Chemistry (Paper 1) Flashcards
Who developed the periodic table?
Dmitri Mendeleev
Who created the Billiard Ball Model?
Dalton
What model did JJ Thompson propose?
The plum pudding model
Who created the Bohr model?
Rutherford
What type of elements are involved in ionic bonding?
A metal and non metal
Relative mass of an electron
0
What is an ion?
A charged atom
What type of bonding involves only non metals?
Covalent bonding
Ionic bond definition
Electrostatic attraction between oppositely charged ions (when electrons are transferred from metal atoms to non metal atoms)
Electrostatic force
A force of attraction between particles with opposite charges
What is filtration?
Method that separates an insoluble solid from a liquid
Ionic compounds exist as
Giant ionic lattices
Electricity definition
A flow of charge
Why do ionic lattices have high melting and boiling points?
Large amounts of energy is required to break the strong ionic bonds
Why do ionic lattices only conduct electricity when liquid or dissolved in water
The ions are free to move and so charge can flow through the structure.
The number of electrons an atom needs to get a full outer shell in covalent bonding is equal to
the number of bonds that an atom can form
Intermolecular force
A force between molecules
Weak intermolecular forces are overcome when..
simple molecular structures melt or boil
Simple molecular structures have no
overall charge
Covalent bond definition
Shared pair of electrons (between non metals)
Simple molecular structures are usually liquids or gases because
the intermolecular forces are so weak, not much energy is required
small molecules have a low boiling point whilst large molecules have a higher boiling point because..
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
What element is diamond, graphite and fullerene made of?
Carbon
Polymers are
Long chain of molecules held together by strong covalent bonds
Why are polymers solid at room temperature?
The intermolecular forces are relatively strong.
Polyatomic ions definition
• Ions made from more than one charged atom (and are covalently bonded together)
• Eg Nitrate (NO3 -)
Formula for Nitrate
NO3-
Sulfate formula
SO4 2-
Hydroxide formula
OH-
Carbonate formula
CO3 2-
Ammonium formula
NH4 +
Pure metals are (soft/hard)
Soft
Alloys are (soft/hard)
Hard
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)
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
Molecule definition
Atoms chemically bonded together
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
Allotrope definition
A different structural form of an element eg Diamond and Graphite
What does PANIC stand for?
Positive Anode, Negative Is Cathode
Graphene
• A single layer of graphite
• Used for drug delivery or in electronics
Properties of transition metals (1)
• Less reactive than group 1 metals
• shiny and malleable
• sonorous
• electricity and heat conductor
Properties of transition metals (2)
• catalysts for chemical reactions
• form coloured compounds
• high melting and boiling points
• able to have different charges
Electroplating definition
Using electrolysis to coat an object in a thin layer of a metal
What is electroplating used for?
To protect objects from corroding or to improve its appearance
What is the structure of a metal?
A lattice of positive metal ions attracted to delocalised electrons
Alloy definition
Mixture of a metal with small amounts of other elements
What elements are found in steel?
Iron (main element) and carbon
What elements are found in brass?
Copper (main element) and zinc
What elements are found in bronze?
Copper (main element) and tin
What elements are found in an aluminium alloy (aka magnalium)
Aluminium (main element) and magnesium
Corrosion definition
Destruction of a material by reaction with oxygen
Rusting definition
Corrosion of iron or steel
Electrolyte definition
an ionic compound that is dissolved in water and conducts electricity during electrolysis
Positive electrode
Anode
Negative electrode
Cathode
Why do solid ionic compounds not conduct electricity?
Their ions aren’t free to move therefore charge is unable to flow through the structure
What is zinc beneficial for?
killing bacteria
How does sacrificial protection work?
When a more reactive metal is used to coat a metal so that it corrodes instead
Empirical formulae meaning
The simplest whole number ratio of atoms or ions in a substance
How are chemical reactions sped up?
