Section 1 - Pgs 3-9, 16-28 Flashcards
1
Q
What is an atom?
A
A particle, without charge, that is made up of protons, neutrons and electrons.
2
Q
What is a molecule?
A
Two or more atoms joined together by covalent bonds.
3
Q
What is the structure of atoms?
A
- Central nucleus containing protons and neutrons
- Surrounded by shells of electrons
4
Q
What is the charge of the nucleus?
A
Positive
5
Q
What does the nucleus contain?
A
Protons and neutrons
6
Q
Relative to the whole atom, how big is the nucleus?
A
Tiny
7
Q
What do electrons move around the nucleus in?
A
Energy levels called shells
8
Q
What is the mass of each sub-atomic particle?
A
Proton = 1 Neutron = 1 Electron = 0.0005
9
Q
What is the charge of each sub-atomic particle?
A
Proton = +1 Neutron = 0 Electron = -1
10
Q
In a neutral atom, the number of electrons…
A
… Equals the number of protons.
11
Q
What happens if electrons are added to or removed from an atom?
A
It becomes charged and is now an ion.
12
Q
What is an ion?
A
A charged atom.
13
Q
What is the mass number?
A
The total number of protons and neutrons.
14
Q
What is the atomic number?
A
The number of protons.
15
Q
What defines which element an atom is of?
A
The number of protons (atomic number).
16
Q
Which number (mass or atomic) is larger?
A
Mass number
17
Q
How do you work out the number of neutrons in an atom?
A
Mass number - Atomic number = No. of Neutrons
18
Q
What are isotopes?
A
Different atomic forms of the same element, which have the same number of protons but different numbers of neutrons.
19
Q
What sub-atomic particles define the chemical properties of an atom?
A
The number of electrons.
20
Q
Are isotopes chemically identical and why?
A
Yes, because they have the same number of electrons, which is what defines the chemical properties.
21
Q
What is relative atomic mass?
A
The weighted average mass of the isotopes of that element. It is measured on a scale where carbon is exactly 12.
22
Q
How many electrons can occupy each of the first 3 shells?
A
1st shell: 2
2nd shell: 8
3rd shell: 8
23
Q
What is the significance of an atom having an outer shell which is not full?
A
It makes the atom want to react so that it has a full outer shell.
24
Q
What do atoms want in terms of outer shells?
A
They want a full outer shell.
25
What is relative abundance of an isotope?
- How much of a certain isotope there is compared to the total amount of the element in the world.
- It can be a ratio, fraction or percentage.
26
How is relative atomic mass symbolised?
Ar
27
How do you calculate Ar (relative atomic mass)?
1) Multiply the mass of each isotope by its relative abundance.
2) Add those together.
3) Divide by the sum of relative abundances.
28
Which shell can actually hold more than 8 electrons?
3rd
29
How many different atoms are there?
About 100 or so.
30
What is a diatomic molecule?
A molecule with two atoms in it.
31
What is an element?
A material made up of only one type of atom.
32
What is it called when atoms go round in pairs?
Diatomic molecules
33
What is a compound?
A compound made of two or more different elements which are chemically bonded together.
34
Are the properties of a compound similar to those of the original elements it is made from?
No, they are often very different.
35
What is a mixture?
A combination of elements, which are not chemically bonded together.
36
How can the chemical properties of a mixture be described?
A mixture of the separate parts.
37
Compare how easily compounds and mixtures can be separated out.
Compounds are difficult to separate out, while mixtures are easy to separate out.
38
Is crude oil a compound or mixture?
A mixture of different length hydrocarbons.
39
What is filtration used for?
Separating an insoluble solid from a liquid (often in purification)
40
Describe filtration.
A liquid with a solid innit is passed through filter paper in a funnel.
41
What is distillation used for?
The separating of mixtures that contain liquids.
42
What are the types of distillation?
Simple and fractional
43
What is simple distillation used for?
Separating a liquid from a solution.
44
Describe simple distillation.
1. Solution is heated
2. Part of solution with lowest boiling point evaporates
3. Vapour is cooled, condensed and collected
4. Rest of solution stays in flask
(This only works with things with very different boiling points)
45
What is the problem with simple distillation?
It can only be used to separated out things with very different boiling points.
46
What process is used to separate water from seawater?
Simple distillation
47
What is fractional distillation used for?
