4. Chemical Changes Flashcards
What is produced when a metal reacts with oxygen?
metal + oxygen -> metal oxide
What is oxidation?
Gain of oxygen; loss of electrons
What happens to reactivity in terms of electrons?
The more easy it is to lose electrons, the more reactive the metal is
Mnemonic for the reactivity series?
Please send Charlie monkeys and cute zebras in tall long hard cages most securely guarded please
What is reduction?
Loss of oxygen & gain of electrons
What are the products of metal + acid?
Salt and hydrogen
What is OILRIG?
oxidation is loss, reduction is gain
What can metals more reactive than carbon be extracted using?
Electrolysis
What can metals less reactive than carbon be extracted using?
Reduction using carbon, coke or charcoal
What can elements less reactive than hydrogen be extracted using?
They don’t need extracting - they can occur native
What is displacement?
When a more reactive element takes the place of a less reactive element
How do you work out the relative atomic mass?
Multiply each mass number of each isotope by its % abundance
Add together
Divide by 100
What are bases?
Substances that react with acids and neutralise them (form a salt and water and sometimes carbon dioxide)
What is a base that is soluble in water also called?
An alkali
Are most bases insoluble?
Yes
What are acids?
Substances that react with water to release H+ ions
What are alkalis?
Bases that are soluble in water and react with water to release OH- ions
What some common acids?
Hydrochloric acid, sulphuric acid, nitric acid
What does acid + metal oxide give?
Acid + metal oxide -> salt + water
What does acid + metal hydroxide give?
Acid + metal hydroxide -> salt + water
What does acid + metal carbonate give?
Acid + metal carbonate -> salt + water + carbon dioxide
What does acid + ammonia give?
Acid + ammonia -> ammonium salt
What do acids react with water to give?
H+ ions
What do bases form when reacting with acids?
Salt and water (and sometimes carbon dioxide)
What do alkalis release when they react with water?
OH- ions
What are salts?
Ionic substances formed when acids react with bases
Does copper react with acid?
No
What is electrolysis?
The process where an ionic substance that is molten or dissolved is broken into elements using electricity
What does PANIC stand for?
Positive is anode. Negative is cathode
What charge is the anode?
Positive
What charge is the cathode?
Negative
What charge are anions?
Negative
What charge are cations?
Positive
What bonds do elements form at the anode?
Covalent
How do elements leave the system at the anode?
As gaseous diatomic molecules
What elements do bonds form at the cathode?
Metallic bonds with each other
What happens in terms of electrons at the cathode?
Each positive ion accepts electrons until it is charged
What happens to lost electrons at the anode?
They flow around the circuit to the negative electrode
Why do substances have to be in a solution or liquid during electrolysis?
So ions are free to move
What side of the equation do electrons appear on in oxidation?
The right hand side
What side of the equation do electrons appear on in reduction
Left hand side
Aluminium oxide -> aluminium + oxygen
Which are the cations and which are the anions?
Aluminium ions are cations and oxygen ions are anions
What are electrodes made from?
Graphite
What is used to dissolve aluminium oxide ore?
molten cryolite
Why does the anode need to be replaced regularly?
It heats up and then reacts so breaks down - CO2 will start to be produced
What happens to remains of disintegrated anodes?
Dismantled and new ones made out of them
What does discharges mean?
Lost charge
Which positive ions are discharged in a solution?
Ions lower than hydrogen in the reactivity series
What is formed when H+ ions are discharged in electrolysis?
H2
Which negative ions are discharged in a solution?
If the compound contains halide ions they are discharged. If not it’s OH-
What is formed when OH- ions are discharged during electrolysis?
O2
