Chemistry Practicals

Measure 30 cm3 of 1 mol dm⁻ 3 ethanoic acid and transfer to a conical flask. 2. Attach conical flask to gas syringe or use collection over water method (see previous page) 3. Measure the mass of a weighing bottle with approximately 0.05 g of calcium carbonate 4. Add the calcium carbonate to the conical flask- quickly resealing the bung so no gas escapes 5. Measure the final total volume of gas 6. Reweigh the empty weighing bottle test tube from step 3 7. Repeat the experiment several more times, increasing the mass of calcium carbonate by about 0.05 g each time.

Irritant - dilute acid and alkalis- wear googles Corrosive- stronger acids and alkalis wear goggles Flammable – keep away from naked flames Toxic – wear gloves- avoid skin contact- wash hands after use Oxidising- Keep away from flammable / easily oxidised materials

Weigh the sample bottle containing the required mass of solid on a 2 dp balance • Transfer to beaker • Reweigh empty sample bottle • Record the difference in mass Pour solution into a 250cm3 graduated flask via a funnel. • Rinse beaker and funnel and add washings from the beaker and glass rod to the volumetric flask. • make up to the mark with distilled water using a dropping pipette for last few drops. • Invert flask several times to ensure uniform solution

• Pipette 25cm3 of original solution into a 250cm3 volumetric flask • make up to the mark with distilled water using a dropping pipette for last few drops. • Invert flask several times to ensure uniform solution.

In many experiments the best method for measuring mass is 1. Measure mass on 2 or 3d.p. balance of a weighing bottle with the required quantity of solid in it 2. Empty mass into reaction vessel/flask 3. Reweigh the now empty weighing bottle 4. Subtract the mass of the empty weighing bottle from the first reading to give exact of mass actually added.

Lithium : Scarlet red Sodium : Yellow Potassium : lilac Rubidium : red Caesium: blue Magnesium: no flame colour (energy emitted of a wavelength outside visible spectrum) Calcium: brick red Strontium: red Barium: apple green

Use a nichrome wire ( nichrome is an unreactive metal and will not give out any flame colour) Clean the wire by dipping in concentrated hydrochloric acid and then heating in Bunsen flame If the sample is not powdered then grind it up. Dip wire in solid and put in Bunsen flame and observe flame

Calcium hydroxide is classed as partially soluble in water and will appear as a white precipitate.Magnesium Hydroxide is insoluble in water and appears as a white precipitate.Strontium and barium salts will not form a hydroxide precipitate on addition o sodium hydroxide due to their high solubility.

Testing for Ammonium ions (NH4 a) Place about 10 drops of 0.1 mol dm–3 ammonium chloride in a test tube. b) Add about 10 drops of 0.4 mol dm–3 sodium hydroxide solution. Shake the mixture. c) Warm the mixture in the test tube gently using a water bath. d) Test the fumes released from the mixture by holding a piece of damp red litmus paper in the mouth of the test tube.

BaCl2 solution acidified with hydrochloric acid is used as a reagent to test for sulphate ions. If acidified Barium Chloride is added to a solution that contains sulfate ions a white

Fluorides produce no precipitate Chlorides produce a white precipitate Ag+ (aq) + Cl- (aq)  AgCl(s) Bromides produce a cream precipitate Ag+ (aq) + Br- (aq)  AgBr(s) Iodides produce a pale yellow precipitate Ag+ (aq) + I- (aq)  AgI(s

Use a fume cupboard because of toxic HCl fumes as they are corrosive Avoid inhaling vapours Product of distillation is flammable Wear eye protection

Remove the bung at intervals for 20 mins to release the pressure Pressure is released to release volatile compounds

Helps with better separation allowing for organic layer to be at the top and inorganic at the bottom

To remove unreached moles of HCl and also open the tap to give off pressure

Provides a surface for bubbles to form Enables smaller bubbles to form To prevent larger bubbles from forming

1)Hydrogen may escape from the apparatus Use a sealed apparatus with a gas syringe 2)Magnesium ribbon covered with oxide Clean with abrasive before weighing 3) The mass of magnesium is too small to be measured by the balance available Use more precise balance