C4 - Chemical Changes Flashcards
What happens in a displacement reaction?
The more reactive metal will take the place of the less reactive metal in the compound.
What happens during oxidation or reduction?
- Oxidation is when oxygen is gained or
electrons are lost. - Reduction is when oxygen is lost or
electrons are gained.
O.I.L.R.I.G.
Bases and alkalis are chemicals that neutralise acids to form salts.
What is the difference between a base and an alkali?
A base is insoluble.
An alkali is a soluble base (dissolves in water)
A salt is a chemical made when acids are neutralised.
Name the type of salts made by these acids:
A - hydrochloric acid
B - sulfuric acid
C - nitric acid.
A - hydrochloric acid makes chloride
B - sulfuric acid makes sulfate
C - nitric acid makes nitrate
Why can some metals be extracted from their ores by heating them with carbon?
Metals can only be extracted from their ore by heating with carbon if they less reactive than carbon.
What is an ore?
A rock which contains enough metal to make it economically worthwhile to extract the metal from it.
What is the general equation for the reaction between a metal and an acid?
metal + acid → salt + hydrogen
What are the general equations for the reaction between an acid and a base and the reaction between an acid and an alkali?
Acid + base → salt + water
Acid + alkali → salt + water
What is the general equation for
the reaction between a metal oxide
and an acid?
Acid + metal oxide → salt + water
What is the general equation for the reaction between a metal carbonate and an acid?
acid + metal carbonate → salt + water + carbon dioxide
The positive and negative electrode are called the …
Cathode (Negative, -)
Anode (Positive, +)
What happens to positive ions at the negative electrode?
Positive ions will gain electrons at the negative electrode.
We call this reduction.
What happens to negative ions at the positive electrode?
Negative ions will lose electrons at
the positive electrode.
We call this oxidation.
Define the terms oxidation and reduction.
Oxidation- when a chemical loses 1 or
more electrons
Reduction- when a chemical gains 1 or
more electrons
In a solution of dissolved compounds, what ions are formed by the water?
Water molecules constantly break down into:
H+ ions
OH- ions
The equation for this is:
H20 ⇌ H+ + OH-
Write the order in which the
negative ions are discharged.
1 - Halide ions (Group 7)
2 - Hydroxide ions from water
which gives off oxygen gas
3 - Any other negative ions
Write the order in which the positive ions are discharged at the cathode.
Metals less reactive than hydrogen are made first.
Hydrogen gas is made if the metal is more reactive than hydrogen
Why is cryolite added to aluminium oxide when extracting aluminium?
Cryolite lowers the melting point of aluminium oxide (Al2O3).
This means that electrolysis can be carried out at lower temperatures, saving energy
