C4 Flashcards
Metal + oxygen is what and what reaction takes place?
Metal oxide, oxidation reaction
What happens in an oxidation reaction?
Oxygen is gained and electrons are lost.
What happens in a reduction reaction?
Oxygen is lost and electrons are gained.
G1 metal + water is what
Metal hydroxide (alkali) + hydrogen
What metals do not react with water at room temperature?
Magnesium, zinc, iron, copper
What metals react rapidly and quite rapidly with water at room temperature?
Potassium, sodium, lithium and (calcium reacts quite rapidly).
What does the reactivity of a metal depend on?
Its ability to lose electrons and from a positive ion.
Half equation for oxidation for magnesium
Mg -> Mg2+ + 2e-
Half equation for reduction for sulfur
S + 2e- -> S2-
What ions do acids produce in aqueous solutions?
Hydrogen ions (H+)
Acid + base is what and what type of reaction is it?
Salt + water, neutralisation reaction
What are bases usually?
Metal oxides or metal hydroxides
Define alkali
A base that is soluble in water.
What ions do alkalis produce in aqueous solutions?
Hydroxide ions (OH-)
H+ + OH- is what
H2O - water
Metal + water is what and what reaction is it?
Salt + hydrogen, displacement reaction (metal has displaced the hydrogen)
In a metal + acid reaction, what is oxidised and what is reduced?
Metals are oxidised and acid is reduced
Define base
Chemicals which can neutralise acids and produce a salt and water.
Acid + metal carbonate is what?
Salt + water + carbon dioxide
How to make soluble salts (practical)?
- Warm the dilute acid using a Bunsen burner, then turn it off.
- Add the insoluble base to the acid a bit at a time, until no more reacts (the base is in excess).
The acid will be neutralised when the excess solid will just sink to the bottom of the flask. - Filter out the excess solid to get the salt solution.
- To get pure, solid crystals of the salt, leave the solution for 24 hours in a cool place.
Crystals should form, which can be filtered out the solution and then dried using a paper towel - crystallisation.
What happens to acid molecules in solution?
Acid molecules ionise (split) and release H+.
How do strong acids ionise in aqeous solutions?
Fully ionise is aqueous solutions.
3 strong acids
Hydrochloric / sulfuric / nitric acid
How do weak acids ionise in aqeous solutions?
Partially ionise in aqueous solutions (reversible reaction).
3 weak acids
Carbonic / ethanoic / citric acid
Why do strong acids have a lower pH than weak acids?
Strong acids fully ionise creating a greater concentration of hydrogen ions than weak acids.
How many times greater is the concentration of H+ in pH 1 than 2?
10x greater (one order of magnitude)
Define the concentration of an acid
The amount of acid molecules in a given volume of solution. A dilute acid will have fewer acid molecules in a given volume than a concentrated acid even if the strength is the same.
How to make an ionic compound conduct electricity?
Melt it or dissolve in water - the forces of attraction are broken and ions are free to move.
What is the negative and positive electrode called and what are they covered with?
Cathode - colvered with electrons, anode - lack of electrons
Which electrode are the positive ions attracted to what reaction is it?
The negative electrode - cathode, reduction reaction.
Which electrode are the negative ions attracted to what reaction is it?
The positive electrode - anode, oxidation reaction.
Metals that are more reactive than carbon are extracted using what?
Electrolysis
Metals that are less reactive than carbon are extracted using what?
Carbon
How is electrolysis of aluminium oxide done?
- Aluminium oxide is mixed with cryolite with lowers the melting point - reduces the amount of energy needed and saves money. 2. The cathode attracts the positive aluminium ions and the negative oxide ions attracts to the anode.
Why must the anode be replaced regularly?
The oxygen molecules produced at the anode reach with the graphite (carbon), forming carbon dioxide gas. C + O2 -> CO2
Why is electrolysis expensive?
Melting the compounds requires a great deal of energy and a lot of energy is required to produce the electric current.
In the electrolysis of aqueous solutions, what is produced at the cathode if the metal is more reactive then hydrogen? What is the half equation?
Hydrogen, 2H+ + 2e- -> H2
In the electrolysis of aqueous solutions, what is produced at the cathode if the metal is less reactive then hydrogen? What is the half equation?
Pure metal, Cu2+ + 2e- -> Cu
In the electrolysis of aqueous solutions, what is produced at the anode if a halide ion is present? What is the half equation?
Halogen gas, Cl- -> Cl2 + 2e-
In the electrolysis of aqueous solutions, what is produced at the anode if a halide ion is not present? What is the half equation?
Oxygen, 4OH- - 4E- -> 2H2O + O2
Test for chlorine gas
Bleaches damp blue litmus paper
Test for hydrogen gas
Produces a squeaky pop near a lit splint
Metal + acid is what
Salt and hydrogen
