$the equilibrium constant ($$K$$)?

Accepted Answer

$$0 = \Delta G^\circ + RT \ln K$$

Question 11

Which of the following best explains why ATP hydrolysis is highly exergonic?

Accepted Answer

ATP hydrolysis relieves strain from closely spaced negative charges and forms stable products

Question 12

Which bond is cleaved during the hydrolysis of ATP to ADP?

Accepted Answer

Phosphoanhydride bond

Question 13

A reaction has $$\Delta H = +5630 J/$$mol and $$\Delta S = +20.6 J/K$$·mol at $$T = 263 K. $$Calculate $$\Delta G$$ and determine if the process is energetically favorable.

Accepted Answer

$$\Delta G = +5630 - (263 	imes 20.6) = -486 J/$$mol; favorable

Question 14

Which statement about coupling reactions in living systems is correct?

Accepted Answer

Coupling allows unfavorable reactions to proceed by pairing them with favorable reactions

Question 15

Which of the following is true about the sodium-potassium pump in cells?

Accepted Answer

It uses active transport, requiring energy to move ions against their concentration gradient

Question 16

Which equation describes the relationship between $$\Delta G$$, $$\Delta G^\circ$$, and the reaction quotient $$Q$$?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln Q$$

Question 17

Which process is thermodynamically favored at high temperature when $$\Delta H \u003e 0$$ and $$\Delta S \u003e 0$$?

Accepted Answer

$$\Delta G is $$negative; the process is favored

Question 18

Which of the following best describes the steady-state condition in living organisms?

Accepted Answer

The system is maintained in a constant state requiring continual energy input

Question 19

Why is ADP more stable than ATP?

Accepted Answer

ADP has fewer negative charges, reducing electrostatic repulsion

Energetics of Biological Systems: Thermodynamics and Bioenergetics

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