Separating out a mixture of liquids with similar boiling points.
48
Describe fractional distillation.
1. Put mixture in a flask and put a fractionating column on top
2. Heat the mixture
3. Different liquids evaporate different temperatures -> This allows them to be collected separately
4. Once all of one liquid is collected, raise the temperature until the next liquid can be collected
49
What is the difference between when you might use simple distillation and fractional distillation?
Simple distillation is used to separate things with completely different boiling points (e.g. salt and water), while fractional distillation is used to separate liquids with similar boiling points (e.g. crude oil).
50
How many elements are there?
About 100
51
What is the periodic table sorted by?
Increasing atomic number
52
What are vertical columns in the periodic table called?
Groups
53
What does an element's group tell us?
The number of electrons it has in its outer shell.
54
What are group 1 elements called?
Alkali metals
55
What are group 7 elements called?
Halogens
56
What are group 0 elements called?
Noble gases
57
What determines an element's properties?
The number of electrons (in the outer shell).
58
What is crystallisation used for?
Separating a soluble solid from a solution.
59
Describe crystallisation.
1. Pour the solution in an evaporating dish
2. Slowly heat the solution until crystals start to form
3. Let the solution evaporate -> Creates big crystals
4. Dry the crystals using a drying oven or desiccator
60
What is rock salt made of?
Mixture of salt and sand
61
How can rock salt be separated?
1. Grind the rock salt with a pestle and mortar.
2. Dissolve in a beaker.
3. Filter through filter paper.
4. Evaporate the solution in an evaporating dish.
62
What is chromatography?
The separating of mixtures (usually dyes)
63
Describe the process of chromatography.
1. Draw a line near the bottom of some filter paper.
2. Add spots of different dyes along the line at regular intervals
3. Put the sheet in a beaker of solvent
4. The solvent depends on what's being tested
5. Make sure the dyes aren't touching the solvent
6. Place a lid on the beaker -> Stops evaporation
7. Solvent seeps up the paper, carrying the dyes with it
8. Each dye will form a spot
64
What is the pattern of spots at the end of chromatography called?
A chromatogram
65
Why does chromatography work?
Different dyes move up the paper at different rates due to their solubility in a solvent.
66
What factors affect the distance a specific dye will move up the paper in chromatography?
1. Solvent used
| 2. Paper used
67
How can chromatography be used to find which dyes are in a mixture?
Chromatograms are made for some reference dyes. When the test mixture is separated, the heights to which each dye travels can be compared to the reference. If a dye reaches an equal height to the reference dyes, they are the same.
68
What is the state symbol use in equations for a solid?
(s)
69
What is the state symbol used in equations for a liquid?
(l)
70
What is the state symbol used in equations for a gas?
(g)
71
What is the state symbol used in equations for an aqueous solution?
(aq)
72
What is relative formula mass?
The relative atomic masses of all the atoms in a compound added together.
73
What is the symbol for relative atomic mass?
Mr
74
What is Mr?
The relative atomic mass.
75
What is the empirical formula?
The simplest ratio of atoms in a compound.
76
How can the empirical formula be calculated?
1. List the masses or percentages of each element
2. Divide each one by its Ar to find the number of moles
3. Use these to find the simplest ratio between the elements
77
Is the empirical formula the same as the molecular formula?
No, empirical formula is the simplest ratio, while molecular formula is the actual number of each atom in a compound.
78
How can the mass of a product in a reaction be calculated when only the mass of one of the reactants is given?
1. Calculate the moles of the reactant (Mass/Mr)
2. Use the ratio of the reactant to the product to find the number of moles of the product
3. Calculate the mass of the product (Moles x Mr)
79
What is the yield of a reaction?
The mass of the product produced by a reaction.
80
What is the formulas for percentage yield?
% Yield = (Actual yield / Theoretical yield) * 100
81
What is a mole?
The number of atoms or molecules of an element or compound which weigh as much as the Ar or Mr. (e.g. 1 mole of carbon weighs 12g)
It is always 6.023 x 10^23
82
What is the number of atoms in a mole?
6.023 x 10^23
83
What is Avogadro's constant?
* It is the number of particles in 1 mole of a substance.
| * It is always 6.023 x 10^23
84
What is molar mass?
