Preparation of Reagents

Preparation of solutions for mandatory experiments and specified demonstrations

Safety note

It is essential to be familiar with the hazards associated with the particular chemicals used to make up each of the solutions needed. The following Department of Education and Science publications are particularly useful;

· ‘Safety in School Science’ (second edition 2002)

· ‘Safety in the School Laboratory’ (second edition 2002).

Another very useful resource in this regard is the ‘Chemistry Mandatory Experiments’ CD-ROM produced by the Leaving Certificate Chemistry Support Service, under the auspices of the Physical Science Initiative.

Preparation of reagents

Distilled or deionised water should be used in making up all of these solutions.

Chapter 1

Page 11 – specified demonstration

All necessary reagents can be used as purchased.

Chapter 3

Page 32 – specified demonstration

All reagents needed can be used as purchased.

Chapter 4

Page 42 – mandatory experiment

All necessary reagents can be used as purchased.

Page 45 – specified demonstration

All necessary reagents can be used as purchased.

Chapter 5

Pages 71 to 74 – mandatory experiment

Chlorine solution:

Add 100 cm3 of commercial bleach to 500 cm3 of water. In a fume-cupboard, add concentrated hydrochloric acid drop by drop, with constant stirring, until a drop of the solution is just acid to litmus. This solution must be freshly prepared.

Bromine solution:

In a fume-cupboard, shake 0.5 cm3 bromine with 100 cm3 water. Store in a tightly stoppered brown bottle.

Iodine solution:

Dissolve 20 g of potassium iodide in 500 cm3 of water. Add about 10 g of iodine crystals, dissolve and make up to 1 litre with water.

Sodium chloride solution (approximately 0.2 M):

Dissolve about 12 g sodium chloride in water and make up to 1 litre with water.

Sodium bromide solution (approximately 0.2 M):

Dissolve about 20 g sodium bromide in water and make up to 1 litre with water.

Potassium iodide solution (approximately 0.2 M ):

Dissolve about 33 g potassium iodide in water and make up to 1 litre with water.

Iron(II) sulfate solution (approximately 0.2 M):

Dissolve 11.2 g of iron(II) sulfate crystals in 100 cm3 of water containing 2 cm3 of concentrated sulfuric acid, and dilute to 200 cm3 with water. This solution must be freshly prepared.

Iron(III) chloride solution (approximately 0.2 M):

Dissolve 11 g of hydrated iron(III) chloride in 100 cm3 of water containing 4 cm3 of concentrated hydrochloric acid, and dilute to 200 cm3 with water.

Sodium sulfite solution (approximately 0.2 M):

Dissolve 5.2 g of sodium sulfite in 100 cm3 of water, and dilute with water to 200 cm3. This solution must be freshly prepared.

Sodium hydroxide solution (approximately 1 M):

Dissolve 10 g of sodium hydroxide pellets in 200 cm3 of cold water and make up to 250 cm3 with water.

Silver nitrate solution (approximately 1 M):

Dissolve 4 g of silver nitrate crystals in water, and make up to 250 cm3 with water. Store in a brown bottle. This solution is best freshly prepared and in very small quantities.

Barium chloride solution (approximately 0.2 M):

Dissolve about 40 g barium chloride in water, and make up to 1 litre with water.

Dilute hydrochloric acid solution (approximately 2 M):

In a fume-cupboard, add about 170 cm3 of concentrated hydrochloric acid slowly, with stirring, to about 500 cm3 of water, and make up to 1 litre with water.

Dilute ammonia solution (approximately 3 M):

In a fume-cupboard, dilute 40 cm3 of concentrated ammonia solution to 250 cm3 with water.

Pages 75 to 77 – mandatory experiment

Acidified copper(II) sulfate solution (approximately 0.1 M):

Dissolve 5 g of hydrated copper(II) sulfate (CuSO4.5H2O) in about 100 cm3 water and make up to 200 cm3 with water. Carefully add 20 cm3 of concentrated sulfuric acid.

Page 78 – specified demonstration

2 M hydrochloric acid solution:

In a fume-cupboard, add about 170 cm3 of concentrated hydrochloric acid slowly, with stirring, to about 500 cm3 of water, and make up to 1 litre with water.

Page 81 – specified demonstration

0.5 M sodium sulfate solution:

Dissolve 161 g of hydrated sodium sulfate (Na2SO4 .10H2O) in enough water to make 1 litre of solution.

Page 82 – specified demonstration

0.5 M potassium iodide solution:

Dissolve about 83 g potassium iodide in water and make up to 1 litre with water.

Chapter 6

Pages 94 to 97 – mandatory experiment

Part (a)

Sodium carbonate solution (approximately 0.5 M):

Dissolve 143 g of hydrated sodium carbonate (Na2CO3.10H2O) in water to make 1 litre of solution.

Sodium hydrogencarbonate solution (approximately 0.5 M):

Dissolve 42 g of sodium hydrogencarbonate in water to make 1 litre of solution.

