Topic 3:Acids And Alkalis Flashcards
(93 cards)
1
Q
What is the chemical symbol and charge for sulphate ion
A
SO4 , 2-
2
Q
What is the chemical symbol and charge for carbonate ion
A
CO3 , 2-
3
Q
What is the chemical symbol and charge for nitrate ion
A
NO3 , 1-
4
Q
What is the chemical symbol and charge for hydroxide ion
A
OH , 1-
5
Q
What is the chemical symbol and charge for phosphate ion
A
PO4 , 3-
6
Q
What is the chemical symbol and charge for ammonium ion
A
NH4 , 1+
7
Q
What are the 6 polyatomic ions?
A
Sulphate Carbonate Phosphate Hydroxide Nitrate Ammonium
8
Q
What rage of number is the pH of acids?
A
Less than 7
9
Q
What rage of numbers is the pH of alkalis?
A
More than 7
10
Q
What are acids formed from?
A
Compounds that contain hydrogen
11
Q
What happens when the compound is dissolved in water?
A
They split into hydrogen ions
12
Q
What is the concentration?
A
Amount of substance per unit volume of solvent
13
Q
What does high pH mean?
A
Low concentration
14
Q
What is the end point?
A
The points at which the indicator changes colour
15
Q
What are indicators?
A
Substances that change colour at a certain pH
16
Q
What is the equation for concentration?
A
Concentration = mass/volume
17
Q
What is concentration measured in?
A
g/dm3
18
Q
What is volume measure in?
A
Dm3
19
Q
What happens as the concentration is increased by a factor of 10?
A
The pH goes down by 1
20
Q
How are strong acids formed?
A
From compounds that split up (dissociate) completely into ions
21
Q
3 examples of strong acids
A
Hydrochloric acid
Sulphuric acid
Nitric acid
22
Q
What happens to weak acids?
A
They do not fully dissociate, only some molecule split up to release hydrogen ions
23
Q
1 example of a weak acid
A
Ethanoic acid
24
Q
What are bases?
A
Metal oxides and hydroxides, any substance that reacts with an acid to form a salt and water only
25
What can bases do?
Neutralise acids
26
Which bases are soluble?
Only the alkali bases, the rest are insoluble
27
What is produced when a base reacts with an acid?
Salt and water
28
Example of a word equation of a reaction between magnesium oxide and hydrochloric acids
Magnesium oxide + hydrochloric acid —> magnesium chloride + water
29
What is pH neutral?
pH 7
30
What happens as the concentration of hydrogen ions increases?
The pH decreases
31
What is an indicator?
A dye that change colour depending on whether it’s above or below a certain pH
32
What is the reaction between an acid and a base called?
Neutralisation
33
What happens to the products when neutralisation happens?
They become neutral, pH 7
34
What is titration?
A very accurate technique for adding acid to alkali
35
What do strong acids do in water?
Ionise almost completely
36
What does ionising in water mean?
A large portion of the acid molecules dissociate to release H+ ions - tend to have low pH
37
What happens to week acids in solutions?
They do not fully ionise in solution
38
What does it mean if acids don’t fully ionise in solutions?
Only a small proportion of the acid molecules dissociate to release H+ ions - tend to be around 2-6 pH
39
What are alkalis in solution sources of
Hydroxide ions
40
Do acids have high or low pH
Low
41
What does the higher the concentration of hydrogen ions mean in an acidic solution
The lower the pH
42
What does the higher the concentration of hydroxide ions in an alkali solution mean
The higher the pH
43
What happens with an acid-alkali neutralisation
Hydrogen ions (H+) from the acid react with hydroxide ions (OH-) from the alkali to form water
44
What does a dilute acid mean
An acid with a small number of acid molecules compared to the volume of water
45
What is a concentrated acid
An acid with large number of acid molecules compared to the volume of water
46
What colour is litmus when there’s an acid present
Red
47
What colour is litmus in a neutral solution present
Purple
48
What colour is litmus in a alkaline solution present
Blue
49
What colour is methyl orange in a neutral and alkaline solution present
Yellow
50
What colour is methyl orange in an acidic solution present
Red
51
What colour is phenolphthalein in a neutral and acidic solution present
Colourless
52
What colour is phenolphthalein in an alkaline solution
Pink
53
What type of reaction is the ionisation of a weak acid
Reversible
54
What is concentration measured in
g dm(-3) or mol dm(-3)
55
What are salts
Ionic compounds
56
What does an acid + metal make
Salt + water
57
What does acid + metal hydroxide make
Salt + water
58
What does an acid + metal make
Salt + hydrogen
59
What does an acid + metal carbonate make
Salt + water + carbon dioxide
60
What substances are soluble?
