1
Q
Please Send Lions Cats Monkeys And Cute Zebras Into Hot Countries. Signed, Gordon.
A
Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium, (Carbon), Zinc, Iron, (Hydrogen), Copper, Silver, Gold
2
Q
What happens if a metal looses ions more easily?
A
It’s more reactive
3
Q
Reactivity with water and acids?
A
4
Q
How do highly reactive metals (K, Na, Li) react with water and acid? What do they produce?
A
- most vigorously
- hydrogen gas
- can even be explosive
5
Q
How do Mg and Ca react with water?
A
Less vigorously
6
Q
how do Zn and Fe react with water and acid?
A
- dont react with water. React with steam
- slow reaction (very) with acids
7
Q
How does copper react with water/ acids?
A
It doesn’t
8
Q
What is produced when a metal reacts with water?
A
Metal hydroxide + hydrogen
9
Q
What is produced when a metal reacts reacts with acid?
A
Metal salt + hydrogen
10
Q
Why do we need to extract pure metals from ores?
A
- metal reacts with oxygen to form metal oxide
- most metals in environment are found in metal oxides in ores
- need to extract pure metal for use via chemical reactions
11
Q
Oxidation? Reduction?
A
- Loss of electrons, gaining oxygen
- gaining electrons, losing oxygen
12
Q
What type of reaction is extracting metals from oxides?
A
Reduction
13
Q
What are the three main extraction techniques?
A
- more reactive than carbon: electrolysis
- less reactive than carbon: reduction using carbon
14
Q
What metal isn’t needed to be extracted?
A
Gold- unreactive
15
Q
What happens in reduction with carbon to separate metals from their ores?
A
- carbon is more reactive so displaces less reactive metal
- forms carbon dioxide
16
Q
What are redox reactions?
A
When oxidation and reduction occur in the same reaction
17
Q
What is displacement?
A
- more reactive metal replaces less reactive one
- a redox reaction
18
Q
Where do we put the electrons in reduction and oxidation half equations?
A
- reduction: gain —> placed on reactants side(left)
- oxidation:loss —> placed on product side (right)
- (number of electrons gained/ lost)e
19
Q
What happens to acids in solutions?
A
hey release their hydrogen H+ ions
20
Q
What happens to alkalis in solution?
A
Release hydroxide ions OH-.
21
Q
What is a wide range indicator?
A
- example can be a universal indicator
- show a variety of colours based on pH of solution
22
Q
benefit of immersing pH probes in solutions?
A
Precise measurement
23
Q
What is neutralisation reaction?
A
-When an acid and a base react to form water and salt.
- involves transfer of H+ ions from the acid to OH- ions of alkali forming H2O
24
Q
Examples of bases?
A
- metal hydroxides
- metal carbonates (also produce CO2)
- metal oxides
25
What does it mean acids ionise when dissolved in water?
- molecules of acid break up
- into their ions
- so realise H+ ions
26
What are strong acids? Give examples?
- acids that fully ionise and release all of their H+ ions in water
- higher concentration of H+ ions results in lower pH
- nitric, sulphuric, hydrochloric
27
Examples of weak acids?
- partially ionise —> lower concentration of H+ ions so higher pH
- ethanoic, citric, carbonic
28
Whats the relationship between H+ ion concentration and pH?
- increase H+ ion concentration by factor of 10 times
- pH decreases by 1
29
Whats the difference between concentration and strength of acids?
- concentration: number of acid molecules in a given volume (dilute/ concentrated)
- strength: degree of ionisation in water
30
What type of bases are alkalis?
Soluble in water (metal hydroxides)
31
Salts formed based on acid?
- chloride (cl-)
- nitric (NO3) -
- sulfate (SO4)2-
32
How do we make salts? Example?
- soluble salts made from reacting insoluble base with an acid
- e.g. lithium chloride: lithium oxide/ carbonate and HCl (group 1 metals in metal hydroxidedes makes them highly soluble)
33
Method for producing lithium chloride?
1) gently heat acid using Bunsen burner
2) add lithium oxide little by little to the acid whilst swirling it.
3) continue adding lithium oxide until it won’t dissolve anymore (its in excess and settles at the bottom of beaker without reacting)
4) filter out undissolved lithium oxide via filtration
5) gently heat the solution using a water bath. That increases the concentration solution. Once it has saturated, allow it to cool.
6) salt will crystallise and can be collected via filtration.
34
What are bases?
Substances that neutralise acids.
35
What do traction help us find out?
- how much acid needed to neutralise a base
- can find out unknown concentration using known
36
Why do we use narrow range indicators in titrations?
- because they innately show colour change when neutralisation occurs
37
What colour is phenolphtalein in acids and alkalis?
- acids: colourless
- alkali: pink
38
How to find the concentration of sodium hydroxide when reacting sulfric acid with sodium hydroxide?
1) measure 25cm3 using a pippette of sodium hydroxide into a conical flask. Add few drops of phenolphthalein and swirl.
2) fill burette with sulphuric acid using a funnel and record initial reading of the in the burette (always read from bottom of meniscus).
4) add acid from burette to flask whilst swirling flask.
5) add acid drop by drop
6) stop acid immediately when indicator changes colour (pink to colourless) + record final volume.
7) repeat and calculate mean volume of acid + unknown concentration.
39
What is electrolysis?
Using electricity to break up ionic compounds
40
What are the different parts in electrolysis?
- electrolyte: ionic compound being separated (molten or aqueous)
- electrode: to pass electricity through electrolyte (a circuit with battery connected to two carbon electrolytes)
41
What are anode and cathode?
- anode: + electrode
- cathode: - electrode
42
Describe the electrolysis process?
- positively charged ions move to cathode (-) where they get discharged turning into atoms of that element
- negatively charged ions move to anode (-) where they get discharged and turn into atoms of that element
43
What reactions occur at each electrode?
- Anode: loose electrons (oxidation)
- Cathode: gain electrons (reduction)
- at the end both form neutral atoms
44
What are the products formed from molten electrolytes?
The elements present in the electrolyte
45
How to write ionic half equations?
- put ion on the left and atom on the right
- check if the atom is diatomic and balance the equation
- add electrons to make charges balances (differs where you put the electron in anode and cathode)
2Cl- —> Cl2 + 2e -
46
Why is extracting metals with electrolysis expensive?
- metals more reactive than carbon need to be extracted via electrolysis
- large amount of energy to melt the metal ores so they’re molten (ions free to move)
- electricity needed for electrolysis
- all can be very expensive
47
How do we extract aluminium from its ore?
1) mix aluminium oxide with cryolite to lower melting point (less energy needed to melt it so cheaper process)
2) melt aluminium oxide so it’s molten (the ions will be Al3+ and O2-)
3) usually more than one anode submerges and cathode lines inside of container
4) aluminium ion attracted to cathode and oxygen ions attracted to anode
5) aluminium gets reduced and oxygen ions get oxidised
6) molten aluminium collected at bottom and oxygen bubbles given off at anode
48
Why does molten liquid aluminium flow to bottom of container?
Due to high temperature
49
Why do graphite anodes need to be replaced?
In the electrolysis of aluminium oxide the carbon from graphite ANODE and oxygen ions form carbon dioxide and is given off so the electrode wears away.
- this happens due to high temperatures allowing carbon and oxygen to bond as they’re inert
50
Why are the products formed in aqueous electrolytes not always the elects in the compound?
Because there are more than two different ions present
51
What can happen to water in aqueous solutions?
It can partially ionise to realise H+ and OH- ions so electrolytes can contain ions from the compound and these ions
52
Discharge rules for aqueous electrolytes?
- cathode: less reactive (positive ions- element vs hydrogen) element is produced
- anode: if halogen is present, that is produced. If not then oxygen is produced (hydroxide ions travel to the anode and discharged to form oxygen gas (4OH- —> O2 + 2H2O + 4e-) (why?)
53
Chlorine gas
54
Required practical: electrolysis using inert electrodes method?
1) choose an electrolyte
2) pour sample of electrolyte into beaker
3) immerse two inert graphite electrodes into solution and place in inverted test tube over each electrode.
4) pass current through the electrolytes and collect gasses in the inverted test tubes/ measuring cylinders
5) test for the gas using chemical tests
Chemistry
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