C5 - Chemical Changes Flashcards
Reaction of a metal and oxygen
- Metal + oxygen —> metal oxide
- This is an oxidation reaction (the metal is oxidised)
What is oxidation
- Where a substance gains oxygen
- OR when a substance loses electrons
OILRIG
What is reduction
- Where a substance loses oxygen
- OR where a substance gains electrons
OILRIG
What tests can be done to find the reactivity series
- Reactions with water
- Reactions with dilute acid
General reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Hydrogen
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
What does the reactivity of a metal depend on
- Its ability to lose electrons and form a positive ion
How are metals extracted from the earth
- Gold is unreactive so is found as a pure metal (native metal)
- Other metals are extracted using carbon (coal) as it is cheap and abundant (if less reactive than carbon)
- Electrolysis if they are more reactive than carbon
What is a displacement reaction with metals
Where a more reactive metals displaces a less reactive metal from an aqueous solution of one of its salts
What is an acid
a substance that forms H+ ions in aqueous solutions
all acids contain hydrogen
What is an alkali
A substance that contains OH- ions in aqueous solutions
Reaction of reactive metals with water
- Metal + water —> metal hydroxide + hydrogen
This is the case for potassium, sodium, lithium and calcium
Equation for neutralisation
OH-(aq) + H+(aq) —> H2O(l)
What is a base
- Metals oxides and metal hydroxides than can neutralise acids, produces a salt and water
Difference between an alkali and a base
- Alkalis are bases that can dissolved in water (soluble) to form aqueous solutions
Reaction of a metal and an acid and what salts do specific acids form
Acid + metal —> salt + hydrogen
* HCl forms chlorides
* Sulfuric acid forms sulphates
* Nitric acid forms nitrates
Reaction of an acid with a base or an alkali
acid + base/alkali —> salt + water
Reaction of metal carbonates with an acid
acid + metal carbonate —> salt + water + carbon dioxide
What is a strong acid and examples
- An acid that is fully ionised meaning every single molecule has split up into its ions
- This is shown by the reaction arrow being in one direction only
- Strong acids include sulfuric acid, nitric acid and hydrochloric acid
What is a weak acid with examples
- An acid that partially ionised in an aqueous solution.
- These are shown by a reversible reaction arrow
- Weak acids include carbonic acid, ethanoic acid and citric acid
How to detect pH
- Universal indicator - colour
- Electronic pH probes - numerical value
Rule of the pH scale
As the pH decreases by one unit, the concentration of hydrogen ions increases by ten times (1 order of magnitude)
What is the concentration of an acid and the difeference between dilute and concentrated
- The amount of acid molecules in a set volume
- Dilute means less molecules
- Concentrated means more
Where does the metal ion come from in a salt
- The pure metal itself
- Metal oxide
- Metal hydroxide
- Metal carbonate
