Chemistry Paper Two Flashcards
What does the rate of reaction depend on?
Temperature
Concentration of a solution/pressure of gas
Surface Area
The presence of a catalyst
Why does temperature increase the rate of reaction?
When the temperature increases, the particles all move faster. As they move faster they collide more frequently.
Why does increasing the concentration or pressure increase the rate?
The solution is more concentrated, it means there are more particles knocking about in the same volume. Similarly when the pressure of a gas is increased it means that the same number of particles occupies a smaller space. This makes collisions between the reactant particles more frequent.
Why does increasing surface area increase the rate?
If one of the reactants is a solid, then breaking it up into smaller pieces will increase its surface area to volume ratio. This means that for the same volume of the solid, the particles, around it will have more area to work on- so there will be collisions more frequently.
What is Le Chatelier’s Principle?
The idea that if you change the conditions of a reversible reaction at equilibrium and the system will try to counteract that change.
What are alkanes?
Alkanes have C-C single bonds, the general formula is Cn H2n+2. They are saturated compounds, each carbon atom forms 4 single covalent bonds.
What are the properties of hydrocarbons?
They get less viscous as they get shorter.
The shorter the carbon chain, the more volatile the hydrocarbon is (easier to turn into a gas) so the lower the boiling point.
The shorter the carbon chain, the more flammable the hydrocarbon is.
What’s the equation of complete combustion of hydrocarbon with oxygen?
hydrocarbon + oxygen → carbon dioxide + water (+energy)
What is crude oil?
A fossil fuel, it’s formed from the remains of plants and animals, mainly plankton. Over millions of years with high temperatures and pressure, the remains turn into crude oil which can be drilled up.
How is crude oil separated?
The oil is heated until most of it has turned into a gas, this then enters the fractionating column.
The column is hotter at the bottom and cooler at the top.
The long hydrocarbons have high boiling points, so they condense so much quicker at the bottom.
The crude oil is then separated into different fractions, where the different fractions have a similar amount of carbon bonds.
What are alkenes?
Have a C = C bond. The general formula is CnH2n. They burn with smoky flames, when they combust completely.
What is the incomplete combustion for alkenes?
alkene + oxygen → carbon + carbon monoxide + carbon dioxide + water
What do alkenes do to bromine water?
When orange bromine water is added to a saturated compound, like an alkane, no reaction will happen and it will stay bright orange.
If it is added to an alkene the bromine will add across the double bond, making a colourless dibromo-compound so the bromine water is decolourised.
What happens to alkenes when steam is reacted?
Alcohols are formed. E.g ethene + water → ethanol
What are polymers?
Polymers are long molecules formed when lots of small molecules called monomers join together. This reaction is called polymerisation.
What are alcohols?
Alcohols have a -OH bond. They have the general formula CnH2n+1OH..
Alcohols are very flammable
What are carboxylic acids?
They have the functional group -COOH
They end in -anoic acid
They react with carbonates to produce a salt, water and carbon dioxide.
Can be made into esters: alcohol + carboxylic acid → ester + water.
What are amino acids? (Polymers)
An amino acid contains two different functional groups, a basic amino group (NH2) and a carboxyl group (COOH)
What is meant by purity?
Something that only contains one element or compound.
How do you test for chlorine?
Bleaches litmus paper, turning it white.
How do you test for oxygen?
Put a glowing splint inside a test tube, it will relight.
What is the test for CO2?
Turns limewater cloudy.
What is the test for hydrogen?
A flame will make a squeaky pop.
How do you test for carbonates?
Add a few drops of dilute acid, then connect this to limewater, it will turn cloudy if CO2 is present.
How to test for sulfates?
Add dilute hydrochloric acid as well as barium chloride to the mystery solution.
A white precipitate will form.
How to test for halides?
Add dilute nitric acid and silver nitrate solution.
Chloride gives a while precipitate.
Bromide gives a cream precipitate.
Iodide gives a yellow precipitate.
What are the different colours of flames in the flame test?
Lithium → Crimson Sodium → Yellow Potassium → Lilac Calcium → Orange-Red Copper → Green
What are the coloured precipitates with NaOH?
Calcium → White Copper → Blue Iron II → Green Iron III → Brown Aluminium → White but dissolves in NaOH and colourless Magnesium → White
What are alloys?
Made up by adding another element to the metal, this disrupts the structure making it a lot harder.
What are the 4 alloys used in everyday life?
Bronze = Copper + Tin
Brass = Copper + Zinc
Gold
Aluminium
What is the Haber Process?
Using hydrogen and nitrogen to make ammonia.
How is ammonia produced? (Haber Process)
Nitrogen is obtained from the air
Hydrogen comes from reacting natural gas with steam.
Reactants are passed over an iron catalyst at 450C and 200 atmosphere pressure.
This reaches equilibrium
Gas cools into a liquid and other things are recycled.
What are NPK fertilisers?
Fertilisers made from mainly nitrogen, phosphorus and potassium. Which increases the crop yield.
