5 2 chemical cells and fuel cells

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.

A voltage is produced in a chemical cell due to the difference in the ability of the electrodes to release electrons.

False. The more reactive metal in a chemical cell forms the negative electrode.

A greater difference in the reactivity of the metals causes a greater in the cell.

A battery is a combination of two or more chemical cells connected in series to give a larger overall voltage.

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.

False. The electrolyte used in a chemical cell does affect the voltage as different ions react with the electrodes in different ways.

Over time, the electrodes in a battery degrade as the reactions that occur there are irreversible.

An electrolyte is a substance that produces ions when dissolved in water or molten, allowing it to conduct electricity.

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. Alkaline batteries are non-rechargeable.

A fuel cell is an electrochemical cell in which a fuel donates electrons at one electrode and oxygen gains electrons at the other electrode.

A hydrogen-oxygen fuel cell produces water and energy.

The electrons flow from negative electrode to the positive electrode.

True. Hydrogen is pumped into the negative electrode compartment of the fuel cell.

The air containing oxygen is pumped into the positive electrode compartment.

The symbol equation for the reaction between hydrogen and oxygen to form water is: 2H2 + O2 → 2H2O

Three advantages of hydrogen fuel cells are:

Three disadvantages of hydrogen fuel cells are:

Fuel cells are less efficient at low temperatures.

The reaction that occurs at the positive electrode of a hydrogen fuel cell is: 4H+ + O2 + 4e- → 2H2O

The reaction that occurs at the negative electrode of a hydrogen fuel cell is: 2H2 → 4H+ + 4e-

False. In a hydrogen fuel cell, electrons flow from the negative electrode to the positive electrode through the external circuit.

The catalyst in a hydrogen fuel cell helps to speed up the reactions at the electrodes.

In hydrogen fuel cells, reduction is the process where oxygen gains electrons at the positive electrode.

The electrodes in a hydrogen fuel cell are typically made of porous carbon coated with a catalyst.

False. The movement of electrons through the external circuit creates the electric current in a fuel cell.