Chemistry (Paper 1) Flashcards
(242 cards)
1
Q
Who developed the periodic table?
A
Dmitri Mendeleev
2
Q
Who created the Billiard Ball Model?
A
Dalton
3
Q
What model did JJ Thompson propose?
A
The plum pudding model
4
Q
Who created the Bohr model?
A
Rutherford
5
Q
What type of elements are involved in ionic bonding?
A
A metal and non metal
6
Q
Relative mass of an electron
A
0
7
Q
What is an ion?
A
A charged atom
8
Q
What type of bonding involves only non metals?
A
Covalent bonding
9
Q
Ionic bond definition
A
Electrostatic attraction between oppositely charged ions (when electrons are transferred from metal atoms to non metal atoms)
10
Q
Electrostatic force
A
A force of attraction between particles with opposite charges
11
Q
What is filtration?
A
Method that separates an insoluble solid from a liquid
12
Q
Ionic compounds exist as
A
Giant ionic lattices
13
Q
Electricity definition
A
A flow of charge
14
Q
Why do ionic lattices have high melting and boiling points?
A
Large amounts of energy is required to break the strong ionic bonds
15
Q
Why do ionic lattices only conduct electricity when liquid or dissolved in water
A
The ions are free to move and so charge can flow through the structure.
16
Q
The number of electrons an atom needs to get a full outer shell in covalent bonding is equal to
A
the number of bonds that an atom can form
17
Q
Intermolecular force
A
A force between molecules
18
Q
Weak intermolecular forces are overcome when..
A
simple molecular structures melt or boil
19
Q
Simple molecular structures have no
A
overall charge
20
Q
Covalent bond definition
A
Shared pair of electrons (between non metals)
21
Q
Simple molecular structures are usually liquids or gases because
A
the intermolecular forces are so weak, not much energy is required
22
Q
small molecules have a low boiling point whilst large molecules have a higher boiling point because..
A
as the size of the simple molecule increases so does the strength of the intermolecular forces therefore more energy is required to break/overcome the forces
23
Q
What element is diamond, graphite and fullerene made of?
A
Carbon
24
Q
Polymers are
A
Long chain of molecules held together by strong covalent bonds
25
Why are polymers solid at room temperature?
The intermolecular forces are relatively strong.
26
Polyatomic ions definition
• Ions made from more than one charged atom (and are covalently bonded together)
• Eg Nitrate (NO3 -)
27
Formula for Nitrate
NO3-
28
Sulfate formula
SO4 2-
29
Hydroxide formula
OH-
30
Carbonate formula
CO3 2-
31
Ammonium formula
NH4 +
32
Pure metals are (soft/hard)
Soft
33
Alloys are (soft/hard)
Hard
34
Why are pure metals soft?
The atoms are the same size therefore they are in an orderly arrangement and layers are able to slide over each other (malleable)
35
Why are alloys hard?
The atoms are different sizes therefore there is a disorderly arrangement and the layers are distorted. Therefore layers can’t slide over each other
36
Molecule definition
Atoms chemically bonded together
37
Why is a diamond very hard?
• It is a giant covalent lattice with 4 strong covalent bonds between each atom
• A large amount of energy is required to break the bonds apart
38
Allotrope definition
A different structural form of an element eg Diamond and Graphite
39
What does PANIC stand for?
Positive Anode, Negative Is Cathode
40
Graphene
• A single layer of graphite
• Used for drug delivery or in electronics
41
Properties of transition metals (1)
• Less reactive than group 1 metals
• shiny and malleable
• sonorous
• electricity and heat conductor
42
Properties of transition metals (2)
• catalysts for chemical reactions
• form coloured compounds
• high melting and boiling points
• able to have different charges
43
Electroplating definition
Using electrolysis to coat an object in a thin layer of a metal
44
What is electroplating used for?
To protect objects from corroding or to improve its appearance
45
What is the structure of a metal?
A lattice of positive metal ions attracted to delocalised electrons
46
Alloy definition
Mixture of a metal with small amounts of other elements
47
What elements are found in steel?
