Unit 4- Chemical Changes Flashcards
On the Ph scale what number are acids and what colour are they
0-6
Red to yellow
On the Ph scale what number is neutral and what colours is it
7 - green
On Ph scale what number and colour is alkalis
8-14
Blue to purple
How do you measure Ph of a solution
Use an indicator will change colour depending on whether it’s above or below a certain Ph.
What is the relation between acid and bases
They neutralise each other
What is a base
Substance that will react with an acid to form a salt
Equipment you will find in a titration experiment
Burette, conical flask with methyl orange, pipette
What colour will phenolphthalein turn
Pink in alkali
Colourless in acid
What colour will methyl orange turn
Red in acid
Yellow in alkali
What colour will litmus turn
Red in acid
Blue in alkali
What does a acid and metal oxide make
Salt and water
What does salt and metal hydroxide make
Salt and water
What do acids produce in water
Protons
What type of reaction the ionisation of a weak acid
Reversible, equilibrium lies go the left
What happens with weak acids in solution
Don’t fully ionise, only small portion release H ions
What happens with strong acids in water
Ionise completely, dissociate to realise H ions
For metals how is their reactivity determined
How easily they lose electrons forming positive ions
What is the relativity series in order
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
What does acid and metal make
Salt and hydrogen
What is oxidation
gain of oxygen or loss of hydrogen
Negatively charged ions lose electrons at the Anode
What is reduction
Positively charged ions gain electrons at the cathode
loss of oxygen or gain or hydrogen
What is a redox reaction
a reaction in which both oxidation and reduction occur
What is electrolysis
Splitting up compounds with electricity to form elements
What is an electrolyte
A liquid or solution that conduct electricity
What does electrolysis of molton ionic solids form
An element
What is the positive electrode
Anode
What is the negative electrode
Cathode
Which electrode does positive metals go
Reduced at the cathode
Which electrode do non metal ions go
Oxidised at the anode
Why can ionic compound not undergo electrolysis
Because the ions are in fixed positions and can’t move
Why is hydrogen chloride a gas at room temperature
Weak intermolecular forces
What is an intermolecular force
Strong attractive force
What is activation energy
Minimum amount of energy required for a chemical reaction to occur
What does bond energy mean
Energy needed to break mole of particular bond
Differences between the nuclear and plum pudding model
Plum pudding there is no empty spaces
Electrons orbit the nucleus in nuclear model
Mass of atom is in centre in plum pudding / evenly distributed in nuclear model
Why does graphite conduct electricity
Each carbon atom forms 3 covalent bond one atom is delocalised and these electrons carry charge through graphite
Explain why hydrogen chloride is a gas at room temperature
Hydrogen chloride is simple molecular so has weak intermolecular forces therefore requiring little energy to overcome
Explain why you would not expect titanium chloride to be a liquid at room temp
Titanium chloride is ionic and metal chlorides have high melting points because they have strong electrostatic forces between ions
Explain why an acid can be both strong and dilute
Strong because completely ionised
Dilute because small amount of acid per unit volume
Why should you use a polystyrene cup rather than a glass beaker
Polystyrene is a better insulator so reduced energy exchange with surroundings
What two substances out of diamond, magnesium, polythene, sodium chloride and water have intermolecular forces
Water and polyethene
What electrode do metals go to
Cathode
What electrode does hydrogen go to
Cathode
What does inert mean
Unreactive
What element is used to reduce metal oxides and make pure metals
Carbon
Acid + metal —>
Salt + hydrogen
Acid + metal carbonate —>
Salt + water + carbon dioxide
What do aqueous solutions of alkali contain
OH ions
what happens to the ions in an ionic compound when melted or dissolved in water
The ions become free to move allowing them to conduct electricity
What ions are discharged to produce oxygen at the positive electrode
Hydroxide ions (H plus and OH minus)
Advantages of hydrogen fuel cells
No toxic chemicals to dispose at the end of cell life
No loss of efficiency over time
You can travel further before refuelling
Disadvantages of extraction of metals using electrolysis
Very expensive because it requires a lot of energy and electricity
When extracting metals when should you use electrolysis
If metal is more reactive than carbon
What can metals be mixed with to lower melting point so they are ready for process of electrolysis
Cryolite, making it easier to melt and reducing the energy required for the electrolysis process
Equation linking moles
Concentration and volume
Moles =concentration x volume
What is a neutralisation reaction
Acid and alkali react together
What are the rules for electrolysis
- The less reactive negative ion will be reduced at the cathode while the more reactive stays in the solution
- If there is a halide ion (fluoride, bromide chloride) they are always oxidised at the anode (halogen gases are diatomic so remember for half equations ), if not oxygen is produced
- the other ions stay in the solution so if sodium and hydroxide ions are left they makes sodium hydroxide
What is the reactivity series in order
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold platinum
What is produced at anode and cathode and give half equations for electrolysis of sodium chloride
Cathode = hydrogen reduced
2H+ + 2e- —> H2
Anode = chloride oxidised
2Cl—-> Cl2 + 2e-
Sodium hydroxide left in solution
What is produced at anode and cathode and give half equations for electrolysis of copper sulfate
Cathode = copper ions reduced
Cu2+ +2e- —> Cu
Anode = oxygen is oxidised
4OH- —> O2 + 2H2O + 4 e-
Sulphuric acid left in solution
What is produced at anode and cathode in electrolysis of molten compound aluminium oxide also give half equations
Cathode = aluminium reduced
Al3+ + 3e- —> Al
Anode = oxygen is oxidised
2O2- —> O2 +4e-
