Problem 31 - Chemistry The Central Science

Question

(a) What is the definition of the volt? (b) Do all voltaic cells produce a positive cell potential?

Step-by-Step Solution

Answer

(a) A volt (V) is the unit of electrical potential difference in the SI system, defined as the potential difference across which one joule of work must be done to move a positive charge of one coulomb from a lower to a higher potential point, represented mathematically as \( 1V = \frac{1J}{1C} \). (b) All voltaic cells produce a positive cell potential, as they rely on spontaneous redox reactions to generate electrical energy. If a cell produces a negative cell potential, it would be considered an electrolytic cell instead, requiring external energy to drive the non-spontaneous redox reaction.

Step 1: (a) Definition of a volt:

A volt (V) is the unit of electrical potential difference in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta. One volt is the electrical potential difference across which one joule of work must be done to move a positive charge of one coulomb from the lower potential point to the higher potential point. Mathematically, it can be expressed as: \( 1V = \frac{1J}{1C} \) where V represents the voltage in volts, J represents the work done in joules, and C represents the charge in coulombs.

Step 2: (b) Positive cell potential in voltaic cells:

A voltaic cell is an electrochemical cell in which a spontaneous redox (reduction-oxidation) reaction occurs, producing electrical energy. The cell potential, also known as the electromotive force (EMF), is the measure of the driving force that pushes the electrons through the external circuit. In general, a positive cell potential indicates that the redox reaction is spontaneous, and the cell can generate electrical energy. A positive cell potential would mean that the electrons would flow from the anode (the place of oxidation) to the cathode (the place of reduction) in the external circuit. So, do all voltaic cells produce a positive cell potential? In short, yes. To classify as a voltaic cell, the redox reaction must be spontaneous, which results in a positive cell potential. If it generated a negative cell potential, the cell would not be considered a voltaic cell, and the reaction would not be spontaneous. Instead, it would be an electrolytic cell, which requires an external energy source to drive the non-spontaneous redox reaction.