Expirements

Question 1

How to make a pure, dry sample of a soluble salt (acid and insoluble base method)?

Answer 1

1) Heat the acid in a water bath - speeds up the reaction. In a fume cupboard to avoid releasing acid fumes.
2) Then add the insoluble base to the acid. They will react to produce a soluble salt and water. You know when the base in excess when all the acid has been neutralised because the excess solid will sink to the bottom of the flask.
3) filter the excess solid using a filter paper and and funnel. So that the solution is only salt and water.
4) Heat the solution gently using a Bunsen burner to evaporate the water until the first few crystals start to form
5) Leave the solution to cool and allow the salt to crystallise.
6) Rinse the crystals with distilled water and dab them dry with a paper towel

Question 2

How to carry out titration?

Answer 2

1. Use the pipette and pipette filler to put the acid into the conical flask
2. Stand the conical flask on a white tile
3. Clamp the burette vertically in the clamp stand. There should be just enough room underneath for the conical flask and tile
4. Make sure the burette tap is closed and use as small funnel to carefully fill the burette with the acid slightly above the Ocm3 line.
5. Put 5-10 drops of phenolphthalein indicator into the conical flask and swirl
6. Then open the tap to fill the jet, then take the initial reading of the burette to 2d.p
   TAKE A ROUGH TITRATION FIRST
7. Carefully open the tap so the acid flows into the flask at a constant rate
8. Constantly swirl the flask when adding the acid
9. When there is a sudden colour change, it is the end point of the reaction.
10. Read the burette scale carefully to 2d.p and record the volume of acid you added

Question 3

How to carry out chromatography?

Answer 3

1. Spots of ink or plant dye are placed on a pencil line
2. As the paper is lowered into the solvent, some of the dye spreads up the paper
3. The paper has absorbed the solvent, and the dye has spread further up the paper

Question 4

How to measure change in rate of reaction using color change?

Answer 4

1) Add a set volume of dilute sodium thiosulfate to a conical flask
2) Place the flask on a piece of paper with a black cross drawn on if. Add some dilute HCI fo the flask and start the stopwatch
3) Watch the black cross disappear through the cloudy sulfur and time how long it takes.
4) The reaction can be repeated with solutions of either reactant at different concentration. The depth of the liquid must be the same each time
5) The higher the concentration the faster the rate of reaction.
Subjective and only has one data point

Question 5

How to measure the effect of changing the temperature on the rate of a reaction by the mass change?

Answer 5

1. Add a set volume of dilute hydrochloric acid to a conical flask and carefully place on a mass balance
   2) Add some magnesium ribbon to the acid and quickly plug the flask with cotton wool
   3) start the stopwatch and record the mass on the balance. Take readings at regular intervals
   4) Plot the results in a table and work out the mass list from each reading
   5) repeat with more concentrated solutions.

Question 6

How to investigate the variables that affect temperature changes in reacting solutions?
liquids

Answer 6

1. Place the polystyrene cup inside the glass beaker to make it more stable.
2. Measure an appropriate volume of each liquid, eg 25 cm3.
3. Place one of the liquids in a polystyrene cup.
4. Record the temperature of the solution.
5. Add the second solution and record the highest or lowest temperature obtained.
6. Change your independent variable and repeat the experiment. Your independent variable could be the concentration of one of the reactants, or the type of acid/alkali being used, or the type of metal/metal carbonate being used.`

Question 7

How to investigate the variables that affect temperature changes in reacting solutions?
solids

Answer 7

1. Place the polystyrene cup inside the glass beaker to make it more stable.
2. Measure an appropriate volume of the solution, eg 25 cm3.
3. Measure an appropriate mass of the solid, or select a suitable sized piece of metal.
4. Place the solution in a polystyrene cup.
   Record the temperature of the solution.
5. Add the solid and record the highest or lowest temperature obtained.
6. Change your independent variable and repeat the experiment. Your independent variable could be the surface area of the solid, or the type of acid being used, or the type of metal being used.