5. Explain the difference between a galvanic (voltaic) cell and an electrolytic cell. For a reaction in a galvanic cell, change in S is negative. Which of the following statements is true? Defend your answer.
a."E"willncrease with an increase in temperature.
b."E"will decrease with an increase in temperature.
c. "E" will not change when the temperature increases.
d.chG > 0 for all temperatures.
e. None of the above statements is true.
The main difference between a galvanic (voltaic) cell and an electrolytic cell lies in the nature of the chemical reactions that occur in each cell.
In a galvanic cell, the chemical reaction is spontaneous and releases energy, producing an electric current. It consists of two half-cells, each containing a metal electrode and a solution containing its corresponding ions. The reaction occurs spontaneously because there is a potential difference between the two half-cells.
On the other hand, an electrolytic cell is non-spontaneous and requires an external power source to drive the reaction. The chemical reaction in an electrolytic cell is non-spontaneous because the potential difference between the two half-cells is not sufficient to drive the reaction. The external power source provides the necessary energy to overcome this potential difference.
Now, let's consider the statement "For a reaction in a galvanic cell, change in S is negative." This statement is true because spontaneous reactions in a galvanic cell have a negative change in entropy (ΔS). This means that the reaction is occurring in a more ordered and less random state.
Now, let's analyze the given options:
a. "E" will increase with an increase in temperature.
This statement is not true. In a galvanic cell, increasing the temperature does not change the standard cell potential (E°). The change in temperature affects the rate of the reaction, not the cell potential. Therefore, this statement is false.
b. "E" will decrease with an increase in temperature.
This statement is also not true. As mentioned earlier, the standard cell potential (E°) does not change with temperature in a galvanic cell. Therefore, this statement is false.
c. "E" will not change when the temperature increases.
This statement is true. The standard cell potential (E°) does not change with temperature in a galvanic cell. Therefore, this statement is true.
d. ΔG > 0 for all temperatures.
This statement is not true. In a galvanic cell, the ΔG (change in Gibbs free energy) is negative, indicating a spontaneous reaction. Therefore, this statement is false.
e. None of the above statements is true.
This statement is not true. Statement c is true. Therefore, the correct answer is c. "E" will not change when the temperature increases.
To understand the difference between a galvanic (voltaic) cell and an electrolytic cell, let's first describe each type of cell.
A galvanic (voltaic) cell is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. In this type of cell, the reactants undergo spontaneous oxidation and reduction reactions, leading to the production of electrical energy. The chemical reactions in a galvanic cell are allowed to occur naturally, without the need for an external power source. An example of a galvanic cell is a standard battery.
On the other hand, an electrolytic cell is an electrochemical cell that uses an external electrical power source to drive a non-spontaneous redox reaction. Unlike a galvanic cell, an electrolytic cell enables chemical reactions that would not occur spontaneously by applying an external electric current to drive the desired reaction. Electrolytic cells are commonly used in various industrial processes, such as electroplating and electrolysis.
Now, let's examine the given statement and determine which option is true:
"For a reaction in a galvanic cell, change in S is negative."
The change in entropy (ΔS) refers to the difference in the entropy of the reactants and the entropy of the products. In a galvanic cell, spontaneous redox reactions occur, and such reactions often involve a decrease in entropy. This is because spontaneous reactions tend to proceed in a way that the reactants become more ordered or structured, resulting in a decrease in the randomness or disorder of the system. Thus, we can conclude that the given statement is correct.
Now, let's evaluate each option:
a. "E" will increase with an increase in temperature.
The potential difference (E) in a galvanic cell is determined by the difference in the reduction potentials of the electrodes and the concentrations of the species involved. Temperature does affect the value of the equilibrium constant for some reactions, which indirectly influences the cell potential. However, the direct effect of temperature on the cell potential is generally minimal. Therefore, this statement is not necessarily true.
b. "E" will decrease with an increase in temperature.
As explained above, the direct effect of temperature on the cell potential in a galvanic cell is generally minimal. Therefore, this statement is not necessarily true.
c. "E" will not change when the temperature increases.
This statement aligns with what we discussed earlier. The direct effect of temperature on the cell potential in a galvanic cell is typically negligible, so the statement is true.
d. ΔG > 0 for all temperatures.
The change in Gibbs free energy (ΔG) relates to the spontaneity of a reaction. In a galvanic cell, where the reactions are spontaneous, ΔG is negative. Therefore, this statement is false since ΔG is negative, not positive.
e. None of the above statements is true.
This statement is not correct because statement c, "E will not change when the temperature increases," is indeed true.
In conclusion, the correct answer is c. "E" will not change when the temperature increases, since the change in entropy (ΔS) is negative for a reaction in a galvanic cell, and the direct effect of temperature on the cell potential (E) is generally minimal.