Common salts-sodium, potassium, ammonium
Nitrates
Common chlorides (except sliver&lead chloride)
Common sulfates(except lead,barium,calcium sulfate)
61
What substances are insoluble
Silver&lead chloride, lead&barium&calcium sulfate, common carbonates and hydroxides(except sodium&potassium&ammonium ones)
62
How can u make a pure dry sample of an insoluble salt
Precipitation reaction
63
Why is an excess of the reactant used in making soluble salts using an acid and insoluble base
So that u don’t have any leftover acid in your product
64
Why is the excess recant at removed when making a soluble salt from and acid and an insoluble base
To get the solution containing only salt and water
65
Why is titration used if soluble salts are prepared from an acid and a soluble reactant
U need work out exactly the right amount of alkali to neutralise the acid
66
What are electrolytes
Ionic compounds in the molten state or dissolved in water
67
What is electrolysis
A process in which electrical energy, from a direct current supply, decomposes electrolytes
68
Where do positively charged cations go during electrolysis
Migrate to the negatively charged cathode
69
When do negatively charged anions migrate to during electrolysis
The positively charged anode
70
What does OIL RIG stand for
Oxidation is loss
| Reduction is gain
71
WHats an electrochemical cell
A circuit that is made up of the anode, cathode, electrolyte a power source and the wires that connect the 2 electrode
72
How do u write half equations
1) put one of the things being oxidised or reduced on one side of an arrow and thr thing that gets oxidised or reduced to on the other
2) balance up the numbers of atoms
3) all the electrons (e(-)) on to one side to balance charges
73
Half equation of sodium loosing 1 electron to become a sodium ion
Na — Na(+) + e(-)
74
Why can’t ionic solids be electrolysed
Because the ions are in fixed positions and can’t mive
75
What will be produced at the cathode if H(+) and metal ions are present
Hydrogen will be produced
76
What happens if the metal is less reactive than hydrogen at the cathode
Solid layer of thr pure metal will be produced
77
What happens if At the anode is OH(-) and halide ions (Cl(-), Br(-)) are present
then molecules of chlorine, brownie or iodine will be formed
78
What happens at the anode of no halide ions are present
O2 is form3
79
How do you make a soluble salt from an acid and an insoluble base
1) heat the acid in a water bath (speeds up the reaction between the acid and the insoluble base, do in a fume cupboard to avoid releasing acid fumes into room)
2) add the base to the acid-base and acid react to produce a soluble salt and water(when base is in excess-excess solid will sink to bottom of flask)
3) filter off the excess solid to get a solution only containing salt and water
4) heat the solution gently over a Bunsen burner to slowly evaporate some of the water, leave to dry and cool and salt will crystallise, filter off the solid salt and leave to dry
80
How do u do the titration of a soluble salt using an acid/alkali reaction
1) use a pipette to measure out amount of acid into conical flask. Add few drops of iniciaron
2) slowly add alkali to the acid using a bureta until u reach the end point(when acids been exactly neutralised and indicator changes colour)
3) then carry out the reaction using the same volumes of alkali and acid with no indicator - so salt isn’t contaminated with indicator
4) when reaction is complete only salt and water will be left
5) slowly evaporate some of the water and leave solution to crystallise- filter off the solid leave to dry and have pure dry salt
81
Steps of how to make a pure dry sample of an insoluble salt
1) add a spatula of lead nitrate to a test tube, add water to dissolve it(deionised), shake thoroughly to make sure all lead nitrate has dissolved. In separate test tube do same with spatula of sodium chloride
2) tip the 2 solutions into a small beaker and mix, the lead chloride should precipitate out
3) filter the contents of beaker into a conical flask
4) swill out the beaker with more deionised water and tip into filter paper
5) scrape lead chloride onto fresh filter paper and leave to dry in an oven of desiccator
82
What product is formed at the cathode when using the aqueous electrolyte copper chloride
Copper
83
What product is formed at the cathode when using the aqueous electrolyte sodium sulfate
Hydrogen
84
What product is formed at the cathode when using the aqueous electrolyte water acidified with sulfuric acid
Hydrogen
85
What product is formed at the anode when using the aqueous electrolyte copper chloride
Chlorine
86
What product is formed at the anode when using the aqueous electrolyte sodium sulfate
Oxygen
87
What product is formed at the anode when using the aqueous electrolyte water acidified with sulfuric acid
Oxygen
88
What is formed at the cathode in the electrolysis of copper sulfate with inert electrodes
Copper metal
89
What is formed at the anode from the electrolysis of copper sulfate using inert electrodes
Oxygen and water
90
What happens at the anode from electrolysis of copper sulfate using copper (non inert) electrodes
The mass of the anode decreases
91
What happens at the cathode from electrolysis of copper sulfate using copper (non inert) electrodes
Mass of the cathode increases
92
What do u need to purify copper by electrolysis
An electrochemical cell, copper electrodes
93
What happens during the process of purifying copper
1) the impure copper anode is oxidised , dissolving into the electrolyte to form copper ions
2) the copper ions are reduce at the pure copper cathode and add to its layer of pure copper
3) any impurities from the impure copper anode sink to the bottom of the cell forming a sludge