By heating them
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
Concentration equation
Mass/Volume
Negative ion
Anion
Methods for corrosion prevention
Electroplating and sacrificial protection
unit for concentration
g dm-3
Law of conservation of mass
The mass of reactants and products are the same in a reaction
Mole meaning
Unit for measuring the number of particles
Relationship between a mole and Avogadro’s constant
1 mole of a substance contains 6.02 x10^23 particles of that substance
RFM meaning
Relative formula mass (sum of atomic masses of the elements in the molecule)
How can the concentration of a solution be increased?
•Increasing the mass of the solute • decreasing volume of solvent
Concentration definition
How much solute is dissolved in a volume of solvent
Equation to work out the Mass of a substance
Mr x moles
1 dm3 =
1L or 1000cm3
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
1 ton = how many grams
1,000,000 grams
1 mg = how many grams
1/1000 grams
1 mole of a substance weighs the same as
the Ar or Mr of the substance (in grams)
What are the 4 separation techniques?
filtration, crystallisation, distillation and chromatography
Crystallisation
• To make crystals out of a solution by evaporating it
• Separates a soluble salt from a solution
How to calculate percentage yield
Actual yield / theoretical yield x 100
Toxic meaning
Something that causes death
Why are reagents used in excess?
To ensure all of the other reactant reacts
What does reagent mean?
Reactant
Limiting reagent meaning
A reagent not in excess that limits how much product is made
Yield definition
The mass of product produced by a chemical reaction
Stoichiometry meaning
Ratio of moles that react
Why do some reactions produces a small yield?
• Unwanted side reactions
• Incomplete reactions
• Product left behind on apparatus
What are the diatomic elements?
hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), and iodine (I)
What is concentration measured in (using moles)?
Mol/dm³
Equation to work out moles (from the concentration of a solution)
Concentration x volume
Unit for measuring volume
dm³
How do you carry out a titration?
An accurate method to measure the concentration of acids and alkalis
How are titrations carried out?
Measure the volume of an acid in a burette needed to exactly neutralise an alkali (which has been measured into a conical flask with a pipette)
How to calculate atom economy %
(Mr of desired product \ Mr of all products) x 100
How to calculate volume (Avogadro’s law)
24 x moles
What is Avogadro’s Law?
1 mole of any gas (at room temperature and pressure) has a volume of 24 dm³
[Topic 3]
State symbol for aqueous
aq
What makes a solution acidic?
Positive hydrogen ions (H+)
Bases meaning
Substances which can neutralise an acid, forming a salt and water
Alkali meaning
A base that can dissolve in water to produce hydroxide ions in a solution
What are the most common bases?
• Metal oxides eg CaO
• Metal hydroxides eg Ca(OH)2
• Metal carbonates CaCO3
What substance do alkalines produce in water?
Negative hydroxide ions (OH-)
Wasp stings are
Basic
Bee stings are
Acidic
What are indicators?
Substances that change colour when added to an acid or alkali
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
How does the phenolphthalein indicator function?
In an acidic solution: It’s colourless
In an alkaline solution: It turns pink
How does a methyl orange indicator function?
In an acidic solution: It turns red
In an alkaline solution: It turns yellow
How can pH be measured?
• Universal Indicator solution • Digital pH meter
Apparatus used in a titration
• Bunsen burner • Burette • Glass pipette • Indicator • Conical flask • Acid and alkali
What are common acids?
• Sulfuric acid (H₂SO₄)
• Hydrochloric acid (HCL)
• Nitric acid (HNO₃)
Symbol equation for dissolved hydrochloric acid
HCL (aq) —> H+(aq) + Cl-(aq)
Symbol equation for dissolved sodium hydroxide (Alkali)
NaOH (aq) —> Na+(aq) + OH-(aq)
What does green indicate on a universal indicator?
The substance is neutral
What happens when an acid reacts with an alkali
Neutralisation occurs • The H+ ions react with OH- ions to produce water
Word equation and ionic equation for the reaction between an acid and alkali
Acid + alkali —> salt + water
H+ + OH- —> H2O
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
Chemical formulae for acids
Sulfuric acid - H₂SO₄
Nitric acid - HNO₃
Hydrochloric acid - HCl
Ethanoic acid - CH₃COOH
Common salts
Sulfates
Chlorides
Nitrates
Phosphates
Ethanoates
Citrates
Common alkalis and their formulae
Ammonia NH3
Calcium hydroxide Ca(OH)₂
Dilute acids have
Few H+ ions in the solution
Concentrated acids have
Lots of H+ ions in the solution
What happens when acids dissolve in water?
