Chemistry Paper 2 Flashcards
What is the formula for a mean rate of reaction in terms of reactants?
quantity of reactant used/time taken
What is the formula for a mean rate of reaction in terms of products?
quantity of reactant product formed/time taken
How can you measure the quantity of a reactant or product?
In grams or in cm3
What are the two possible units for rate of reaction?
g/s or cm3/s (where s is seconds)
How could you measure the rate of a reaction from a graph?
Draw a tangent to the curve and calculate the gradient.
What is “collision theory”?
The theory that chemical reactions only occur when particles collide with sufficient energy
What five factors can affect the rate of a reaction?
Temperature, surface area of a solid, concentration of reactants in solution, pressure of gases, catalyst
State the effect of increasing the surface area on the rate of a reaction
Increases the rate
Explain why increasing the surface area increases the rate of a reaction
More particles are available to collide there are therefore more frequent collisions between reactants.
State the effect of increasing the concentration on the rate of reaction
Increases
Explain why increasing the concentration increases the rate of reaction
More concentrated means more particles in solution, therefore more frequent collisions between reactants.
State the effect on increasing the pressure of a gas on the rate of reaction
Increases
Explain why increasing the pressure of a gas increases the rate of a reaction
Less space for the particles to move around in, therefore more frequent collisions
State the effect of increasing the temperature on the rate of reaction
Increases
What is the activation energy?
The amount of energy a particle needs before it will be able to react when it collides with another particle
Explain why increasing the temperature increases the rate of reaction
Increases the speed at which particles move therefore more frequent collisions.
Increases the number of particles which have the activation energy therefore more collisions result in a reaction.
What is a catalyst?
Something which changes the rate of a reaction but is not used up in that reaction
How do catalysts speed up reactions?
They provide another route for the reaction to take place which has a lower activation energy.
What is a reversible reaction?
A reaction which can go from reactants to products but also from products to reactants
What chemical symbol represents a reversible reaction?
⇌
If a reaction is exothermic in the forward direction what will it be in the reverse direction?
Endothermic
What is dynamic equilibrium?
The point in a reversible reaction when the forward and reverse reactions are occurring at the same rate
How is the amount of reactant changing at equilibrium?
It is not changing
How is the amount of product changing at equilibrium?
It is not changing
(HT) What is Le Chatelier’s principle?
When a reaction at equilibrium is changed, it will seek to counteract that change
(HT) A reaction is exothermic in the forward direction. What will occur if the temperature is increased?
The backward reaction will increase as it is endothermic and will reduce the temperature
(HT) A reaction is at equilibrium when some product is removed. What will occur?
The forward reaction will increase as that will increase the amount of product
(HT) How does increasing the pressure affect equilibrium?
Favours the side with fewer gaseous molecules
What is crude oil?
A mixture of hydrocarbons
What is a finite resource?
One that will run out
Why is crude oil a finite resource?
Because it takes longer to form than the rate at which we are using it up
What is a hydrocarbon?
A compound made of atoms of carbon and hydrogen only
What is a general formula?
A mathematical formula which allows you to work out the chemical formula of a substance
What is an alkane?
A hydrocarbon with only single bonds
Name the first four alkanes
Methane, ethane, propane, butane
What is the general formula for alkanes?
Cn + H2n+2
How does boiling point change with the length of an alkane?
The longer the alkane, the higher its boiling point
How does viscosity change with the length of an alkane?
The longer the alkane, the more viscous (the thicker) it is
How does flammability change with the length of an alkane?
The longer the alkane, the less flammable it is
What is fractional distillation?
A process used to separate mixtures substances with different boiling point
What are the steps involved in fractional distillation?
Crude oil is vaporised, different molecules rise up the fractionating column and cool down. Condense at different points on the column.
Why is fractional distillation important?
Because the different fractions have different uses
What is a fuel?
A substance which when reacted with oxygen releases energy
Name five fuels we obtain from crude oil
Petrol, diesel, kerosene, heavy fuel oil and liquefied petroleum gases
What other uses are there for products of fractional distillation?
Solvents, lubricants, polymers and detergents
What is combustion?
The reaction of a fuel with oxygen
What are the products of complete combustion?
Carbon dioxide and water
When does incomplete combustion occur?
When there is not enough oxygen present
What is cracking?
The process of breaking down a long hydrocarbon into smaller hydrocarbons
What are the products of cracking?
Short alkanes and alkenes
Why is cracking important?
Because smaller hydrocarbons are more useful than longer ones
What are the two types of cracking?
Catalytic and steam cracking
What are alkenes
A different type of hydrocarbon which is more reactive than an alkane
What are alkenes used for?
As a starting material to make more useful chemicals
How do you test for an alkene?
React it with bromine water
What is the colour change when an alkene reacts with bromine water?
Turns from orange to colourless
What is chemical analysis?
The process of establishing what chemicals are present in a substance
In everyday language what is a “pure” substance?
A substance that has had nothing added to it and is in its “natural” state
In chemistry what is a “pure” substance?
A substance made of a single element or compound
How can pure substances be distinguished from impure ones?
By their melting/boiling points
Describe the melting and boiling points of pure substances
One very specific temperature
Describe the melting and boiling points of impure substances
They change state at a range of temperatures
What is a formulation?
A complex mixture designed as a useful product
Give three examples of formulations
Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods
What is chromatography?
A process to separate the constituents of a mixture
In paper chromatography, what is the stationary phase and what is the mobile phase
Paper is stationary, solvent (usually water or ethanol) is mobile
How can chromatography show the difference between pure and impure substances?
Pure ones will not separate into a number of spots
How is the Rf value calculated?
