topic 4 chemical changes Flashcards
What is oxidation/reduction?
oxidation – when a substance gains oxygen
Reduction – when a substance loses oxygen
how are unreactive metals found in earth?
In their natural state
how can metals less reactive than carbon be extracted?
Reduction with carbon. Carbon displaced the metal in a metal oxides – oxidised carbon oxides. Metals from the metal oxide gets reduced to the pure metal.
How are metals more reactive than carbon extracted?
Electrolysis
how are oxidation and reduction defined in terms of electron transfer
oxidation – loss of electrons
Reduction – gain of electrons
which metals in the reactivity series will react with an acid?
Those above hydrogen
what is the general equation for a neutralisation reaction?
base + acid ——> salt + water 
what is the general equation for the reaction between metal carbonate and an acid?
Metal carbonate + acid ——-> salt + water + carbon dioxide 
What is the general equation for the reaction between metal oxides and acids?
Metal oxide + acid ——> a salt + water 
What is a redox reaction?
Reaction were both oxidation and reduction occurs
Explain in terms of gain or loss of electrons which species has been oxidised and which species has been reduced when magnesium reacts with hydrochloric acid
magnesium has lost electrons and this has been oxidised
The hydrogen in HCL has gained electrons and this means it has been reduced
how is a soluble salt formed?
A-wrapped the excess acid with some insoluble chemical
B-filter off the leftovers
c-crystallised this product
what do acids and alkalis produce in aqueous solutions?
Acids produce hydrogen ions, alkalis produce hydroxide ions
What are bases, acids and alkalis?
bases are compounds that neutralise acids, acids produce hydrogen ions in acid solutions, alkalis a soluble bases – produce hydroxide ions in an aqueous solution
What is the pH scale and what does a pH of seven show?
The measure of acidity/alkalinity of a solution: neutral solution
State the general equation for a neutralisation reaction in a short, ionic form
H+ + OH- ——> H2O
What is a strong acid and a weak acid?
strong acid is completely ionised in aqueous solutions; weak acid is only partially ionised in aqueous solution
What happens to pH is concentration of H+ increases
The Ph decreases
what is concentrated acid and what is a diluted acid? Is this the same as a strong and weak acid?
Concentrated acid has more moles of acid per unit volume than a dilute
It is not the same concentration is not the same thing as strength of an acid
Strength refers to whether the acid is completely ionised in water or only partially
as the pH is decreased by one unit, what change is seen in the hydrogen ion concentration?
Increased by a factor of 10
what is electrolysis?
The passing of an electric current through ionic substance that are molten are in a solution to break them down into elements; ions discharged electro to produce these
What is an electrolyte?
The liquid/solution which conduct electricity
what is a cathode and what is a anode
cord is the negative electrode
anode is the positive electrode
What occurs at the cathode and what occurs at the anode during electrolysis
reduction occurs at the cathode
Oxidation occurs at the anode
In aqueous electrolysis, which element is discharge at the café? Oxygen is produced at the anode unless what
The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, in case this said metal is produced. Oxygen is produced at the anode unless the solution contains halide ions in which case halogen molecules are produced. 
how is aluminium manufactured? Why is it so expensive?
Aluminium is made through the electrolysis of aluminium oxide and croylite
Lots of energies needed to produce the current in electrolysis which makes this process expensive
why is Cryolite used in manufacturing of aluminium?
It lowers the melting point of aluminium oxide, reducing energy costs
