practicals

Question 1

investigate solubility of a solid in water at a specific temperature

Answer 1

-choose a temperature e.g. 40
-heat the water to that temperature in a water bath/Bunsen burner with heat, until slightly over the temperature e.g. 43
-dissolve the compound in excess into the water
-leave the solution to cool to the exact temperature e.g. 40
-pour off some solution but not the solid
-find the mass of the of the evaporating basin and the solution
-heat the evaporating basin to evaporate all the water
-find the mass of the evaporating basin and solid
-the difference in the mass of solution and mass of solid is the total mass of solvent

solubility(g/100g) = (mass of solute/mass of solvent) x 100

Question 2

how to carry out a chromatography

Answer 2

1. draw start line in pencil
2. place spots of colourings on the start line
3. place paper in beaker with start line above solvent
4. place a lid on the beaker so the solvent does not evaporate from surface of the paper
5. when solvent almost reaches top of paper or solvent stops moving, stop the experiment
6. mark solvent front/where the solvent reached
7. leave to dry so that all the solvent evaporates

Question 3

practical to determine formula of a metal oxide by combustion

Answer 3

1. weight crucible and lid
2. place magnesium ribbon in crucible, replaced the lid and reweigh
3. calculate mass of magnesium
4. heat crucible with lid until the magnesium burns. Lid prevents magnesium oxide escaping ensuring accurate results
5. lift the lid from time to time to allow air to enter
6. stop heating when there is no sign of further reaction - constant mass
7. allow to cool and reweigh
   8.repeat for concordant results
8. calculate mass of magnesium oxide formed

Question 4

practical to determine formula of a metal oxide by reduction

Answer 4

1. place metal oxide in a tube side ways with a bunsen burner heating it
2. have a supply of methane with a bung coming into the tube, and burn of excess methane off the side of the tube
3. keep methane supply for a while after, as the metal will oxidise again otherwise
4. metal will be left in the tube
   CuO + CH4 -> Cu + CO2 +2H2O
   CuO + H2 -> Cu + H2O

Question 5

phosphorus and oxygen reaction

Answer 5

4P + 5O2 -> P4O10

Question 6

metal + acid observations

Answer 6

displace reaction
rapid fizzing, colour gas
metal disappears and floats around
heat produced

Question 7

Acid alkali titration

Answer 7

1. Use a pipette to transfer 25cm of sulfuric acid/HCl into a conical flask, on top of a white tile
2. Rinse burette with sodium hydroxide
3. Fill burette with sodium hydroxide
4. Make sure space between tap and tip contains liquid/no bubbles in the burette
5. Add drops of indicator e/g/ phenolphthalein
6. Add sodium hydroxide from the burette until the indicator changes colour permanently
7. Swirl the conical flask
8. Add sodium hydroxide dropwise close to the end point
9. Record initial and final volume on burette
10. Repeat until concordant results

Question 8

Experiment to prepare pure, dry sample of a soluble salt from an insoluble salt

Answer 8

1. heat acid in a beaker to speed up rate of reaction
2. Add base until in excess and stir with a glass rod
3. Filter the mixture using filter paper and funnel
4. Gently heat the filtered solution to evaporate some water
5. Until crystals form on a glass rod, shows hot saturated solution formed
6. Allow the solution to cool so that hydrated crystals form
7. Remove crystals by filtration
8. Dry by leaving in a warm oven

Question 9

Describe an experiment to prepare a pure dry sample of an insoluble salt, starting from two soluble reactants

Answer 9

1. Mix the two salt solutions together in a beaker
2. Stir with glass rod
3. Filter using filter paper and funnel
4. Wash with distilled water
5. Dry by leaving in a warm place

Question 10

Experiment for rates of reaction

Answer 10

Calcium carbonate + hydrochloric acid -> calcium chloride and water and carbon dioxide

Bung on top, tube going to an inverted measuring cylinder that is filled with water, inside a tray of water. See volume displaced at regular intervals.

Question 11

Decomposition of hydrogen peroxide

Answer 11

Hydrogen peroxide -> oxygen + water

Manganese oxide as a catalyst

Use inverted measuring cylinder method

Question 12

Effect of heat on ammonium chloride

Answer 12

-white solid ammonium chloride decomposes to ammonia and hydrogen chloride gas
-ammonia and HCl gas are both colourless, but they mix to form a white smoke
-they cool to form ammonium chloride again

Question 13

Dehydration of copper sulfate

Answer 13

Hydrated copper surface heats to form anhydrous copper sulfate and 5 water

Adding water to anhydrous copper sulphate forms hydrated copper sulfate again