What is a chemical cell?
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What is a chemical cell?
A chemical cell is a source of electrical energy consisting of two electrodes made from metals of different reactivity immersed in an electrolyte and connected to an external circuit.
What causes a voltage to be produced in a chemical cell?
A voltage is produced in a chemical cell due to the difference in the ability of the electrodes to release electrons.
True or False?
The more reactive metal in a chemical cell forms the positive electrode.
False.
The more reactive metal in a chemical cell forms the negative electrode.
What is the relationship between the reactivity difference of metals and the voltage of a cell?
A greater difference in the reactivity of the metals causes a greater in the cell.
What is a battery?
A battery is a combination of two or more chemical cells connected in series to give a larger overall voltage.
In terms of chemistry, what is the main difference between rechargeable and non-rechargeable batteries?
The main difference is that in rechargeable batteries, the chemical reactions can be reversed by connecting to an external electrical supply, while in non-rechargeable batteries, the reactions are irreversible.
True or False?
The electrolyte used in a chemical cell has no effect on the voltage produced.
False.
The electrolyte used in a chemical cell does affect the voltage as different ions react with the electrodes in different ways.
What happens to the electrodes in a battery over time?
Over time, the electrodes in a battery degrade as the reactions that occur there are irreversible.
Define electrolyte.
An electrolyte is a substance that produces ions when dissolved in water or molten, allowing it to conduct electricity.
What causes a battery to "die" or go flat?
A battery "dies" or goes flat when one of the reactants is used up, and the products formed cannot be reverted back into reactants in non-rechargeable batteries.
True or False?
Alkaline batteries are non-rechargeable.
True.
Alkaline batteries are non-rechargeable.
What is a fuel cell?
A fuel cell is an electrochemical cell in which a fuel donates electrons at one electrode and oxygen gains electrons at the other electrode.
What are the products of a hydrogen-oxygen fuel cell?
A hydrogen-oxygen fuel cell produces water and energy.
Which direction do the electrons flow in a fuel cell?
The electrons flow from negative electrode to the positive electrode.
True or False?
Hydrogen is pumped into the negative electrode compartment.
True.
Hydrogen is pumped into the negative electrode compartment of the fuel cell.
Where is air containing oxygen pumped into a fuel cell?
The air containing oxygen is pumped into the positive electrode compartment.
What is the symbol equation for the reaction between hydrogen and oxygen to form water?
The symbol equation for the reaction between hydrogen and oxygen to form water is:
2H2 + O2 → 2H2O
State three advantages of hydrogen fuel cells.
Three advantages of hydrogen fuel cells are:
They produce no pollution,
They produce more energy per kilogram than petrol or diesel,
No power is lost in transmission as there are no moving parts.
State three disadvantages of hydrogen fuel cells.
Three disadvantages of hydrogen fuel cells are:
Materials used in producing fuel cells are expensive
High pressure tanks are needed to store oxygen and hydrogen, which are dangerous
Hydrogen is expensive to produce and store
How does temperature affect fuel cell efficiency?
Fuel cells are less efficient at low temperatures.
Write the half equation for the reaction that occurs at the positive electrode of a hydrogen fuel cell.(Higher tier only)
The reaction that occurs at the positive electrode of a hydrogen fuel cell is:
4H+ + O2 + 4e- → 2H2O
Write the half equation for the reaction that occurs at the negative electrode of a hydrogen fuel cell.
(Higher tier only)
The reaction that occurs at the negative electrode of a hydrogen fuel cell is:
2H2 → 4H+ + 4e-
True or False?
In a hydrogen fuel cell, electrons flow from the positive electrode to the negative electrode .
False.
In a hydrogen fuel cell, electrons flow from the negative electrode to the positive electrode through the external circuit.
What is the purpose of the catalyst in a hydrogen fuel cell?
The catalyst in a hydrogen fuel cell helps to speed up the reactions at the electrodes.
Define reduction in the context of hydrogen fuel cells.
In hydrogen fuel cells, reduction is the process where oxygen gains electrons at the positive electrode.
What material are the electrodes typically made of in a hydrogen fuel cell?
The electrodes in a hydrogen fuel cell are typically made of porous carbon coated with a catalyst.
True or False?
The movement of ions through the electrolyte creates the electric current in a fuel cell.
False.
The movement of electrons through the external circuit creates the electric current in a fuel cell.