Practicals

Investigating solubility at a specific temperature

Investigating solubility at a specific temperature

• Method: Place a water-filled beaker in a water bath to control the temperature, then add solid until it stops dissolving

• Independent variable: Temperature using water bath

• Dependent variable: Time taken for solid to stop dissolving

• Control variable: mass of salt crystals

• Hazard control: Use heatproof gloves to avoid burning

investigating chromotography

• Method: Draw pencil line on chromatography paper above water level in the beaker, then place dots of food colourings along the baseline

• Independent variable: Dyes

• dependent variable: distance dye has travelled, number of dyes, RF value

• Control variable: volume of water

• hazard/precautions: Draw baseline using pencil lead as it is soluble, do not draw baseline beneath water level else it will wash away

Combustion of magnesium to form magnesium oxide to determine formula of magnesium oxide

• Method: Measure mass of crucible and magnesium ribbon. place crucible over bunsen burner and lift lid frequently to allow complete combustion. Measure the mass of magnesium oxide.

• Dependent variable: Mass of magnesium oxide, magnesium ribbon

• Safety precaution: Orange safety flame, use tongs to avoid burns

Electrolysis of sodium chloride

• Method: Set up electrochemical cell and connect to crocodile clips and wire. Fill beaker with sodium chloride solution. Turn on the power and record observation

• Make sure sandpaper is used on electrodes to get rid of solids on electrodes.

• Precaution: Keep room well ventilated as chlorine gas is toxic

Investigating reactions between dilute hydrochloric acid and metals

• Method: Fill up measuring cylinder with water and place upside down in a water trough. Add acid and metal to conical flask and immediately add rubber bung attached with delivery tube. Measure the volume of water before and after to work out the volume of gas produced.

• Results: Magnesium is fastest, then zinc, and iron is the slowest

• Precaution: Acid is corrosive so wear safety goggles

Preparing a salt

• Method: Fill the beaker with boiling water, then add sulfuric acid into the boiling tube placed in the beaker. Add the copper (II) oxide. Lift and gitate/shake the mixture then resubmerge, repeating until all copper oxide is added. Replace the water with freshly boiled water and leave for five minutes. Filter out the unreacted copper oxide and use filtrate of copper sulfate solution and boil the solution on a crystallising dish, wash with deionised water and dry.

• Precautions: Wash conical flask with deionised water first to ensure all copper sulfate solution is transferred. Reduce time on bunsen burner as anhydrous copper sulfate may be produced

Preparing lead sulfate

• Method: Add potassium sulfate into beaker with lead nitrate and stir until precipitate forms. Filter. Use deionised water to wash solid left in beaker over filter paper and remove potassium nitrate. Leave in evaporating dish then dry in oven. Lead sulfate is insoluble so it can be removed by filtration

• Precaution: Lead sulfate is toxic so wash hands immediately

Temperature change in a displacement reaction

• Method: Place polystyrene cup in a beaker and fill the gap with cotton wool. Add copper sulfate, record starting temperature with thermometer. Add Magnesium then put lid on. Record higher temp reached and use q = mc delta t

Investigate the effect of concentration of hydrochloric acid and the surface area of marble chip have on rate of reaction

• Method: Use a measuring cylinder and add HCl. Fit cotton wool in the opening to avoid evaporation. Measure mass. Remove cotton wool, add marble chips, replace cotton wool. Record new mass. repeat with different HCl concentration and make sure mass of marble chip is constant (vice versa if measure SA). Calculate amount of reactants used over time

• Precaution: use fume cupboard if gas given off is toxic

effect of catalysts on decomposition of hydrogen peroxide

• Method: Add hydrogen peroxide to flask, connect gas syringe to bung using delivery tube (at 0cm³). Add manganese (IV) oxide. Measure volume of gas produced. Repeat with same volume and conc, but with different catalyst (such as copper oxide)

• Precaution: catalysts must have the same mass and bung must be attached