The mass of 1 mole of a substance (e.g. The molar mass of carbon is 12g)
85
What is the formula for moles?
Moles = Mass / Mr
86
What is the structure of all solid salts?
Lattice of positive and negative ions.
87
What does it mean when a salt is hydrated?
There are water molecules incorporated in the lattice of positive and negative ions.
(i.e. When it contains water of crystallisation)
88
What is the water in a salt lattice called?
Water of crystallisation
89
What causes the water molecules in a hydrated salt to be held in place?
The positive charges on the H+ and negative charge on the O2- causes the water to be attracted to ions in the salt.
90
What is a salt said to be when it contains no water?
Anhydrous
91
How can you tell how much water a hydrated salt contains?
Its formula tells you the ratio of the salt to the water (e.g. CuSO4.5H2O)
92
How can most hydrated salts be made anhydrous?
Heating them
93
How can the masses of a salt when it is hydrated and anhydrous be used to calculated the formula (the formula is usually given like MgSO4.XH2O)?
1. Calculate the moles of water lost (Mass / Mr)
2. Calculate the moles of anhydrous salt made (Mass / Mr)
3. Work out the ratio of moles of anhydrous salt to moles of water
4. This allows the X in the formula to be complete
5. X has to be a whole number so rounding may be required
94
What is Avogadro's Law?
One mole of any gas occupies 24 dm3 (at RTP)
95
Wat volume does 1 mole of gas occupy?
24 dm3
96
What is the molar volume?
The volume that a mole of gas takes up.
97
What is the molar volume at RTP?
24 dm3
98
How many cm3 are in a dm3?
1000cm3
99
What is 24,000cm3 in dm3?
24dm3
100
What is the formula for volume of a gas (relative to moles)?
Volume (dm3) = Moles x 24
OR Volume (dm3) = (Mass / Mr) x 24
101
What is RTP?
Room temperature and pressure (25*C and 1 atm)
102
How can the volume of gas produced in a reaction be calculated?
1. Calculate the number of moles as usual
| 2. Multiply by 24 (for dm3) or 24000 (for cm3) to get the volume.
103
What is concentration?
The number of moles or grams per unit volume of a substance.
104
What are the units for concentration?
• Moles per dm3 (mol/dm3)
OR
• Grams per dm3 (g/dm3)
105
What is the formula for concentration?
Concentration (mol/dm3) = Moles / Volume
106
How do you convert from mol/dm3 to g/dm3?
1. Convert from moles to grams using the formula "Moles = Mass / Mr"
2. Put this number over dm3
107
Give some examples of charge carriers.
Electrons and ions
108
What are charge carriers?
Ions and electrons which can move charge around a system to create a flow of electricity.
109
What is electric current?
The flow of electrons or ions.
110
Can ionic compounds conduct electricity?
Only when molten or in solution.
111
Why can't ionic compounds conduct electricity when solid?
The ions aren't free to move around.
112
Why can ionic compounds conduct electricity when molten or dissolved?
The ions are free to move around.
113
Do covalent compounds conduct electricity?
No, they have no ions or free electrons.
114
Describe the bonding in metals.
* Giant structure of positive ions surrounded by a sea of delocalised electrons
* Attraction between positive ions and negative electrons is called metallic bonding
115
What is metallic bonding?
The attraction between the giant structure of positive ions and a sea of delocalised electrons in a metal.
116
What are the properties of metals and why?
* Good conductors of electricity and heat -> Due to their free electrons.
* Malleable -> Layers of atoms can slide over each other
117
What is electrolysis?
Passing an electric current through an ionic substance to break it down into new substances.
118
What state must the electrolyte be in during electrolysis?
Molten or in solution
119
What is the substance being electrolysed called?
Electrolyte
120
Why must the electrolyte be molten or in solution during electrolysis?
This gives it free ions which can conduct electricity.
121
What happens in terms of electrons at each electrode during electrolysis?
* Anode (+) - Electrons taken away from ions
| * Cathode (-) - Electrons given to ions
122
What happens when ions when they gain or lose electrons during electrolysis?
They become atoms or molecules.
123
What are the two ways of determining whether a liquid is an electrolyte?
1. Conductivity probe -> Gives you a reading if the liquid is a conductor
2. Electrolysis -> Doing electrolysis as usual tells you if the substance is an electrolyte
124
What is the difference between the electrolysis of molten ionic compounds and the electrolysis of aqueous solutions?