Iron (main element) and carbon
48
What elements are found in brass?
Copper (main element) and zinc
49
What elements are found in bronze?
Copper (main element) and tin
50
What elements are found in an aluminium alloy (aka magnalium)
Aluminium (main element) and magnesium
51
Corrosion definition
Destruction of a material by reaction with oxygen
52
Rusting definition
Corrosion of iron or steel
53
Electrolyte definition
an ionic compound that is dissolved in water and conducts electricity during electrolysis
54
Positive electrode
Anode
55
Negative electrode
Cathode
56
Why do solid ionic compounds not conduct electricity?
Their ions aren’t free to move therefore charge is unable to flow through the structure
57
What is zinc beneficial for?
killing bacteria
58
How does sacrificial protection work?
When a more reactive metal is used to coat a metal so that it corrodes instead
59
Empirical formulae meaning
The simplest whole number ratio of atoms or ions in a substance
60
How are chemical reactions sped up?
By heating them
61
How to find empirical formula?
• Mass or percentage of the atom/ion over the atomic masses
• Divide results by the smallest answer
• Use the ratio as the subscripts
62
Concentration equation
Mass/Volume
63
Negative ion
Anion
64
Methods for corrosion prevention
Electroplating and sacrificial protection
65
unit for concentration
g dm-3
66
Law of conservation of mass
The mass of reactants and products are the same in a reaction
67
Mole meaning
Unit for measuring the number of particles
68
Relationship between a mole and Avogadro’s constant
1 mole of a substance contains 6.02 x10^23 particles of that substance
69
RFM meaning
Relative formula mass (sum of atomic masses of the elements in the molecule)
70
How can the concentration of a solution be increased?
•Increasing the mass of the solute • decreasing volume of solvent
71
Concentration definition
How much solute is dissolved in a volume of solvent
72
Equation to work out the Mass of a substance
Mr x moles
73
1 dm3 =
1L or 1000cm3
74
Experiment to find the mass of oxygen reacting with magnesium
• strongly heat magnesium ribbon in crucible • lift lid occasionally to let in oxygen • measure mass of magnesium oxide at end • subtract the mass of magnesium at start
75
1 ton = how many grams
1,000,000 grams
76
1 mg = how many grams
1/1000 grams
77
1 mole of a substance weighs the same as
the Ar or Mr of the substance (in grams)
78
What are the 4 separation techniques?
filtration, crystallisation, distillation and chromatography
79
Crystallisation
• To make crystals out of a solution by evaporating it
• Separates a soluble salt from a solution
80
How to calculate percentage yield
Actual yield / theoretical yield x 100
81
Toxic meaning
Something that causes death
82
Why are reagents used in excess?
To ensure all of the other reactant reacts
83
What does reagent mean?
Reactant
84
Limiting reagent meaning
A reagent not in excess that limits how much product is made
85
Yield definition
The mass of product produced by a chemical reaction
86
Stoichiometry meaning
Ratio of moles that react
87
Why do some reactions produces a small yield?
• Unwanted side reactions
• Incomplete reactions
• Product left behind on apparatus
88
What are the diatomic elements?
hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), and iodine (I)
89
What is concentration measured in (using moles)?
Mol/dm³
90
Equation to work out moles (from the concentration of a solution)
Concentration x volume
91
Unit for measuring volume
dm³
92
What’s a titration?
An accurate method to measure the concentration of acids and alkalis
93
How are titrations carried out?
• Add alkali to conical flask using pipette
• Add universal indicator to flask
• Fill burette with acid and add it to conical flask, swirling as you go
• Go drip wise near endpoint/ colour changes to green
• Repeat
94
How to calculate atom economy %
(Mr of desired product \ Mr of all products) x 100
95
How to calculate volume (Avogadro’s law)
24 x moles
96
What is Avogadro’s Law?
1 mole of any gas (at room temperature and pressure) has a volume of 24 dm³
97
[Topic 3]
State symbol for aqueous
aq
98
What makes a solution acidic?