Dilute hydrochloric acid (approximately 3 M):

In a fume-cupboard, add 255 cm3 of concentrated hydrochloric acid slowly, with stirring, to about 500 cm3 of water, and make up to 1 litre with water.

Limewater:

Add about 200 g of calcium hydroxide to 2.5 litres of water. Shake vigorously at intervals over a period of time and finally allow to settle. Decant off the clear limewater solution from above the undissolved solids. Top up the container with water and repeat the process.

Magnesium sulfate solution (approximately 0.25 M):

Dissolve 15.4 g of hydrated magnesium sulfate (MgSO4.7H2O) in enough water to make 250 cm3 of solution.

Part (b)

Sodium sulfate solution (approximately 0.1 M):

Dissolve 32.2 g of hydrated sodium sulfate (Na2SO4 .10H2O) in enough water to make 1 litre of solution.

Sodium sulfite solution (approximately 0.5 M):

Dissolve 126 g of hydrated sodium sulfite (Na2SO4 .10H2O) in enough water to make 1 litre of solution.

Barium chloride solution (approximately 1 M):

Dissolve about 240 g barium chloride in water, and make up to 1 litre with water.

Dilute hydrochloric acid (approximately 3 M):

In a fume-cupboard, add 255 cm3 of concentrated hydrochloric acid slowly, with stirring, to about 500 cm3 of water, and make up to 1 litre with water.

Part (c)

Sodium chloride solution (approximately 0.1 M):

Dissolve 5.85 g of sodium chloride in enough water to make 1 litre of solution.

Silver nitrate solution (approximately 0.1 M):

Dissolve 4 g of silver nitrate crystals in water, and make up to 250 cm3 with water. Store in a brown bottle. This solution is best freshly prepared and in very small quantities.

Dilute ammonia solution (approximately 3 M):

In a fume-cupboard, dilute 40 cm3 of concentrated ammonia solution to 250 cm3 with water.

Part (d)

Potassium nitrate solution (approximately 0.1 M):

Dissolve 10.1 g of potassium nitrate in enough water to make 1 litre of solution.

Iron(II) sulfate solution:

Dissolve 140 g of iron(II) sulfate crystals in 300 cm3 of water containing 5 cm3 of concentrated sulfuric acid, and dilute to 500 cm3 with water. This solution must be freshly prepared.

Part (e)

Disodium hydrogenphosphate(V) solution (approximately 0.03 M):

Dissolve 11.81 g of disodium hydrogenphosphate(V) in enough water to make 1 litre of solution.

Ammonium molybdate reagent:

Dissolve 4.5 g of ammonium molybdate [(NH4)6Mo7O24.4H2O] crystals in a solution made from 4 cm3 0.88 ammonia solution and 6 cm3 deionised water. Add to this 12 g ammonium nitrate. Dilute with deionised water to 100 cm3 in a volumetric flask. Immediately before use, acidify with 1.5 cm3 of concentrated nitric acid per 10 cm3 ammonium molybdate solution.

Page 102 – specified demonstration

All necessary reagents can be used as purchased.

Page 104 – mandatory experiment

All necessary reagents can be used as purchased.

Page 106 – specified demonstration

All necessary reagents can be used as purchased.

Chapter 8

Page 126 – specified demonstration

All necessary reagents can be used as purchased.

Page 127 – specified demonstration

All necessary reagents can be used as purchased.

Page 128 – specified demonstration

All necessary reagents can be used as purchased.

Page 145 – mandatory experiment

All necessary reagents can be used as purchased.

Chapter 11

Page 185 – mandatory experiment

All necessary reagents can be used as purchased.

Page 192 – mandatory experiment

Hydrochloric acid solution (approximately 0.2 M):

In a fume-cupboard, add about 17 cm3 of concentrated hydrochloric acid, with stirring, to about 500 cm3 of water, and make up to 1 litre with water. Stopper, and mix thoroughly.

0.1 M sodium carbonate solution:

Using a balance, measure accurately 10.6 g of pure anhydrous sodium carbonate on a clock glass. Transfer to a beaker containing about 200 cm3 of deionised water. To ensure that all the sodium carbonate is transferred, use a wash bottle to rinse the clock glass with deionised water, and add the rinsings to the beaker. Stir the mixture with a stirring rod until the sodium carbonate has fully dissolved. Using a wash bottle, wash off the solution on the stirring rod with deionised water into the beaker. Pour the solution through a clean funnel into a 1 litre volumetric flask. Using a wash bottle, rinse out the beaker several times with deionised water, and add the rinsings to the solution in the flask. Rinse the funnel with deionised water, allowing the water to run into the flask. Carefully make up the volume to 1 litre with deionised water. Stopper the flask and invert it several times to ensure a homogeneous solution

Page 194 – mandatory experiment

0.1 M hydrochloric acid solution:

Use ampoules of 1 M HCl and dilute 10 cm3 to 100 cm3 with deionised water.