* Molten ionic compounds -> The products at each electrode will always be the two ions in the compound
* Aqueous solutions -> The products are each electrode can be either the ions or hydrogen or oxygen (depending on reactivity)
125
What is the cathode?
The negative electrode.
126
What is the anode?
The positive electrode.
127
What are cations?
The positive ions attracted to the cathode.
128
What are anions?
The negative ions attracted to the anode.
129
During electrolysis, how does the direction of current affect which electrode is which?
The first electrode the current reaches from the battery is the cathode (-).
130
What type of ions are anions?
Non-metals (and OH- in aqueous solution)
131
What type of ions are cations?
Metals (and H+ in aqueous solutions)
132
Describe what happens at the anode during electrolysis of molten ionic compounds.
The negative non-metal ions lose electrons to the cathode to become atoms.
133
Describe what happens at the cathode during electrolysis of molten ionic compounds.
The positive metal ions gain electrons from the cathode to become atoms.
134
What are the electrodes made from during electrolysis?
Inert (unreactive materials) such as carbon
135
Using ionic equations describe the electrolysis of lead bromide.
ANODE
2Br- -> Br2 + 2e-
CATHODE
Pb2+ + 2e- -> Pb
136
Why is the electrolysis of aqueous solutions different to the electrolysis of molten ionic compounds?
Aqueous solutions also contain H+ and OH- ions from the water.
137
What things could be produced at the anode during the electrolysis of aqueous solutions?
Oxygen or Halogens
138
What things could be produced at the cathode during the electrolysis of aqueous solutions?
Hydrogen or Metals
139
What decides what is produced at the anode during electrolysis of aqueous solutions?
* If halide ions (Cl-, Br-, I-) are present -> Chlorine, bromine or iodine are produced
* If no halide ions are present -> Oxygen is produced
140
What decides what is produced at the cathode during electrolysis of aqueous solutions?
* If the metal is more reactive than hydrogen -> Hydrogen produced
* If the metal is less reactive than hydrogen -> Metal produced
141
What is the ionic equation for hydrogen forming at the cathode?
2H+ + 2e- -> H2
142
What is the ionic equation for oxygen forming at the anode?
4OH- -> O2 + 2H2O + 4e-
143
What is formed during the electrolysis of sulphuric acid?
* Anode: Oxygen and water
| * Cathode: Hydrogen
144
What ions are found in sulphuric acid?
SO4-, H+, OH-
145
What ions are found in sodium chloride solution?
Na+, Cl-, H+, OH-
146
What is formed during the electrolysis of sodium chloride solution?
* Anode: Chlorine
| * Cathode: Hydrogen
147
What ions are found in copper sulphate solution?
Cu2+, SO4 2-, H+, OH-
148
What is formed during the electrolysis of copper sulphate solution?
* Anode: Oxygen and water
| * Cathode: Copper
149
What affects the amount of product made by electrolysis?
The number of electrons that are transferred.
150
How can you increases the amount of a substance produced by electrolysis?
* Electrolysing for a longer time
| * Increasing the current
151
What are the units for charge in electrolysis?
Coulombs (and Faradays)
152
What is a coulomb?
The unit for charge
153
What is the equation for charge?
Charge (C) = Current (A) x Time (s)
Q = I x t
154
What is a faraday?
96,000 coulombs -> This is exactly 1 mole of electrons
155
How many moles of electrons (faradays) are needed to turn one mole of sodium ions into sodium atoms?
1 mole (because the sodium only has a charge of 1+)
156
How many moles of electrons (faradays) are needed to turn one mole of zinc ions into zinc atoms?
2 moles (because the zinc has a charge of 2+)
157
How many moles of electrons (faradays) are needed to turn one mole of aluminium ions into aluminium atoms?
3 moles (because the aluminium has a charge of 3+)
158
Describe how the amount of a product of electrolysis can be calculated using only the current and time it has been flowing for.
1. Write out the balanced HALF-equation for the product
2. Calculate the charge (Q = I x t)
3. Calculate the faradays / moles of electrons (divide the charge by 96,000)
4. Calculate the moles of the product (look at the ratio of moles of electrons and the product in the equation)
5. Calculate the mass of the product (Moles = Mass / Mr)
