Chemistry Laboratory Manual
1
Experiment 6
1.1 Types of chemical reactions
BACKGROUND
In chemistry there are many different types of chemical reactions. Chemists use chemical
equations as shorthand representations for reactions. The purpose of this experiment is to
observe several important types of chemical reactions and to write equations for these reactions.
EQUIPMENT REQUIRED
Balance
Spatula
Bunsen
Metal tongs
Wax taper
Dropper
Beaker (100ml)
Test tubes (one large fitted with rubber stopper and plastic gas delivery tubing, two small)
Steel wool
Zinc strips (two)
Copper strip (one)
Copper (II) carbonate (CuCO3) (2g)
Calcium carbonate (CaCO3) marble chips (2g)
Magnesium ribbon (two 3cm strips)
Silver nitrate solution (AgNO3) 0.1 mol L-1 (30ml)
Sodium bromide solution (NaBr) 0.1 mol L-1 (5ml)
Sodium hydroxide solution (NaOH) 0.1 mol L-1 (30ml)
Hydrochloric acid (HCl) 2 mol L-1 (10ml)
Hydrochloric acid (HCl) ).1 mol L-1 (30ml)
Limewater (Ca(OH)2) saturated (10ml)
Universal indicator (5 drops)
Lead (II) nitrate solution (Pb(NO3)2) 0.1 mol L-1 (25ml)
PROCEDURE
#1
Prepare a table including space for reactants, observations and products for the following
reactions.
Decomposition of a carbonate by heating
#2
Place a spatula of copper (II) carbonate into a large test tube and fit the test tube with a
stopper and delivery tube. Heat the test tube with a Bunsen and pass any gas evolved
through 5ml of limewater in another test tube.
Decomposition of a carbonate with an acid
#3
Place a spatula of calcium carbonate (marble chips) into a large test tube, add 2 mol L-1
hydrochloric acid to a depth of about 2 – 3 cm, and fit the test tube with the stopper and
delivery tube as before. Again note the effect of any gas evolved on limewater solution.
Oxidation of a metal
SAFETY NOTE
 Care must be taken when burning magnesium ribbon.
#4
a protective
mat on
bench. Cut a 3cm strip of magnesium ribbon.
 Place
Do not
look directly
atthe
thelaboratory
flame produced.
Hold the ribbon in some tongs and heat in a Bunsen flame above the mat.
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Chemistry Laboratory Manual
Reaction of a reactive metal with a dilute acid
#5
Place another 3cm of magnesium in a small test tube and add 2 mol L-1 hydrochloric acid
to a depth of about 3cm. note the reaction and collect any gas evolved in inverting
another small test tube and holding it directly about the reaction tube. Test the gas
evolved by placing a lighted taper in the inverted test tube.
Precipitation reactions
#6
Place 2-3 ml of 0.1 mol L-1 AgNO3 solution into a test tube and add the same volume of
0.1 mol L-1 NaBr solution.
#7
Place 2 – 3 ml of 0.1 mol L-1 CuSO4 solution into a test tube and add about the same
volume of 2 mol L-1 NaOH solution.
Metal displacement reactions
#8
Place about 25ml of 0.1 mol L-1 CuSO4 solution into a 100ml beaker and place into the
beaker a freshly cleaned zinc strip.
#9
Place about 25ml of 0.1 mol L-1 Pb(NO3)2 solution into a 100ml beaker and place into the
beaker a freshly cleaned zinc strip.
#10
Place about 25ml of 0.1 mol L-1 AgNO3 solution into a 100ml beaker and place into the
beaker a freshly cleaned copper strip.
Neutralisation reaction – reaction of an acid and a base
#11
Place about 20ml of 0.1 mol L-1 HCl into a beaker and add 5 drops of universal indicator.
Using a dropper gradually add 0.1 mol L-1 NaOH solution until about 25ml of the base
has been added. Note any colour changes which take place.
