Electrochemistry Key Concepts

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Questions and Answers

Which factor does not directly influence the cell potential of an electrochemical cell, as described by the Nernst equation?

Number of electrons transferred in the cell reaction
Concentration of reactants and products
Volume of the electrolyte solution (correct)
Temperature

During the discharge of a lead-acid battery, what happens to the specific gravity of the electrolyte and why?

Decreases due to the consumption of sulfuric acid. (correct)
Fluctuates unpredictably with temperature.
Increases due to the production of water.
Remains constant as the sulfuric acid concentration is maintained.

Which of the following best describes the function of a salt bridge (or porous membrane) in an electrochemical cell?

To facilitate direct electron transfer between the two half-cells.
To provide a physical barrier against gas evolution.
To measure the potential difference between the two electrodes.
To prevent the mixing of electrolyte solutions while allowing ion flow to maintain charge neutrality. (correct)

What distinguishes a primary battery from a secondary battery?

Secondary batteries are rechargeable, while primary batteries are not. (D) Signup and view all the answers

According to the Tafel equation, how does an increase in overpotential affect the rate of an electrochemical reaction?

It increases the reaction rate exponentially. (B) Signup and view all the answers

What is the primary advantage of using a lithium-ion battery over a nickel-cadmium (Ni-Cd) battery?

Higher energy density and no memory effect (C) Signup and view all the answers

In a Proton Exchange Membrane Fuel Cell (PEMFC), what is the role of the proton exchange membrane?

To conduct protons from the anode to the cathode while preventing electron flow. (B) Signup and view all the answers

Which of the following is the correct half-cell reaction occurring at the cathode of a Leclanche cell (dry cell)?

$MnO_2(s) + H_2O(l) + e^- \rightarrow MnO(OH)(s) + OH^-(aq)$ (C) Signup and view all the answers

What is the primary function of a reference electrode in electrochemical measurements?

To provide a stable and known potential against which other electrode potentials can be measured. (D) Signup and view all the answers

How does increasing the temperature typically affect the performance of a battery?

It can increase the initial capacity and performance, but prolonged exposure to high temperatures can decrease lifespan. (A) Signup and view all the answers

What is the major advantage of using biofuel cells compared to traditional fuel cells?

Lower operating temperatures and use of renewable fuels (C) Signup and view all the answers

What is the 'storage density' of a battery primarily a measure of?

The amount of energy stored per unit volume or mass. (B) Signup and view all the answers

Which of the following factors primarily determines the capacity of a battery?

The amount of active material in the electrodes. (C) Signup and view all the answers

In the context of electrochemical reactions, what does the term 'overpotential' refer to?

The difference between the actual electrode potential and the equilibrium potential required to drive a reaction at a certain rate. (D) Signup and view all the answers

What is a key disadvantage of lead-acid batteries compared to lithium-ion batteries?

Lower energy density and use of toxic materials (D) Signup and view all the answers

What is the main purpose of using a Duracell battery (alkaline battery) over a standard Leclanche cell?

To provide a longer shelf life and more consistent voltage during discharge. (B) Signup and view all the answers

Which of the following best describes the function of the electrochemical series?

It ranks elements according to their standard electrode potentials, indicating their relative reactivity. (D) Signup and view all the answers

In a thermal battery (reserve battery), how is the battery activated?

By melting a solid electrolyte using a built-in pyrotechnic heat source. (A) Signup and view all the answers

How is the 'energy efficiency' of an electrochemical cell or battery calculated?

Ratio of electrical energy output to the chemical energy input. (D) Signup and view all the answers

What primarily affects the rate of ion transport within the electrolyte of a battery?

The viscosity and ionic conductivity of the electrolyte. (B) Signup and view all the answers

Flashcards

Faraday's Laws

Relates the amount of substance produced or consumed at an electrode to the electric charge passed through the cell.

Origin of Potential

The potential difference between an electrode and its electrolyte, arising from charge separation at the interface.

Electrochemical Series

A list of elements organized by their standard electrode potentials, predicting the spontaneity of redox reactions.

Nernst Equation

Relates the electrode potential to the concentrations of the reactants and products in a redox reaction.