Positive hydrogen ions (H+)
99
Bases meaning
Substances which can neutralise an acid, forming a salt and water
100
Alkali meaning
A base that can dissolve in water to produce hydroxide ions in a solution
101
What are the most common bases?
• Metal oxides eg CaO
• Metal hydroxides eg Ca(OH)2
• Metal carbonates CaCO3
102
What substance do alkalines produce in water?
Negative hydroxide ions (OH-)
103
Wasp stings are
Basic
104
Bee stings are
Acidic
105
What are indicators?
Substances that change colour when added to an acid or alkali
106
How does a litmus indicator function?
**In an acidic solution:** It turns red
**In an alkaline solution:** It turns blue
**In a neutral solution:** It turns purple
107
How does the phenolphthalein indicator function?
**In an acidic solution:** It’s colourless
**In an alkaline solution:** It turns pink
108
How does a methyl orange indicator function?
**In an acidic solution:** It turns red
**In an alkaline solution:** It turns yellow
109
How can pH be measured?
• Universal Indicator solution • Digital pH meter
110
Apparatus used in a titration
• Bunsen burner • Burette • Glass pipette • Indicator • Conical flask • Acid and alkali
111
What are common acids?
• Sulfuric acid (H₂SO₄)
• Hydrochloric acid (HCL)
• Nitric acid (HNO₃)
112
Symbol equation for dissolved hydrochloric acid
HCL (aq) —> H+(aq) + Cl-(aq)
113
Symbol equation for dissolved sodium hydroxide (Alkali)
NaOH (aq) —> Na+(aq) + OH-(aq)
114
What does green indicate on a universal indicator?
The substance is neutral
115
What happens when an acid reacts with an alkali
Neutralisation occurs • The H+ ions react with OH- ions to produce water
116
Word equation and ionic equation for the reaction between an acid and alkali
Acid + alkali —> salt + water
H+ + OH- —> H2O
117
What occurs in the process at which the pH of an acidic solution changes as it reacts with a base?
• The pH increases slowly at first because there’s excess H+ ions
• Increases rapidly as more OH- ions from the alkali is added
• Then increases at a slower rate because there’s excess OH- ions
118
Chemical formulae for acids
Sulfuric acid - H₂SO₄
Nitric acid - HNO₃
Hydrochloric acid - HCl
Ethanoic acid - CH₃COOH
119
Common salts
Sulfates
Chlorides
Nitrates
Phosphates
Ethanoates
Citrates
120
Common alkalis and their formulae
Ammonia NH3
Calcium hydroxide Ca(OH)₂
121
Dilute acids have
Few H+ ions in the solution
122
Concentrated acids have
Lots of H+ ions in the solution
123
What happens when acids dissolve in water?
They ionise (separate into ions) to release hydrogen ions in the solution
124
What makes an acid strong?
• When the molecules ionise fully
• To release H+ ions
125
What makes an acid weak?
When the molecules only ionise partially
126
In a weak acid, the reaction is ________
Reversible
127
Ionic equation for weak acids
HX ⇌ H+ + X-
128
How is pH value calculated?
Using the concentration of hydrogen ions in a solution
129
What would decreasing the pH of a solution by 1 do?
It would increase the concentration of H+ ions by a factor of 10
130
Metal + acid —>
Salt + hydrogen
131
Metal oxide + acid —>
Salt + water
132
Metal hydroxide + acid —>
Salt + water
133
Metal carbonate + acid —>
Salt + water + carbon dioxide
134
Ammonia + acid—>
Ammonium salt
135
Test for hydrogen
When a lit splint goes out with a squeaky pop
136
Test for carbon dioxide
When you bubble the gas through limewater and it turns cloudy white
137
Method to make pure dry crystals of a salt
(Making a soluble salt from an insoluble base)
• Add the **[named insoluble base]** to the **[named warm acid]** until the base is in excess
• Filter the solution to remove the excess base
• Pour the filtrate into an evaporating basin and gently heat it to evaporate some water
• Stop heating when half the solution remains
• Leave the solution to evaporate
• Filter, wash and dry the crystals
138
When a solution ends in -ate what does it contain?