Sodium hydroxide solution (approximately 0.1 M):

Dissolve 4 g of sodium hydroxide pellets in 50 cm3 of cold water and make up to 1 litre with water.

Page 198 – mandatory experiment

0.1 M sodium hydroxide solution:

Use ampoules of 1 M NaOH and dilute 10 cm3 to 100 cm3 with deionised water.

Page 201 – mandatory experiment

0.1 M hydrochloric acid solution:

Use ampoules of 1 M HCl and dilute 10 cm3 to 100 cm3 with deionised water.

Chapter 12

Page 216 – mandatory experiment

0.1 M ammonium iron(II) sulfate solution:

Weigh accurately 39.2 g of ammonium iron(II) sulfate crystals in a small beaker and dissolve them in a small amount of dilute sulfuric acid. Transfer the solution to a 1000 cm3 volumetric flask. Wash out the beaker with deionised water and add the washings to the volumetric flask. Add about 200 cm3 of dilute sulfuric acid to the volumetric flask and then bring the total volume to 1 litre using deionised water. The bottom of the meniscus should be resting on the mark. Stopper the volumetric flask and invert several times.

Potassium manganate(VII) solution (approximately 0.02 M):

Dissolve about 3.2-3.25 g of potassium manganate(VII) in about 1 litre of deionised water, and allow the solution to stand overnight. Filter the solution through glass wool in a funnel. The solution should be stored under cool conditions in a clean dark glass bottle.

Dilute sulfuric acid (approximately 1.5 M):

Add 85 cm3 of concentrated sulfuric acid slowly to about 700 cm3 of deionised water containing about 20 ice cubes. Stir the mixture, and make up the volume with water to 1 litre in a volumetric flask. Stopper the volumetric flask and invert several times.

Page 218 – mandatory experiment

Potassium manganate(VII) solution:

Potassium manganate(VII) is not a primary standard. It is therefore not possible to make up solutions of exact concentration directly from the solid reagent. Instead a solution must be made up of approximately the required concentration and standardised prior to use. The potassium manganate(VII) solution for this experiment can be standardised in mandatory experiment 4.5.

An approximately 0.005 M solution of potassium manganate(VII) solution may be made up as follows:

Measure out 1.58 g of potassium manganate(VII) into a beaker. Add about 500 cm3 of deionised water. Stir and warm gently to dissolve the crystals. Pour the solution into a 2 litre volumetric flask. Add more water to the beaker to dissolve any remaining crystals of potassium manganate(VII). Transfer the solution formed, with washings, to the volumetric flask. Repeat this process until all crystals have been dissolved and transferred to the volumetric flask. Carefully fill the flask to the calibration mark with deionised water. Stopper the flask and shake to ensure a homogeneous solution.

1.5 M sulfuric acid solution:

Page 221 – mandatory experiment

0.02 M potassium iodate solution:

Add 4.28 g potassium iodate to about 600 cm3 water in a beaker, and stir to dissolve. Transfer the solution to a 1000 cm3 volumetric flask. Wash out the beaker with deionised water and add the washings to the volumetric flask. Then bring the total volume to 1000 cm3 using deionised water. Stopper the volumetric flask and invert several times.

0.5 M potassium iodide solution:

Dissolve 83 g potassium iodide in water and make up to 1 litre with water.

Dilute sulfuric acid:

Add 56 cm3 of concentrated sulfuric acid slowly to about 700 cm3 of deionised water containing about 20 ice cubes. Stir the mixture, and make up the volume with water to 1 litre in a volumetric flask. Stopper the volumetric flask and invert several times.

Sodium thiosulfate solution (approximately 0.12 M):

Dissolve 30 g of sodium thiosulfate in boiled deionised water and make the solution up to 1 litre using a volumetric flask. To increase the stability of the solution add 0.1 g of sodium carbonate.

Starch indicator solution:

Pour, with stirring, a paste containing 1 g starch and a little cold water into 100 cm3 of boiling water. Boil for two minutes, and allow to cool. The solution should be stored in stoppered bottles.

Page 223 – mandatory experiment

0.l M sodium thiosulfate solution:

Dissolve 15.8 g of anhydrous sodium thiosulfate in boiled deionised water and make the solution up to 1 litre using a volumetric flask. To increase the stability of the solution, add 0.1 g of sodium carbonate.

Dilute sulfuric acid:

Starch indicator solution:

Pour, with stirring, a paste containing 1 g starch and a little cold water into 100 cm3 of boiling water. Boil for two minutes, and allow to cool. The solution should be stored in stoppered bottles.

Chapter 13

Page 241 - specified demonstration

Methane:

Natural gas, if available, can be used, as it contains methane. Otherwise, liquid petroleum gas (LPG), which contains propane and butane, which have similar solubility properties to those of methane, can be used.

Ethene:

Ethene can be prepared from ethanol, as described on page 338.

Ethyne:

Ethyne can be prepared from calcium dicarbide as described on page 243.

Page 243 – mandatory experiment

Acidified copper(II) sulfate solution: