All AQA Trilogy Chemistry paper 2

What is rate of reaction?

How quickly the reactant turns into the products

How to calculate mean rate of reaction?

Mean rate of reaction = quantity of (product formed/reactant used) / time taken

How to calculate rate of reaction with change in mass?

The reaction mixture is placed on a mass balance. As the reaction proceeds and the gaseous product is given off, the mass of the flask will decrease. The rate of reaction is then:

rate = change in the mass / time taken

How to calculate rate of reaction from the volume of gas produced?

The reaction mixture is connected to a gas syringe or an upside down measuring cylinder. The rate for the reaction is then:

Rate = volume of gas produced / time taken

What is the unit for rate of reaction?

g/s or cm(3)/s

What does a steep gradient mean in terms of rate of reaction?

High rate of reaction - the reaction happens quickly

What does a shallow gradient mean in terms of rate of reaction?

Low rate of reaction - the reaction happens slowly

How do you calculate mean rate between two points on a graph?

change in mass / change in time

How can you increase the rate of reaction via collision theory?

Increase the frequency of collisions or increase the energy of the particles when they collide

What is collision theory?

For a reaction to occur, the reactant particles need to collide. When the particles collide, they need to have enough energy to react or they’ll bounce apart.

What is activation energy?

The amount of energy that the particles must have for a reaction to occur

How can you increase the temperature of a reaction?

Heath the container in which the reaction is taking place (e.g. with a Bunsen burner)

How do you increase the conctration of a reaction?

Use a solution with more solute in the same volume of solvent

How do you increase pressure of gases in a reaction?

Increase the number of gas particles you have in the container or make the container smaller

How can you increase the surface area of solids in a reaction?

Cut the solid inti smaller pieces, or grinds it to create a powder, increasing the surface area as larger pieces decrease the surface area

How does increasing temperature increase rate of reaction?

1. The particles move faster, leading to more frequent collision

2. Particles have more energy, so more collisions result in a reaction

   Note: these are two separate effects

How will increasing the concentration of solutions increase the rate of reaction?

There are more reactant particles in the reaction mixture, so collisions become more frequent

How does increasing the pressure of gases increase the rate of reaction?

Less space between the particles means that there are more frequent collisions

How does increasing the surface area of solids increase the rate of reaction?

Only reactant particles on the surface of a solid are able to collide and react; the greater the surface area, the more reactant particles are exposed, leading to more frequent collisions.

What is a catalyst?

A substance that speeds up the rate of a reaction without being used up in the reaction.

How does a catalyst work?

a catalyst provides a different reaction pathway that has a lower activation energy. As such, more particles will collide with enough energy to react, so more collision result in a reaction.

What is a reversible reaction?

When the products can react to produce the original reactants

What is a closed system?

When no reactants or products can escape the reaction

What happens to a reversible reaction that is carried in a closed system?

It eventually reaches dynamic equilibrium - a point in time when the forward and backward reactions have the same rate

What is happening at dynamic equilibrium?

The reactants are still turning into the products, the products are still turning back into the reactants, the rates of these two processes are equal, so overall, the amount of reactants and products are constant

What do the conditions of a reaction refer to?

The external environment of the reaction

How can you change the conditions of a reaction in a closed system?

Changing the concentration of one of the substances, changing the temperature of the entire reaction vessel, changing the pressure inside the vessel

What does Le Chatelier’s principle state?

At equilibrium, the amount of reactants and products is constant. In order to change the amounts of reactant and product at equilibrium, the conditions of the reaction must be changed. The closed system will then counteract the change by favouring either the forward reaction or the backward reaction

How does decreasing the concentration of the product effect a reversible reaction and why?

It favours the forward reaction (equilibrium shifts to the right) - opposes the change by making less reactant and more product

How does increasing the concentration of the product effect a reversible reaction and why?

Favours the reverse reaction (equilibrium shifts to the left) - opposes the change by making more reactant and less product

What does effect of changing temperature depend on in a reversible reaction?

Which direction is endothermic and which direction is exothermic

How does an increase in the temperature of the surroundings effect a reversible reaction and why?

Favours the endothermic reaction - opposes the change by decreasing the temperature of the surroundings

How does a decrease in the temperature of the surrounding effect a reversible reaction and why?

Favours the exothermic reaction - opposes the change by increasing the temperature of the surroundings

How does increasing the pressure effect a reversible reaction and why?

Favours the reaction that results in fewer molecules - decreasing the number of molecules within the vessel opposes the change because it decreases the pressure

How does decreasing the pressure effect a reversible reaction and why?

Favours the direction that results in more molecules - increasing the number of molecules within the vessel opposes the change because it increases pressure

How will changing pressure effect a reversible reaction with the same number of molecules on each side?

No effect

What is crude oil originated from?

It is formed from the remains of ancient biomass - living organisms (mostly plankton) that died millions of years ago

What is raw crude oil?

A thick black liquid made of a large number of different compounds mixed together. Most compounds are hydrocarbons of various sizes.

What is a hydrocarbon?

A substance made up of only carbon and hydrogen

Why are hydrocarbons used as fuels?

When they react with oxygen, they release a lot of energy. This is called combustion.

What is complete combustion?

A type of combustion where the only products are carbon dioxide and water

What is flammability?

How easily a substance burns

Do long or short chain hydrocarbons have greater flammibility?

Short chain hydrocarbons

What is boiling point?

The temperature at which a substance boils

Do long or short chain hydrocarbons have a higher boiling point?

Long chain hydrocarbons

What is viscosity?

How thick a substance is

Do long or short chain hydrocarbons have a greater viscosity?

Long chain hydrocarbons

What are alkanes?

A family of hydrocarbon molecules that only have single bonds

What are the first four alkanes in order?

Methane, ethane, propane, butane

What is the molecule formula of alkanes?

C(n)H(2n+2)

What is fractional distillation?

A process in which different hydrocarbons in crude oil are seperated into fractions based on their boiling point

What is similar about all the molecules in a fraction of the fractional distillation column?

They have a similar number of carbon atoms, and so a similiar boiling point

Describe the process of fractional distillation

1. Crude oil is vapourised (turned into a gas via heating)

2. They hydrocarbon gases enter the column

3. They hydrocarbon gases rise up the column

4. As hydrocarbon gases rise up the column, they cool down

5. When the different hydrocarbons reach their boiling points in the column, they condense

6. The hydrocarbon fraction is collected

What are the products of fractional distillation?

Refinery/Petroleum gas (short-chain hydrocarbons and low boiling point alkanes, used as fuel), gasoline/petrol (used for fuel in car engines), Kerosene (used for aircraft fuel), Diesel oil/gas oil (used as fuel in diesel engines and as boiler fuel), residue (very thick, sticky mixture of long-chain hydrocarbons, used in making road and flat roofs)

What fuels come from crude oil?

Petrol, diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases

What useful materials are produced from crude oil?

Solvents, lubricants, polymers, and detergents

How is feedstock formed by the separation of crude oil?

Fractions form the raw material for other processes and the production of other substances

What are alkenes?

A family of hydrocarbons that contains double bonds between carbon atoms

Are alkanes or alkenes more reactive?

Alkenes

How can we test for alkenes?

Alkenes turn bromine water from orange/brown to colourless

What can alkenes be used for?

Fuels, to produce polymers, and many other materialsWh

What is catalytic cracking?

When the hydrocarbons are vapourised, then passed over a hot catalyst

What is steam cracking?

Hydrocarbons are mixed with steam at a very high temperature

What is a pure substance?

A substance that contains a single element or compound that isn’t mixed with any other substance