Oxygen
139
How to make a soluble salt using a soluble reactant
Acid-alkali titration:
• Do a trial run to show roughly what volume is needed for neutralisation
• Perform several attempts and calculate a mean volume using reproducible results
• After establishing the required volume repeat the neutralisation reaction without indicator
• Obtain the solid salt by evaporation/crystallisation
140
Methods to produce a salt
• Making a soluble salt from an insoluble base (evaporation)
• Making a soluble salt using a soluble reactant (titration)
• Making an insoluble salt using soluble salts (filtration)
141
How to prepare an insoluble salt
• Two soluble salt solutions are mixed together in a beaker and a white precipitate of the insoluble salt is formed
• The precipitate is filtered off
• The filtered precipitate is washed several times with deionised (pure) water which prevents a reaction with the salt from occurring
• The insoluble salt is carefully scraped off the filter paper into a dish and dried in an oven
142
Substances soluble in water
• Sodium, potassium and ammonium compounds (carbonates and hydroxides)
• All nitrates
• Most chlorides
• Most sulfates
• Calcium hydroxide
143
Substances insoluble in water
• Silver chloride
• Lead chloride
• Lead sulfate
• Barium sulfate
• Calcium sulfate
• Most carbonates
• Most hydroxides
144
Zinc ion formula
Zn (2+)
145
Oxide ion formula
O (2-)
146
Nitride ion
N (3-)
147
Electrolysis meaning
The breakdown of an ionic compound using electricity
148
The electrolyte must be..
Molten or in an aqueous solution
149
Positive ion
Cation
150
Negative ion
Anion
151
Why can electrolytes only conduct electricity when molten or in solution
The ions are free to move therefore charge can flow
152
How is indicator paper used to determine the pH of a mixture?
• Look at the colour of the indicator
• Compare it to the chart
153
When the air hole of a Bunsen burner is open, the flame is
a roaring blue flame
154
Methane (CH4) exists as a
simple molecule
155
Graphite has a (high/low) melting point because
• High
• It’s a giant covalent lattice where the atoms are strongly bonded together
• A large amount of energy is required to break them apart
156
OILRIG acronym
• Oxidation is Loss
• Reduction is Gain
157
What word is used to remember the process that occurs at the anode?
Anox
(Anode oxidation)
158
What word is used to remember the process that occurs at the cathode?
Redcat
(Reduction cathode)
159
Half equation for chlorine
2Cl - -> Cl2 + 2e -
160
Half equation for zinc ion
Zn2+ + 2e - -> Zn
161
Rules for electrolysis of an aqueous electrolyte
• The least reactive cation is reduced at the cathode
• If a halide is present the halogen is produced at the anode
• If there isn’t, oxygen is produced at the anode
162
Half equation for oxygen produced in the electrolysis of an aqueous solution
4OH - —> 2H2O + O2 + 4e-
163
What process happens at the anode?
Oxidation (losing electrons)
164
What process happens at the cathode?
Reduction (gaining electrons)
165
Observation at anode during electrolysis of copper sulfate solution
The electrolyte bubbles (oxygen is present)
166
Observation at cathode during electrolysis of copper sulfate solution
Red-brown solid (copper)
167
Why must the electrodes be inert?
So that the electrodes themselves do not react with the ions in the solution
168
Inert meaning
Unreactive
169
Using copper electrodes in electrolysis
• At the impure copper anode, copper atoms lose electrons (oxidation)
• Copper ions enter the solution
• The Cu 2+ ions get attracted to the cathode
• At the cathode the ions gain electrons and become atoms coating the electrode
• As the anode breaks down any impurities remain in the electrolyte
170
Why does the mass of the anode change during electrolysis using copper electrodes?
• It gets lighter because it loses copper
• The copper atoms are oxidised and lose 2 electrons to become copper ions that dissolve into the electrolyte
171
Why does the mass of the cathode change during electrolysis using copper electrodes?
• It gets heavier because it gains copper
• Copper ions are reduced and gain 2 electrons to become copper atoms
172
What steps are required before weighing the copper electrodes?
• Clean with emery paper
• Dip into acetone
173
Test for oxygen
A glowing splint relights when placed in a test tube
174
Fullerene
• Graphene rolled into a tube/sphere
• Simple molecule
• Conducts electricity
• Used as a lubricant or in drug delivery
175
Where are metals found?
In rocks in the Earth’s crust
176
What is an ore ?
A rock containing metal
177
What are metals called when they are found in their natural form?
- Uncombined or native
- They are unreactive metals
178
What is distillation?
A process used to separate liquids based on their boiling points
179
What are the two types of distillation?
• Simple distillation
• Fractional distillation
• Simple distillation can’t separate liquids with similar boiling points whereas fractional distillation can
180
What is chromatography?
A method used to separate a mixture of soluble substances
181
Two phases of chromatography
• Stationary phase (where the molecules **can’t** move)
• Mobile phase (where the molecules **can** move)
182
Difference between the 2 types of distillation
Fractional distillation can separate liquids with similar boiling points whereas simple distillation can’t
183
The reactivity of a metal is related to
its tendency to form positive ions and react with oxygen
184
Why do we react metals with acid sometimes?
They are not reactive enough to react with water
185
What substances are used to determine the reactivity of a metal?
• Water
• Acid
186
Metal + Oxygen —>
Metal Oxide
187
Metal + Acid —>
Salt + Hydrogen
188
Metal + Water —>
Metal Hydroxide + Hydrogen
189
What are the products of this reaction and what is it an example of?
Sodium + Iron oxide —>
• Sodium oxide + Iron
Example of a:
• Displacement reaction
• Redox reaction
190
Tendency meaning in terms of reactivity
How readily a metal forms ions
191
Which metals do not react with water or acid?
• Copper
• Silver
• Gold
192
What is a redox reaction?
A reaction where one substance is reduced and another is oxidised
193
Metal extraction methods
• Heating with carbon
• Electrolysis
194
How is the reactivity series used to determine whether a metal can be heated by carbon?
• If a metal is less reactive than carbon it can be extracted using reduction with carbon
• Anything more reactive than carbon requires electrolysis
195
General equation for reduction with carbon
Metal oxide + Carbon —> Metal + Carbon dioxide
196
Why is heating by carbon a better option compared to electrolysis?
It’s cheaper as it uses less energy
197
Types of bonds and structures
• Ionic —> Ionic lattice
• Covalent —> Giant covalent/Polymers/Simple molecules
• Metallic —> Metals (metallic lattice)
198
Graphite characteristics
• Each carbon atom has one delocalised electron
• Giant covalent structure
• Conducts electricity
• Soft as only weak IMFs exist between layers
• Acts as lubricant
199
Why can graphite can act as a lubricant?
Layers can slide over each other due to the weak forces between them
200
Diamond characteristics
• Giant covalent lattice
• Doesn’t conduct electricity as it has no free electrons
• Very hard
• Used in drill bits or jewellery
201
How did Mendeleev order the periodic table?
• He ordered it by atomic mass
• He grouped elements with other ones with similar properties
• He left gaps for elements that haven’t been discovered yet
202
Why did Mendeleev swap some elements round?
• Ordering by atomic mass didn’t fit the pattern
• Some of the atomic masses he used were wrong due to the presence of isotopes
203
Difference between the melting point of a pure substance and impure substance
Pure substances have 1 melting point whereas impure substances have a range of melting points
204
What is a life cycle assessment?
An assessment that calculates the environmental impact of the stages in a product’s life
205
Key processes in a product’s life cycle
• Extracting and processing raw materials
• Manufacturing and packaging
• Using and reusing
• Disposing
• (including transport and distribution at each stage)
206
Benefits of recycling
• Natural reserves of metal ores will last longer
• Minimises noise and dust pollution caused by mining
• Less energy is required than mining
• No habitat destruction
• Provides job opportunities
207
Disadvantages of recycling
• It can be more expensive & more energy demanding to recycle than to extract new metal
• Costs and energy are involved with collecting, sorting and transporting metals
208
High grade ore definition
Rock that contains a high percentage of metal
209
Low grade ore definition
Rock that contains a low percentage of metal
210
Why do we need alternative metal extraction methods?
