C4 Flashcards
What happens when metals react with oxygen?
Metal oxide
Oxidation is loss of … and gain of …
Loss of electrons and gain of oxygen
Reduction is gain of … and loss of …
Gain of electrons and loss of oxygen
What’s the order of the reactivity series?
potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen, copper, silver and gold
What is displacement of metals?
A more reactive metal can displace a less reactive metal from a compound.
Where is gold found and what’s it called?
In the ground, as an ore.
To get metals which are more reactive than carbon on their own, what do you do?
Electrolysis
To get metals which are less reactive than carbon on their own, what do you do?
Reduction with carbon
Equation for neutralisation
Acid + alkali = salt + water
Acids form what ions in water?
H+
Alkalis form what ions in water?
OH-
Equation for neutralisation with symbols
H+ + OH- –> H2O
Acid + metal =
salt + hydrogen
Metal + water =
metal hydroxide + hydrogen
Metal oxide + acid =
salt (metal sulfate etc) + water
Metal carbonate + acid =
salt, carbon dioxide and water
Making a salt practical
- Using metals, metal oxides, hydroxides or carbonates.- Heat acid to speed up reaction - The solid is added to the acid in excess - Solid is filtered- Put solution over Bunsen burner and gently heat - Leave overnight to crystallise.
pH scale
Measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
Titration practical
- Measure 25cm3 of sodium hydroxide (known) using a pipette to a conical flask.- Add an indicator to conical flask.- Place on a white tile to see colour change more clearly.- Add acid from burette and swirl
Equation for titration
Sulfuric acid + sodium hydroxide = sodium sulfate + water
Examples of strong acids
hydrochloric, nitric and sulfuric acids.
What does a strong acid do?
Completely ionise in an aqueous solution
Examples of weak acids
ethanoic, citric and carbonic acids.
What does a weak acid do?
Partially ionise in aqueous solutions
As the pH decreases by one unit, what happens?
The hydrogen ion concentration of the solution increases by a factor of 10
What’s an electrolyte?
When an ionic compound is melted or dissolved in water, the ions are free to move about within the liquid or solution. These liquids and solutions are able to conduct electricity.
Positively charged ions go where?
Move to the negative electrode, the cathode
Negative charged ions go where?
The positive electrode, the anode
Half equation for anode for chlorine
2Cl- → Cl2 + 2e-
Half equation for cathode for Copper(II) chloride (CuCl2)
Cu2+ + 2e-→ Cu
What does electrolysis mean?
Splitting up with electricty
Why can molten ionic compounds be split up with electrolysis?
Their ions can move freely
Why is electrolysis used?
To split up metals which are more reactive than carbon
Why is a mixture used as the electrolyte?
Because a mixture of positive and negative ions are needed
Disadvantage of electrolysis
Needs lots of energy so very expensive
What’s a cryolite?
Cryolite acts as a solvent and allows the electrolysis to take place at a lower temperature.
Why does using carbon at the anode mean the electrode needs to be completely replaced?
Carbon reacts with 02 so produces C02 which means the carbon is lost
Give an example of electrolysis
Aluminium oxide –> aluminium + oxygen
What happens if the metal is more reactive than hydrogen at the cathode?
At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen
What happens if there’s a halogen present at the anode?
At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced.
Practical 3 - investigate what happens when aqueous solutions are electrolysed using inert electrodes.
- Add the aqueous solution to the beaker 2. Add two graphite rods as the electrodes and connect this to a power pack or battery 3. Turn on the power pack or battery and allow electrolysis to take place 4. Record the results in a suitable table and repeat for another solution, checking the electrodes in between runs to see if any metal has been deposited 5. The gases produced can be collected in the test tubes to be tested later
Is the reaction at the cathode a reduction or oxidation?
During electrolysis, at the cathode (negative electrode), positively charged ions (metals) gain electrons and so the reactions are reductions
Is the reaction at the anode a reduction or oxidation?
At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations
