Section 4 - Pgs 50-58 Flashcards
1
Q
What numbers does the pH scale go from and to?
A
0 to 14
2
Q
What is the neutral pH?
A
7
3
Q
What is the strongest possible acid pH?
A
O
4
Q
What is the strongest possible alkali pH?
A
14
5
Q
Give an example of a strong acid.
A
Car battery acid
6
Q
Give an example of a weak acid.
A
Vinegar, Lemon juice
7
Q
Give an example of a strong alkali.
A
Caustic soda, Bleach
8
Q
Give an example of a weak alkali.
A
Washing up liquid
9
Q
What is an indicator?
A
A dye that changes colour depending onthe pH it is in.
10
Q
Give 4 examples of indicators.
A
- Universal indicator
- Litmus paper
- Phenolphthalein
- Methyl orange
11
Q
Describe the colour of universal indicator in acidic, neutral and alkaline conditions.
A
Acidic: Red
Neutral: Green
Alkaline: Blue
12
Q
Describe the colour of litmus paper in acidic, neutral and alkaline conditions.
A
Acidic: Red
Neutral: Purple
Alkaline: Blue
13
Q
Describe the colour of phenolphthalein in acidic and alkaline conditions.
A
Acidic: Colourless
Alkaline: Pink
14
Q
Describe the colour of methyl orange in acidic and alkaline conditions.
A
Acidic: Red
Alkaline: Yellow
15
Q
What is an acid a source of?
A
H+ ions
16
Q
What is an alkali a source of?
A
OH- ions
17
Q
What is the differnce between alkalis and bases?
A
Alkalis are soluble bases
18
Q
Acid + Base ->
A
Acid + Base -> Salt + Water
19
Q
Give a half-equation for a neutralisation reaction.
A
H+ + OH- -> H2O
20
Q
Acid + Metal oxide ->
A
Acid + Metal oxide -> Salt + Water
21
Q
Acid + Metal carbonate ->
A
Acid + Metal carbonate -> Salt + Water + Carbon dioxide
22
Q
E.g. Hydrochloric acid + Copper oxide ->
A
Hydrochloric acid + Copper oxide -> Copper chloride + Water
23
Q
E.g. Nitric acid + Calium carbonate ->
A
Nitric acid + Calium carbonate -> Calcium nitrate + Water + Carbon dioxide
24
Q
What is the chemical formula for hydrochloric acid?
A
HCl
25
What is the chemical formula for sulphuric acid?
H2SO4
26
What is the chemical formula for nitric acid?
HNO3
27
What is the chemical formula for phosphoric acid?
H3PO4
28
What is the chemical formula for ethanoic acid?
C2H4O3
29
What is a salt?
A substance that is formed when the hydrogen in an acid is replaced by a metal.
30
What are the general rules for soluble salts?
* All nitrates
* All sodium potassium, sodium and ammonium salts
* Most chlorides (except AgCl, PbCl2)
* Most sulphates (except CaSO4, BaSO4, PbSO4)
* Most carbonates are insoluble
31
What are the solubility rules about nitrates?
All are soluble
32
What are the solubility rules about sodium, potassium and ammonium salts?
All are soluble
33
What are the solubility rules about chlorides?
Most are soluble except:
| AgCl, PbCl2
34
What are the solubility rules about carbonates?
Most are insoluble (except group 1)
35
What are the solubility rules about sulphates?
Most are soluble except:
| CaSO4, BaSO4, PbSO4
36
What are the exceptions to the solubility rules?
* Silver chloride and lead chloride insoluble
| * Barium sulphate, calcium sulphate and lead sulphate insoluble
37
Why are two different methods required for making soluble salts?
- Some salts can be made by adding an excess of an insoluble base to an acid.
- However, some bases are soluble (e.g. sodium, potassium and ammonium compounds) so it is impossible to tell when an excess has been added because the base dissolves. Titration has to be done instead.
38
Why can't sodium, potassium or ammonium salts be made using the 'adding an excess of solid and then filtering it off' method?
That method requires an insoluble base, and potassium, sodium and ammonium salts and compounds are always soluble.
39
What method can be used to make a soluble salt which is not a sodium, potassium or ammonium salt?
Adding an excess of a base to an acid and then filtering off the excess base:
• Get the correct metal oxide, carbonate or hydroxide, making sure it is insoluble
• Get the correct acid
• Keep adding the insoluble base to the acid until the reaction stops and there is an excess at the bottom of the acid
• Filter off this excess, heat the remaining solution for some time and evaporate it to get crystals
40
What method can be used to make a soluble sodium, potassium or ammonium salt?
Titration - This is used to find out the precise amount of acid needed to neutralise the right alkali:
• Get the required amount of the sodium, potassium or ammonium solution
• Add a few drops of an indicator such as methyl orange
• Fill a burette with the acid and start adding it to alkali until the colour of the indicator shows that it has been neutralised
• Record the amount of acid used
• Repeat the experiment without indicator (it would colour the crystals). This time you know how much acid to use with the indicator.
• Heat and evaporate half of the new solution
• Leave to evaporate and crystallise
41
Describe the process of formation of an insoluble salt.
* Mix two solutions - one with the correct positive and one with the negative ion
* Remember each of the first solutions must contain a soluble compound, or it can't be a solution
* The reaction should form a solution and precipitate
* Filter this to get the precipitate - this is the salt
42
What is the process of making an insoluble salt called?
A precipitation reaction
43
What is titration used for?
Finding out how much acid is needed to neutralise a quantity of an alkali.
44
Describe the process of titration.
* Using a pipette, add some alkali to a concial flask
* Add a few drops of indicator
* Fill a burette with acid
* Add acid to the alkali a bit at a time, swirling regularly
* Wait until the indicator changes colour
* Record the volume of acid used
* Repeat several times and take an average
45
In titrations, how can the number of moles and concentration of a substance be worked out?
1. Work out the moles of the substance you are given volume and concentration for (Moles = Conc x Vol)
2. Use the equation to find the ratio between the two substances
3. Thus, work out the number of moles of the unknown substance
4. Work out the concentration of the unknown substance (Moles = Conc x Vol)
46
Give an example of a very slow reaction.
Rusting of iron
47
Give an example of a moderate speed reaction.
Metal reacting with acid to produce slow stream of bubbles
48
Give an example of a very fast reaction.
An explosion
49
What four factors affect the rate of a reaction?
1. Temperature
2. Concentration (or pressure for gases)
3. Catalyst
4. Size of particles (or SA)
50
What is the eqation for rate of reaction?
Rate of reaction = Amount of reactant used or amount of product formed / Time
51
What are the 3 ways in which the rate of a reaction can be measured?
1. Precipitation
2. Change in mass
3. Volume of gas given off
52
How can precipitation be used to measure rate of reaction?
1. If the solution is clear, a piece of paper with a cross can be put under the flask
2. Measure the time until the preciptate clouds the flask and the cross can no longer be seen
53
How can change in mass be used to measure rate of reaction?
1. If the reaction produces gas, the change in mass of the reactants can be monitored
2. The rate at which the mass decreases is the rate of reaction
54
How can volume of gas given off be used to measure rate of reaction?
1. Reaction flask is connected to gas syringe
| 2. The more gas is given off in a given time, the faster the reaction
55
Which experiment is used to investigate the effect of surface area on rate of reaction?
Reaction of hydrochloric acid with marble chips to produce CO2 gas.
56
Describe how the reaction between HCl and marble chips can be used to investigate the effect of surface area on rate of reaction.
1. Measure set mass of large marble chips and HCl
2. Measure the volume of gas produced at regular intervals during the reaction
3. Repeat with the same mass of marble chips, but in smaller pieces
4. Plot a graph of time (x axis) against volume of gas (y axis)
57
Remember to revise rate of reaction graphs.
Pgs 54-57 of revision guide
58
Which experiment is used to investigate the effect of concentration on rate of reaction?
Reaction of magnesium with dilute HCl to produce hydrogen.
59
Describe how the reaction between magnesium and dilute HCl can be used to investigate the effect of concentration on rate of reaction.
1. Measure set mass of magnesium and HCl
2. Measure mass of reactants at regular intervals
3. Repeat with the same mass of magnesium, but more concentrated HCl
4. Plot a graph of time (x axis) against loss in mass (y axis)
60
Which experiment is used to investigate the effect of temperature on rate of reaction?
Reaction of sodium thiosulphate with HCl to produce a cloudy precipitate of sulphur.
61
Describe how the reaction between sodium thiosulphate and HCl can be used to investigate the effect of temperature on rate of reaction.
1. Prepare an set volume of each solution -> Both are clear
2. Use a water bath to heat the reactants to a set temperature before mixing them above a black cross
3. Time how long it takes for the black cross to disappear due to the precipitate
4. Repeat with same volumes of reactants at different
5. No graph to plot
62
Which experiment is used to investigate the effect of a catalyst on rate of reaction?
Decomposition of hydrogen peroxide to produce oxygen gas.
63
Describe how thedecomposition of hydrogen peroxide can be used to investigate the effect of a catalyst on rate of reaction.
1. Set volume of H2O2 is prepared
2. The volume of gas produced is measured at regular intervals
3. Repeat the experiment with same volume of H2O2, but using a different catalyst each time
4. Catalysts: Manganese(IV) oxide, potato peel, blood
5. Plot graph of time (x axis) against volume of gas (y axis)
64
What is collision theory?
The idea that particles have to collide in order to react and that they have to do it hard enough. The rate of reaction depends on how often this happens.
65
In terms of collision theory, what has to be done in order to increase the rate of reaction?
The number of successful collisions per second has to be increased.
66
How does a higher temperature increase rate of reaction in terms of collision theory?
* The particles have more energy and move quicker
| * This increases the number of collisions and more of these happen with sufficient energy
67
How does a higher concentration / pressure increase rate of reaction in terms of collision theory?
* In a solution, there are more reactant particles between water molecules, making a collision more likely
* In a gas, the particles are more squashed up so they collide more frequently
68
How does a larger surface area increase rate of reaction in terms of collision theory?
• The particles in the solution have a larger surface area to collide into, making collisions more frequent
69
How does a catalyst increase rate of reaction in terms of collision theory?
* Increase the number of successful collisions by lowering the activation energy
* This is done by providng an alternative reaction pathway with a lower activation energy
70
In terms of collision theory, what is the only way of causing FASTEr collisions?
Increasing temperature
71
What is activation energy?
The energy required to break the initial bonds in the reactants, allowing a reaction to happen.
