Video Transcript
Which of the following statements
used generally to describe primary cells is incorrect? (A) Primary cells are impossible to
recharge. (B) Primary cells can be made in a
variety of different sizes, some of which are very small for mobile equipment. (C) Primary cells that contain
chemicals in their solid form are known as dry cells. (D) Primary cells stop working when
the anode material has been used up by the redox reaction. Or (E) primary cells transform
chemical energy to electrical energy through a spontaneous reversible redox
reaction.
Primary cells are a special kind of
galvanic cell. It is a galvanic cell that is not
reusable. Instead, it is used just once and
then discarded. Primary galvanic cells are
single-use electrochemical cells where electrons are generated spontaneously through
a redox reaction. These electrons pass through an
external circuit. Chemical energy is transformed into
electrical energy.
Another type of galvanic cell is
the secondary galvanic cell. In this cell, instead of only
transforming chemical energy to electrical energy, they can be recharged. In a secondary galvanic cell, an
external current is used to drive the redox reaction in the reverse direction,
therefore regenerating the reactants and allowing the cell to be used again.
Primary cells cannot do this. Their reactions are not
reversible. And as such, they are not
rechargeable. If we look at our answer choices,
we might initially feel that every statement correctly describes a primary cell. Primary cells are impossible to
recharge. Thus, option (A) is not incorrect
and is therefore not the answer to this question.
They come in a variety of sizes and
are known as dry cells when the chemicals used in the redox reaction are in solid
form. We know that primary cells stop
working when the reactants have been used up, so option (D) is not the answer
either.
They do also generate electricity
through a spontaneous redox reaction. But primary galvanic cells use a
redox reaction which is not reversible inside the cell. So the correct answer is (E). Primary cells transform chemical
energy to electrical energy through a spontaneous reversible redox reaction.