Distance moves by spot/ distance moved by solvent
What does a substance’s Rf value depend on?
How soluble it is in the solvent
In chromatography, why must the substances be placed on a pencil line?
Pencil will not dissolve in the solvent
In chromatography why must the solvent height be lower than the pencil line
So that the substance does not into the solvent off the paper
How can hydrogen be tested for?
Makes a squeaky pop when a splint is placed in it
How can oxygen be tested for?
Relights a glowing splint
How can carbon dioxide be tested for?
Buble through limewater, turns it milky (cloudy)
How can chlorine be tested for?
Bleaches damp litmus paper white
What is the approximate proportion of nitrogen in Earth’s current atmosphere?
80%
What is the approximate proportion of oxygen in Earth’s current atmosphere?
20%
Which gases are in small proportions in the current. atmosphere?
Noble gases, water vapour, carbon dioxide
When Earth was formed which planets was its atmosphere similar to?
Venus and Mars
What do Mars and Venus’s atmospheres comprise of?
Carbon dioxide with little or no oxygen
What produced the gases present in Earth’s early atmosphere?
Volcanoes
Which gases were present in Earth’s early atmosphere?
Carbon dioxide water vapour and nitrogen with small amount of methane and ammonia
Why have theories about Earth’s early atmosphere developed and changed over time?
Evidence is limited and it was billions of years ago
By what process do algae and plants produce oxygen?
Photosynthesis
Write the word equation to represent photosynthesis
carbon dioxide + water -› oxygen + glucose
How did the world’s oceans form?
The Earth’s temperature cooled, causing water vapour in the air to condense
How did the oceans reduce atmospheric levels of carbon dioxide in Earth’s early atmosphere?
Carbon dioxide dissolved in the oceans
How did algae and plants reduce levels of carbon dioxide in Earth’s early atmosphere?
By photosynthesising
What was formed when shells of organisms made using dissolved carbon dioxide fell to the bottom of the ocean and were covered and compressed?
Sedimentary rock
What was formed when plants that grew millions of years ago died and were trapped and compressed under rocks?
Coal
What was formed when plankton that lived in the ocean millions of years ago died and were trapped and compressed under rocks?
Crude Oil and Natural Gas
Name three greenhouse gases
Water Vapour, Carbon Dioxide, and Methane
Describe the wavelength of radiation that comes from the sun and is reflected by the Earth
From the Sun: short wave,
From the Earth: long wave
What happens to the long wave radiation that is reflected from the Earth in the atmosphere?
It is absorbed by greenhouse gases
What is the name given to the process that warms up the surface of the Earth?
The greenhouse effect
What human activities increase carbon dioxide levels?
Deforestation and burning fossil fuels
What human activities increase methane levels?
Farming animals and landfill
What is the name given to the increasing average temperature of the Earth?
Climate Change
Name an effect of climate change
Increased flooding, changes in rainfall patterns, frequency of storms, amount of water in a habitat etc…
What is the name given to the total amount of carbon dioxide and other greenhouse gases emitted over the full lifecycle of a product, service or event?
Carbon footprint
What is produced from the complete combustion of a hydrocarbon fuel?
Carbon dioxide and water
Which products could be produced from an incomplete combustion of a hydrocarbon fuel?
Carbon dioxide, water, carbon monoxide, carbon particulates
Which gas is produced when fuels are burned and contain sulfur impurities?
Sulfur dioxide
Which gases are produced when nitrogen and oxygen react in the very high temperatures of a car engine?
Oxides of nitrogen
What are the effects of carbon monoxide?
A toxic gas
What are the effects of sulfur dioxide?
Causes respiratory problems and acid rain
What are the effects of the oxides of nitrogen?
Causes respiratory problems and acid rain
What are the effects of particulates of fuels?
Cause global dimming and health problems for humans
What do humans use resources for?
Warmth, shelter and food
What are finite resources?
Resources that will run out
What is sustainable development?
Development that meets the needs of the current generations without compromising the ability of future generations to meet their own needs
Give an example of a natural product that has been replaced by a synthetic product
Cotton has been replaced by polyester
What is potable water?
Water that is safe to drink
In the UK how is potable water produced?
Passing fresh water through filter beds and sterilising
How is water sterilised?
Using chlorine, ozone or ultraviolet light
What is desalination?
Removal of salt from sea water
In what two ways can desalination be carried out?
Reverse osmosis or distillation
What is the main disadvantage of desalination?
It requires a large amount of energy
In what kinds of locations is desalination carried out?
Ones where there is limited supply of fresh water
What needs to be removed from sewage and agricultural waste water?
Organic matter and harmful microbes
What needs to be removed from industrial waste water?
Organic matter and harmful chemicals
How is sewage treated?
Screening, sedimentation, anaerobic digestion, aerobic biological treatment
(HT) Name two new ways of extracting copper from low-grade ores
Phytomining and bioleaching
(HT) What is a low grade ore?
Rock with only a small amount of metal compound in it
(HT) How is phytomining carried out?
Plants absorb metal compounds, are harvested and then burned to produce ash
(HT) How is bioleaching carried out?
Bacteria are used to produce a leachate solution
(HT) How can copper be produced from the products of phytomining or bioleaching?
Electrolysis or displacement with scrap iron
What is a life cycle assessment?
A way of assessing the environmental impact of a product across its entire life cycle
What are the four stages in a product’s life cycle?
Extracting and processing raw materials, manufacturing and packaging, use and operation, disposal distribution at each stage.
Why is it important to reduce use, recycle and reuse products?
Reduces the use of limited resources, energy sources and environmental impacts
Give an example of a product that can be reused
Glass
Give an example of a product that can be recycled
Metal
