18: Chemical Cells in Daily Life Flashcards
What is the definition of a chemical cell?
A chemical cell is a device that converts the chemical energy stored in it into electrical energy.
List the basic components of a chemical cell.
Negative electrode, positive electrode, electrolyte
What is the definition of the negative electrode?
It is the electrode from which electrons flow into the external circuit.
What is the definition of the positive electrode?
It is the electrode into which electrons flow into the external circuit.
What is the definition of electrolyte in a chemical cell?
It is a medium which allows ions to flow between the two electrodes.
What is the direction of flow of electrons when a light bulb is connected to a chemical cell?
The electrons flow from the negative electrode to the positive electrode in the external circuit.
In which situation is the voltage displayed in the digital multimeter positive?
A positive voltage is displayed when the positive electrode of the chemical cell is connected to its positive terminal and the negative electrode of the chemical cell is connected to its negative terminal.
In which situation is the voltage displayed in the digital multimeter negative?
A negative voltage is displayed when the negative electrode of the chemical cell is connected to its positive terminal and the positive electrode of the chemical cell is connected to its negative terminal.
What are the types of chemical cells?
Primary cells which cannot be recharged, and secondary cells which can be recharged.
List 3 types of common primary cells.
Zinc-carbon cell, alkaline manganese cell, silver oxide cell
List 3 types of common secondary cells.
Lead acid accumulator, nickel metal hydride (NiMH) cell, lithium ion cell
What is the definition of cell capacity?
Cell capacity is measured in ampere-hours, which is the number of hours a cell can supply a particular amount of electric current.
What is the definition of energy density?
Energy density is the amount of energy that can be derived per unit volume of the cell.
What is the definition of service life?
Service life is the length of time a cell can remain in use before its voltage drops to a certain value.
What is the definition of cycle life?
Cycle life is the number of charge-discharge cycles a secondary cell can undergo before its capacity falls to 80% of its original value.
What is the definition of shelf life?
Shelf life is the length of time a cell can be stored inactive before its capacity falls to 90% of its original value.
What is the material of the negative electrode of a zinc-carbon cell?
Zinc metal
What is the material of the positive electrode of a zinc-carbon cell?
Carbon
What is the material of the electrolyte of a zinc-carbon cell?
A moist paste of ammonium chloride
What is the material of the negative electrode of an alkaline manganese cell?
Zinc metal
What is the material of the positive electrode of an alkaline manganese cell?
Manganese(IV) oxide
What is the material of the electrolyte of an alkaline manganese cell?
Potassium hydroxide
What is the material of the negative electrode of a silver oxide cell?
Zinc metal
What is the material of the positive electrode of a silver oxide cell?
Silver oxide
What is the material of the electrolyte of a silver oxide cell?
Potassium hydroxide
What are the advantages of zinc-carbon cells?
Low cost
What are the advantages of alkaline manganese cells?
Good performance at all drain rates and steadier voltage over discharge
What are the advantages of silver oxide cells?
High energy density, constant voltage over discharge.
What are the applications of zinc-carbon cells?
For low drain devices like clocks and small radios.
What are the applications of alkaline manganese cells?
For moderate drain devices like motorised toys and smoke detectors.
What are the applications of silver oxide cells?
For watches, calculators, and hearing aids
What are the maximum voltages for zinc-carbon cells, alkaline manganese cells, and silver oxide cells respectively?
All 1.5 V.
What is the material of the negative electrode of a lead-acid accumulator?
Lead plates
What is the material of the positive electrode of a lead-acid accumulator?
Lead plates coated with lead(IV) oxide
What is the material of the electrolyte of a lead-acid accumulator?
Sulphuric acid
What is the material of the negative electrode of a NiMH cell?
Hydrogen-absorbing alloys
What is the material of the positive electrode of a NiMH cell?
Nickel oxyhydroxide
What is the material of the electrolyte of a NiMH cell?
Potassium hydroxide
What is the material of the negative electrode of a lithium ion cell?
Lithium atoms lying between graphite sheets
What is the material of the positive electrode of a lithium ion cell?
Lithium cobalt oxide
What is the material of the electrolyte of a lithium ion cell?
A lithium salt dissolved in an organic solvent.
What are the advantages of lead-acid accumulators?
Low cost
What are the advantages of NiMH cells?
High energy density, long cycle life, can withstand overcharge and discharge, environmentally friendly and safe.
What are the advantages of lithium ion cells?
High voltage, very high energy density, long cycle life, light
What are the applications of lead-acid accumulators?
For automotive SLI applications.
What are the applications of NiMH cells?
For hybrid electric vehicles like clocks and small radios.
What are the applications of lithium ion cells?
For portable electronic devices
What are the limitations of lead-acid accumulators?
High toxicity, low energy density, bulky, possibility of freezing and environmental and health concerns.
What are the limitations of lithium ion cells?
It is quickly damaged and may burst into flames if overcharged, it may be damaged if operated at a high pulse current for more than a few seconds.
What is the maximum voltage of one lead-acid accumulator?
2 V
What is the maximum voltage of one NiMH cell?
1.2 V
What is the maximum voltage of one lithium ion cell?
3.7 V
Why is the electrolyte of lithium ion cells not aqueous?
Lithium is highly reactive towards water and will react with aqueous electrolytes.
