Chemical Cells & Fuel Cells Flashcards
All 10 cards in this deck
What three things are needed to make a simple chemical cell?
Two different metals as electrodes, dipped in an electrolyte, connected in a circuit.
Why does a simple chemical cell produce a voltage?
e.g. zinc and copper in sodium chloride solution
Because the two metals have different reactivities, so electrons flow through the wire from the more reactive metal to the less reactive one.
Here, electrons flow from the zinc to the copper.
Why does the voltage of a chemical cell fall to zero over time?
Because one of the reactants is used up, so the reaction stops.
What happens to the reading on the voltmeter over a long period of time in a cell made from copper and iron in sodium chloride solution?
It shows a constant voltage, then decreases, and finally falls to V.
How does the size of the voltage produced by a chemical cell depend on the two metals used?
e.g. magnesium/copper compared with zinc/copper
The greater the difference in reactivity between the two metals, the greater the voltage.
Magnesium/copper gives the larger voltage.
True or false? A chemical cell made from two copper electrodes in an electrolyte produces a voltage.
False. The metals must be different — with no difference in reactivity the voltage is V.
True or false? A hydrogen–oxygen fuel cell produces carbon dioxide as well as water.
False. Water is the only product.
What is the overall balanced equation for the reaction in a hydrogen–oxygen fuel cell?
Give one strength of using a hydrogen–oxygen fuel cell rather than a rechargeable chemical cell to power a vehicle.
It gives a constant voltage for as long as hydrogen and oxygen are supplied.
(It also does not discharge when left unused, and contains no toxic substances to dispose of.)
Why are the electrodes of a hydrogen–oxygen fuel cell made from an unreactive metal such as platinum?
So they conduct electricity but are not used up — they do not react with the hydrogen, oxygen or water.