C4 Flashcards
What is an electrode made of?
Carbon/graphite
What is an electrolyte?
An ionic compound in a molten or aqueous state
What is electrolysis?
The breakdown of ionic compounds using electricity.
Give the general ionic equation for neutralisation.
H+(aq) + OH-(aq) –> H20(l)
Detail the steps of producing soluble copper salts by neutralising sulfuric acid with copper (II) oxide/carbonate.
- Pour 20ml of 0.5mol/dm^3 sulfuric acid into a 100ml beaker
- If using copper oxide, heat the solution to near-boiling with a Bunsen burner.
- Add the copper compound until excess into the acid, swirling so that it all reacts.
- Filter your copper sulfate solution to remove excess copper oxide/carbonate
- Pour the solution into an evaporating basin until half has evaporated.
- With tongs, pour the solution into a crystallising dish and leave it in a warm place to complete the crystallising process
Copper oxide + sulfuric acid –> what?
copper sulfate + water
Copper carbonate + sulfuric acid –> what?
copper sulfate + water + carbon dioxide
What is a weak acid?
Releases a small proportion of available hydrogen ions into aqueous solution (partially ionised). (PH 4-6)
What is a strong acid?
Releases all hydrogen ions in aqueous solution (ionises completely). (PH 0-3)
What is the use of cryolite in the extraction of aluminium oxide?
Lowers the melting point, reducing energy costs
What is a base?
An insoluble substance that neutralises acids
In the electrolysis of aqueous solutions, what is produced at the cathode?
Either hydrogen or the metal element is produced; whichever is LESS reactive.
In the electrolysis of aqueous solutions, what is discharged at the anode to produce what?
If halide ions are present, they are discharged and the halogen is produced. If not, the hydroxide ion from the water is discharged and oxygen + water are produced.
What material are electrodes made of?
Carbon
What is brine?
Sodium chloride solution
At the cathode, will metal ions be reduced or oxidised?
Reduced; they gain electrons
How do you calculate percentage yield?
(Mass of products / expected mass) x 100
Why may you need to replace the anodes frequently in electrolysis?
The oxygen formed reacts with the carbon composing the anode.
Which two ions are always present in aqueous electrolysis and why?
H+ and OH-, from the water
Name one weak and strong acid
Weak: Ethanoic acid
Strong: Hydrochloric acid
or anything else correct
Describe the method for making crystals of potassium chloride from potassium hydroxide solution.
You should describe how you obtain the correct amount of HCl to neutralise the NaOH and how you will get crystals of potassium chloride. Also describe apparatus used.
Pour 20ml of potassium hydroxide into a conical flask on a white tile with 3 drops of methyl orange (added with a pipette). Fill a burette with hydrochloric acid and run it into the conical flask slowly (always swirling the flask) until the solution turns from orange to yellow. Towards the end point, add the HCl dropwise. Measure (from the meniscus) and record the volume of acid used to neutralise the potassium hydroxide.
With a clean conical flask, measure another 20ml of potassium hydroxide (with no methyl orange) and add the recorded volume of acid to neutralise it. Pour the solution into an evaporating basin and heat to evaporate half of it. Pour the heated solution into a crystallising dish and leave it to crystallise for a week.
Acid + alkali –> what?
Salt + water
Acid + metal –> what?
Salt + hydrogen
Detail the steps of writing an ionic equation.
- Split everything aqueous into its ions (leave everything else)
- Remove every ion that is the exact same in the products and reactants
- Piece the rest together
Is the cathode negatively or positively charged?
Negative, because cat eyes glow at night which is kinda like a negative time
Is the anode negatively or positively charged?
Positive, because A is a positive grade
On the reactivity series, which 3 metals are less reactive than hydrogen?
Copper, silver, gold
Explain how oxygen is produced in aqueous electrolysis
A small proportion of water molecules dissociate into hydroxide and hydrogen ions. OH- ion are attracted to the anode, losing electrons (being oxidised) and forming oxygen gas.
2H2O(l) → 2H2(g) + O2(g)