They ionise (separate into ions) to release hydrogen ions in the solution
What makes an acid strong?
When the molecules ionise fully
What makes an acid weak?
When the molecules only ionise partially
In a weak acid, the reaction is ________
Reversible
Ionic equation for weak acids
HX ⇌ H+ + X-
How is pH value calculated?
Using the concentration of hydrogen ions in a solution
What would decreasing the pH of a solution by 1 do?
It would increase the concentration of H+ ions by a factor of 10
Metal + acid —>
Salt + hydrogen
Metal oxide + acid —>
Salt + water
Metal hydroxide + acid —>
Salt + water
Metal carbonate + acid —>
Salt + water + carbon dioxide
Ammonia + acid—>
Ammonium salt
Test for hydrogen
When a lit splint goes out with a squeaky pop
Test for carbon dioxide
When you bubble the gas through limewater and it turns cloudy white
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
When a solution ends in -ate what does it contain?
Oxygen
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
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)
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
Substances soluble in water
• Sodium, potassium and ammonium compounds (carbonates and hydroxides)
• All nitrates
• Most chlorides
• Most sulfates
• Calcium hydroxide
Substances insoluble in water
• Silver chloride
• Lead chloride
• Lead sulfate
• Barium sulfate
• Calcium sulfate
• Most carbonates
• Most hydroxides
Zinc ion formula
Zn (2+)
Oxide ion formula
O (2-)
Nitride ion
N (3-)
Electrolysis meaning
The breakdown of an ionic compound using electricity
The electrolyte must be..
Molten or in an aqueous solution
Positive ion
Cation
Negative ion
Anion
Why can electrolytes only conduct electricity when molten or in solution
The ions are free to move therefore charge can flow
How is indicator paper used to determine the pH of a mixture?
• Look at the colour of the indicator
• Compare it to the chart
When the air hole of a Bunsen burner is open, the flame is
a roaring blue flame
Methane (CH4) exists as a
simple molecule
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
OILRIG acronym
• Oxidation is Loss
• Reduction is Gain
What word is used to remember the process that occurs at the anode?
Anox
(Anode oxidation)
What word is used to remember the process that occurs at the cathode?
Redcat
(Reduction cathode)
Half equation for chlorine
2Cl - -> Cl2 + 2e -
Half equation for zinc ion
Zn2+ + 2e - -> Zn
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
Half equation for oxygen produced in the electrolysis of an aqueous solution
4OH - —> 2H2O + O2 + 4e-
What process happens at the anode?
Oxidation (losing electrons)
What process happens at the cathode?
Reduction (gaining electrons)
Observation at anode during electrolysis of copper sulfate solution
The electrolyte bubbles (oxygen is present)
Observation at cathode during electrolysis of copper sulfate solution
Red-brown solid (copper)
Why must the electrodes be inert?
So that the electrodes themselves do not react with the ions in the solution
Inert meaning
Unreactive
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
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
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
What steps are required before weighing the copper electrodes?
• Clean with emery paper
• Dip into acetone
Test for oxygen
A glowing splint relights when placed in a test tube
Fullerene
• Graphene rolled into a tube/sphere
• Simple molecule
• Conducts electricity
• Used as a lubricant or in drug delivery
Where are metals found?
In rocks in the Earth’s crust
What is an ore ?
A rock containing metal
What are metals called when they are found in their natural form?
- Uncombined or native
- They are unreactive metals
What is distillation?
A process used to separate liquids based on their boiling points
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
What is chromatography?
A method used to separate a mixture of soluble substances
Two phases of chromatography
• Stationary phase (where the molecules can’t move)
• Mobile phase (where the molecules can move)
Difference between the 2 types of distillation
Fractional distillation can separate liquids with similar boiling points whereas simple distillation can’t
The reactivity of a metal is related to
its tendency to form positive ions and react with oxygen
Why do we react metals with acid sometimes?
They are not reactive enough to react with water
What substances are used to determine the reactivity of a metal?
• Water
• Acid
Metal + Oxygen —>
Metal Oxide
Metal + Acid —>
Salt + Hydrogen
Metal + Water —>
Metal Hydroxide + Hydrogen
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
Tendency meaning in terms of reactivity
How readily a metal forms ions
Which metals do not react with water or acid?
• Copper
• Silver
• Gold
What is a redox reaction?
A reaction where one substance is reduced and another is oxidised
Metal extraction methods
• Heating with carbon
• Electrolysis
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
General equation for reduction with carbon
Metal oxide + Carbon —> Metal + Carbon dioxide
Why is heating by carbon a better option compared to electrolysis?
It’s cheaper as it uses less energy
Types of bonds and structures
• Ionic —> Ionic lattice
• Covalent —> Giant covalent/Polymers/Simple molecules
• Metallic —> Metals (metallic lattice)
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
Why can graphite can act as a lubricant?
Layers can slide over each other due to the weak forces between them
Diamond characteristics
• Giant covalent lattice
• Doesn’t conduct electricity as it has no free electrons
• Very hard
• Used in drill bits or jewellery
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
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
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
What is a life cycle assessment?
An assessment that calculates the environmental impact of the stages in a product’s life
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)
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
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
High grade ore definition
Rock that contains a high percentage of metal
Low grade ore definition
Rock that contains a low percentage of metal
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
Alternative metal extraction methods
• Phytomining
• Bioleaching
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
What does bioleaching involve?
Bacteria feeding on low grade ores to produce a solution of copper ions (leachate)
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
Disadvantage of bioleaching
It’s very slow
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
Disadvantage of phytomining
Its slow
How is ammonia produced?
• Using the Haber process where:
• Temperature = 450°C
• Pressure = 200 atm (atmospheres)
• Catalyst = Iron
What is ammonia mainly used for?
Making fertiliser
What is the balanced symbol equation for ammonia production
N2 + (3)H2 ⇌ (2)NH3
How is nitrogen obtained?
In the air
How is hydrogen obtained?
Natural gas
Dynamic equilibrium meaning
The forward and backward reactions are both happening at the same rate (reversible reactions)
What does a simple cell consist of?
• 2 electrodes made of metals with different reactivities
• An electrolyte (salt solution/ acid)
(typically KOH)
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
What are the negative and positive electrodes in a chemical cell?
• Anode = negative electrode
• Cathode = positive electrode
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
Half equation for oxidation at the anode in a chemical cell
(2)H2 → (4)H+ + (4)e-
Half equation for reduction at the cathode in a chemical cell
O2 + (4)H+ + (4)e- —> (2)H2O
How do fuel cells work?
As fuel enters the cell it becomes oxidised which sets up a potential difference across the wire
Calculate relative atomic mass of element isotopes
• Multiply isotopic abundance by mass of each isotope
• Add them together
• Divide by 100
Why can metals conduct electricity?
They contain delocalised electrons which are free to move and can carry charge
Why does aluminium tend to be extracted by electrolysis?
• Aluminium is more reactive than carbon
• So cannot by reduced by carbon
What range should reproducible results be within?
0.1 units
How can someone tell to stop adding a base to an acid when making a salt?
• When the base remains in the beaker
• There is an excess of that base
• Meaning all the acid has reacted
How do you carry out simple distillation?
• Boil the water
• Condense water vapour in condenser
• Collect the water
Disadvantage of fuel cell
Hydrogen needs to be stored however it’s flammable
Indicators tend to be..
Weak acids
Before using a burette, what should be done first?
Rinse it with the solution going in burette
What should be placed at the bottom during a titration and why?
• A white tile
• This makes colour change easier to spot
What do we do to the conical flask to help the reactants react during a titration?
Swirl the flask regularly
