Topic C4 - Chemical Change Flashcards
What does the lower PH numbers mean
That they are more acidic
What does the higher pH numbers mean
That they are more alkaline
How can you measure the pH of the solution
By using an indicator in the form of a dye that changes colour. For example universal indicator
Are using a pH probe attached to a pH meter
What is an acid
an acid is a substance that forms aqueous solution with a pH of less than seven. Acids form H+ ions in water
What is a base
Is a substance with a pH greater than seven
What is an alkali
Is a base that is dissolved in water to form a solution with a pH greater than seven. Alkalis form OH- ions in water
What is the Chemical formula of hydrochloric acid
HCl
What is the symbol equation for nitric acid
HNO3
What is the chemical formula for sulfuric acid
H2SO4
What is the chemical formula for phosphorus acid
H3PO4
What are common bases
Metal oxides
Metal carbonates
What are common alkalis
Ammonia
Metal hydroxide
What is the Chemical formula of ammonia
NH3
What is the salt created by sulphuric acid
Sulfates
What is the salt created by hydrochloric acid
Chloride
What is the salt created by nitric acid
Nitrate
What is the salt created by phosphoric acid
Phosphate
What are the products created by a
acid + reactive metal
Reaction
salt + hydrogen
What are the products created by a
acid + base/alkali
Reaction
salt + water
What are the products created by a
acid + carbonate
Reaction
salt + water + carbon dioxide
How do we know if an acid is strong
If the ions completely ionise in water
All acid particles dissociate to release H+ ions
How do we know if an acid is weak
If the ions does not fully ionise in solution
Only a small proportion of acid particles dissociate to release H+ ions
This is a reversible reaction
What is PH a measure of
The concentration of H+ ions in the solution
How do you workout concentration in terms of ph
For every decrease of one on the pH scale, the concentration of H+ ions increased by a factor of 10
What is the reactivity series
Is a list of metals in order of reactivity towards other substances
How are metal ores formed
By oxidation
How are metals extracted from its ores
By reduction
What is oxidation
The gain of oxygen
What is reduction
The loss of oxygen
How do you determine if a metal can be extracted by reduction with carbon
It is determined by the position of the metal in the reactivity series against carbon
What happens if the metal is higher than carbon in the reactivity series
It will have to be extracted using electrolysis which is explosive
How do you remember redox reactions
OIL RIG
Oxidisation is loss reduction is gain
In terms of electrons
What’s the meaning of electrolysis
Splitting up with electricity
What happens in electrolysis
1) During electrolysis and electric current is passed through an electrolyte. The ions move towards the electrodes
2) The positive ion (cation) in the electrolyte will move towards the cathode (the negative electrode) and gain electrons
3) The negative ion (anion) in the electrolyte will move towards the anode (the positive electrode) and lose electrons
What happened to cations in electrolysis
They are reduced (redox) to the element at the cathode
What happens to nonmetals in electrolysis
They are oxidised (redox) to the element at the anode
What happens in electrolysis of aqueous solutions
1) in aqueous solutions: there are ions from the ionic compound as well as hydrogen ions and hydroxide ions from water
2) at the cathode- if H+ ions and metal ions are present .
Hydrogen gas will be produced if the metal ions form an element that is more reactive than hydrogen
If it is less reactive than hydrogen a solid layer of the pure metal will be produced instead
3) At the anode - if OH- and halide ions (Cl-,Br- I-) are present:
Molecules of chlorine,bromine and iodine and will form
If no halide ions (Cl-,Br- I-) are present:
Then the OH- ions are discharged and oxygen will be formed
