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Equilibrium

The equilibrium will try to minimise any changes you make

TEMPERATURE

all reactions are exothermic in one direction and endothermic in the other direction. If youincrease the heat in a reaction then the equilibrium will try to counteract this by reducing the heat through moving towards the endothermic side of the reaction

PRESSURE

changing this will only affect equilibium involving gasses. If you increase the pressure of the reaction the equilibrium will try and reduce this by moving towards the direction where there are fewer moles of gas

CONCENTRATION

if you increase the concentration of the reactants by adding more of either of them then the eqilibrium will try to decrease this by moving it towards the right and making more of theproduct

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Preparing insoluble salts

Precipitation reactions make insoluble salts - you just need to pick the right reactants and then mix them together.

STAGE 1 - add one spatula of lead nitrate to a test tube and fill it with distilled watershakethoroughly to ensure it's dissolved then add potassium iodide. Using distilled water ensures there are no extra ions. tip the two soloutions into a small beaker and stir it making sure it's mixed. the salt should precipitate out.

STAGE 2 - fold a piece of filter paper into a filter tunnel and put it into a conical flask. pour the formed soloution into the beaker slowly so nothing spills. swill out the beaker with distlled water and pour that onto the filter paper so you get all the product

STAGE 3 - Rinse the contents of the filter paper with distilled water to make sure that all thesoluble salts have been washed away. scrape the lead iodide onto some fresh filter paperand leave it to dry. 

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Contact process

Step 2 is a reversible reaction so the conditions can be altered to get the right balance of equilibrium

2 SO2 + O2 ⇌ 2 SO3

TEMPERATURE - Oxidising sulfure dioxide to form sulfur trioxide is an exothermic reaction, so to get more product the temperature should be reduced which would shift it to the right, but this would slow downt he reaction. a compromise of 450' is used

PRESSURE - There are two moles of product compared to three moles of reactant. so to get mroe product pressure should increase to move it towards the right. but increasing pressure is expensive and equilibrium is already on the right so its not necessary - meaningatmposheric pressure (1 atmosphere) is used

CATALYST - to increase the rate of the reaction a catalyst of vanadium pentoxide is used which doesnt effect the equilibrium

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Titrations

Titrations allow you to find out how much acid is needed to neutralise a quantity of alkali (or vice versa) This is the method:

  • using a pipette and a pipette filler, add some alkali (Usually 25 centimetres cubed) to a conical flask, along with two or three drops of indicator
  • Fill a burette with acid. make sure you do this with below eye level so that your not looking upwards if some acid spills.
  • using a burette, add the acid to the alkali a bit at a time - giving the conical flask aregular swirl so that the indicator is reacting properly.
  • Go a lot slower when the volume is reaching close the result from the rough titration.
  • the indicator changes color when all the alkali/acid has been neutralised 
  • record the volume and that is the result
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