Chemistry Triple 2 Flashcards
What colour is lithium in a flame?
Crimson
What colour is sodium in a flame?
Yellow
What colour is potassium in a flame?
Lilac
What colour is calcium in a flame?
Red
What colour is barium in a flame?
Green
How do you test for positive ions?
Flame test
How do you do the test for positive ions in a lab?
Dip clean wire loop into a sample of the compound and put in a bunsen flame
- loop should be really clean do this by dipping it in hydrochloric acid and rinsing it with distilled water
How do you find what metal is mixed with a metal hydroxide?
Add NaOH
Add a few drops of sodium hydroxide solution this would form and insoluble hydroxide and give you a coloured compound
What colour compound does calcium form?
White
What colour compound does copper form?
Blue
What colour compound does iron2+ form?
Green
What colour compound does iron 3+ form?
Brown
What colour compound does aluminium form?
White at first but the dissolves in excess NaOH to form a colourless solution
What colour compound does magnesium form?
White
How do you test for carbonates? ( negative ions)
Test for carbon dioxide as carbonate ions react with dilute acids to form carbon dioxide
- acid + carbonate = salt + water + carbon dioxide
How do you test for a halide? ( negative ions)
When you add silver ( AgNO3)
A precipitate should form
- chloride gives a white precipitate of silver chloride AgCl
- bromide gives a cream precipitate of silver bromide AgBr
- iodide gives a yellow precipitate of silver iodide AgI
How do you test for sulfate ions?
Add dilute HCL followed by barium chloride solution
- white precipitate of barium sulfate means the original compound was a sulfate
- Ba2+ + SO42- = BaSO4
What is a reversible reaction?
A reversible reaction is one where the products from the reaction can themselves react to produce the original reactants
What is a closed system?
None of the reactants or products can escape
What is an equilibrium?
Means that the amount if reactants and products will reach a certain balance and stay there
How do you change the position of the equilibrium?
Change temperature and pressure
Temperature?
- Increase the temperature, the endothermic reaction will increase to use up the extra heat
- decrease the temperature, the exothermic reaction will increase to give out more heat
Pressure?
- Increase pressure and it will encourage the reaction which produces less volume ( least molecules)
- decrease pressure it will encourage the reaction which produces more volume ( most molecules )
What does a catalyst do in a reaction?
- does not change the equilibrium
- speeds up the forward reaction and backward reaction by the same amount
- reaches equilibrium quicker
What is the haber process?
- Hydrogen and nitrogen are mixed
- Forward reaction is exothermic so low temperatures 450 degrees and high pressure so it favours side which has least molecules 3. Passed over iron catalyst so it reaches equilibrium quicker
- Cooled in condenser and liquid ammonia formed
- Waste nitrogen and hydrogen which doesn’t condense is recycled and used again
What is the compromise for pressure?
- high pressure 200 atm and high pressures it favours forward direction so more ammonia will be made and to get the highest % yield
- 200 atm as the higher the pressure the more expensive the equipment
What is the compromise for temperature?
The forward reaction is exothermic so it prefers low temperatures 450 degrees as if temperature is low there will be a slow rate of reaction
What is a homologous series?
Is a group of chemicals that react in a similar way because they have the same functional group
What is a functional group?
An atom or group of atoms that give organic compounds their characteristic reactions
What are the properties of the first three alcohols?
- flammable and produce carbon dioxide and water by burning in air
- reacts with sodium to give hydrogen and alkoxides
- ethanol is the main alcohol in drinks
- methanol causes blindness when drunk
- oxidation - ethanol is made in to ethanoic acid by microbes or chemical oxidising agents
- ethanoic acid is vinegar
What are the uses of alcohol?
- solvents - can dissolve substances that water cannot such as oil and fats
- perfume - ethanol is mixed with oil and water
- methylated spirit - ethanol with chemical and methanol added to it
What is methylated spirit used for?
Clean paint brushes and fuel
What are the disadvantages of methylated spirit?
Poisonous to drink- a purply die is added to it
What alcohol can be used as a fuel?
Ethanol
- it burns cleanly and it doesn’t smell
What are the advantages of alcohol being used at a fuel?
