Chemistry Practicals Flashcards
CP1-Measure the molar vol of a gas
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.
CP1-What are some safety and hazards?
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
CP2-Make a volumetric(standard solution)
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
CP2-How to dilute a 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.
CP2-Measuring Mass Accurately
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.
CP7-Flame Tests
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
CP7-How to carry out a Flame Test
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
CP7-Group 2 results
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.
CP7-Testing for ammonium ions
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.
CP7:Testing for presence of Sulfate Ions
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
CP7-Testing for presence of halide ions with silver nitrate.
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