High grade ores have run out so we need alternative methods of extracting metals from low grade ores
211
Alternative metal extraction methods
• Phytomining
• Bioleaching
212
How is phytomining carried out?
• Plants are used to absorb metal compounds from low grade ore soil
• These accumulate in the plant’s shoots
• Plants are harvested then burned
• Metal compounds are concentrated in solution
• Metal compounds are extracted from the ash
213
What does bioleaching involve?
Bacteria feeding on low grade ores to produce a solution of copper ions (leachate)
214
Advantages of bioleaching
• Doesn’t require high temperatures
• No harmful gases like sulfur dioxide is produced
• Causes less damage to landscape than mining
• Conserves supplies of higher grade ores
215
Disadvantage of bioleaching
It’s very slow
216
Advantages of phytomining
• It can extract metals from contaminated soils
• No harmful gases like sulfur dioxide is produced
• Causes less damage to landscape than mining
• Conserves supplies of higher grade ores
217
Disadvantage of phytomining
Its slow
218
How is ammonia produced?
• Using the Haber process where:
• Temperature = 450°C
• Pressure = 200 atm (atmospheres)
• Catalyst = Iron
219
What is ammonia mainly used for?
Making fertiliser
220
What is the balanced symbol equation for ammonia production
N2 + (3)H2 ⇌ (2)NH3
221
How is nitrogen obtained?
In the air
222
How is hydrogen obtained?
Natural gas
223
Dynamic equilibrium meaning
The forward and backward reactions are both happening at the same rate (reversible reactions)
224
What does a simple cell consist of?
• 2 electrodes made of metals with different reactivities
• An electrolyte (salt solution/ acid)
(typically KOH)
225
What is a fuel cell?
• A cell that produces electrical energy using a reaction between a fuel (often H2) and oxygen
• Water is the only product
226
What are the negative and positive electrodes in a chemical cell?
• Anode = negative electrode
• Cathode = positive electrode
227
Why does the voltage reduce over time in a fuel cell?
The reactants in the chemical reaction get used up meaning voltage eventually reaches 0V
228
Half equation for oxidation at the anode in a chemical cell
(2)H2 → (4)H+ + (4)e-
229
Half equation for reduction at the cathode in a chemical cell
O2 + (4)H+ + (4)e- —> (2)H2O
230
How do fuel cells work?
As fuel enters the cell it becomes oxidised which sets up a potential difference across the wire
231
Calculate relative atomic mass of element isotopes
• Multiply isotopic abundance by mass of each isotope
• Add them together
• Divide by 100
232
Why can metals conduct electricity?
They contain delocalised electrons which are free to move and can carry charge
233
Why does aluminium tend to be extracted by electrolysis?
• Aluminium is more reactive than carbon
• So cannot by reduced by carbon
234
What range should reproducible results be within?
0.1 units
235
How can someone tell to stop adding a base to an acid when making a salt?
• When the solid remains in the beaker
• There is an excess of that base
• Meaning all the acid has reacted
236
How do you carry out simple distillation?
• Boil the water
• Condense water vapour in condenser
• Collect the water
237
Disadvantages of fuel cell
• Hydrogen needs to be stored however it’s flammable
• Expensige to manufacture
238
Indicators tend to be..
Weak acids
239
Before using a burette, what should be done first?
Rinse it with the solution going in burette
240
What should be placed at the bottom during a titration and why?
• A white tile
• This makes colour change easier to spot
241
What do we do to the conical flask to help the reactants react during a titration?
Swirl the flask regularly
242
Advantages of fuel cells
• Once set up, they require no maintenance
• Water is the only product
• Which can be used as drinking water