- can be mixed with petrol so it burns more cleanly so less pollution
- some countries have little oil but lots of sunshine so they grow lots of sugar cane which is renewable
What is the functional group of carboxylic acid?
- COOH
- there names end in anoic
How does carboxylic acid react with carbonates m?
They produce a salt water and carbon dioxide
What is the titration calculation?
C2= C1V2/V2
C1=C2V2/V1
Why do carboxylic acids produce and acidic solution when they dissolve in water?
When they dissolve they ionise and release H+ ions this makes the solution acidic
- they don’t ionise completely so only a weak acid is formed, this means they have a higher pH than other solutions of the same concentration which form stronger acids
What do you make when you oxidise ethanol?
ethanoic acid and water
What is ethanoic acid used for?
It can be dissolved in water to make vinegar which is used for flavouring and preserving food
Are carboxylic acids good for making soaps and esters?
Yes, carboxylic acids with long chains if carbon atoms are used to make soaps and detergents. Although they are s good solvent for many organic molecules they are not often chosen as they are too acidic
What is the functional group of esters?
- coo
What is an ester formed from?
An alcohol and a carboxylic acid
Alcohol + carboxylic acid = ester + water
What are the properties of an ester?
- smells nice and volatile so they are good for perfumes
- flammable
- don’t mix well with water as they are not very soluble
- do mix with alcohol and other organic solvents
What are esters used for?
Perfumes
Flavourings and aromas
Ointments
Solvents
What are the advantages and disadvantages of of esters?
- inhaling fumes from some esters irritates mucus membranes in the nose and mouth
- ester fumes are heavier than air and very flammable
- toxic in large doses
+ aren’t as volatile or as toxic as other organic solvents
What is exothermic?
Gives out energy to the surroundings - usually heat this is shown when the temperature rises
What is endothermic?
Takes in energy from the surroundings usually in the form of heat this is shown by a fall in temperature
Is a bond breaking exothermic or endothermic?
Endothermic
Is a bond forming exothermic or endothermic
Exothermic
How do you measure the energy difference?
Take temperatures of the two reagents and mix them in a polystyrene cup then measure the temperature of the solution at the end of the reaction
- amount of energy lost to the surroundings is the biggest problem
So you can reduce this by putting the polystyrene cup into a beaker of cotton wool to give more insulation and put a lid on it to reduce the energy loss by evaporation
In an endothermic reaction the energy required to break old bonds is …..
Greater than the energy released when new bonds are formed
In an exothermic reaction the energy released in bind forming is ….
Greater than the energy use in breaking old bonds
What is a calorimeter?
It can be used to compare the energy released by different fuels or different foods
How do you measure the energy transferred?
Energy transferred in (j)= mass of water (g) x 4.2 x temperature change
What are fuel consequences?
- effects the environment
- releases carbon dioxide which is a green house gas which causes global warming
- expensive to slow down the affects of climate change
- crude oil is running out so it will get more expensive and have a bigger economic impact
What does a catalyst do?
Lowers the activation energy
What is the activation energy?
The minimum energy needed to start off a reaction
What happens when you lower the activation energy?
The reaction happens more quickly and easily although the energy change for the reaction remains the same
What are the benefits and disadvantages of hydrogen?
+ very clean
- very explosive so you have to store it carefully
- special expensive engine
What is a fuel cell?
An electrical cell that is supplied with a fuel and oxygen and uses energy from the reaction between them to generate electricity
What are the benefits and disadvantages of a fuel cell?
+ doesn’t run out
+ doesn’t need charging
+ safer than nuclear
+ more practical than solar cells
How do you get energy from hydrogen and oxygen?
They produce water when they react
Its an exothermic reaction so they produce energy
You would get the energy by reacting hydrogen and oxygen in a combustible engine or a fuel cell
What effect has a fuel cell had on the car industry?
+ no greenhouse gases, nitrogen oxides, sulfur dioxide or carbon monoxide
- hydrogen has to be made from hydrocarbons from fossil fuels or electrolysis of water which uses energy
What is a fuel cell?
An electrical cell that is supplied with a fuel and oxygen and uses energy from the reaction to generate electricity