PROCESSING OF RESULTS AND QUESTIONS
1. Write word equations and balanced chemical equations for each of the reactions
observed.
2. Write word equations and balanced chemical equations for the following reactions.
a. Heating magnesium carbonate
b. Adding dilute sulphuric acid to copper (II) carbonate
c. Rusting of iron (or the burning of iron in pure oxygen)
d. Adding dilute sulphuric acid to calcium
e. Mixing solutions of barium nitrate and sodium sulphate to precipitate barium
sulphate
f. The reaction between lead and copper (II) sulphate to produce lead (II) sulphate
and copper metal
g. The reaction between sulphuric acid and potassium hydroxide solution to form
potassium sulphate and water.
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Chemistry Laboratory Manual
2
Experiment 7
2.1 Stoichiometric relationship between the quantities of substances in a
chemical reaction
BACKGROUND
Stoichiometry is concerned with the quantitative relationship between the amounts of substances
involved in chemical reactions. In this experiment you will obtain quantitative data from the
reaction between solutions of sodium iodide and lead (II) nitrate. This reaction produces a bright
yellow precipitate of lead (II) iodide, Pbl2.
This experiment is designed as a class activity. Different pairs of students will be provided with
the same mass of lead (II) nitrate but different masses of sodium iodide. The masses of lead (II)
iodide produced will be determined by weighing.
EQUIPMENT REQUIRED
Pre-weighed 1.66g samples of Pb(NO3)2 in 100ml beakers (one for each group)
Pre-weighed samples of NaI in 250 ml beakers (0.75, 0.90, 1.05, 1.20, 1.35, 1.50, 1.65, 1.80,
1.95, 2.10 g – one for each group
Filter funnel
Filter stand
Filter paper (Whatman No 1 – one 12.5 cm sheet)
Glass rod (two, one fitted with rubber ‘policeman’)
Balance
Oven at 110oC
Ethanol (5 ml)
Distilled water
PROCEDURE
#1
Copy the following table into your laboratory notebook.
Group
Number
1
2
3
4
5
6
7
8
9
10
Mass
Pb(NO3)2
1.66g
1.66g
1.66g
1.66g
1.66g
1.66g
1.66g
1.66g
1.66g
1.66g
Mass
NaI
0.75 g
0.90 g
1.05 g
1.20 g
1.35 g
1.50 g
1.65 g
1.80 g
1.95 g
2.10 g
Mass
Pbl2
Moles
Pb(NO3)2
5.0 x 10-3
Moles
NaI
5.0 x 10-3
Moles
Pbl2
SAFETY NOTE
 Lead salts are poisonous and must be handled with care.
 Make sure that the lead (II) nitrate does not come in contact with your skin.
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#2
Obtain your pre-weighed samples of Pb(NO3)2 and NaI.
#3
Add about 35ml of distilled water to both beakers and stir with a stirring rod to aid
dissolution. It may be necessary to gently warm the solutions to ensure that all the solids
dissolves.
#4
Carefully add the lead (II) nitrate solution to the sodium iodide solution. Rinse the empty
beaker three times with about 5 ml of distilled water to ensure complete transfer of the
lead (II) nitrate.
#5
Stir the mixture and allow it to stand for 5 – 10 minutes. Leave the glass rod in the
beaker.
#6
Weigh a filter paper and record its mass.
#7
Fold the filter paper and place it in a filter funnel in a filter stand. Moisten the filter paper
with a few drops of distilled water.
#8
Carefully filter the solution containing the precipitate, ensuring you make a quantitative
transfer to the filter paper. Use the glass rod to direct the precipitate into the paper.
#9
Rinse the walls of the beaker with about 5ml of distilled water and add the rinsings to the
filter paper. If precipitate adheres to the walls of the beaker use a glass rod with a rubber
‘policeman’ to detach the lead (II) iodide. Repeat the rinsing procedure with two more
5ml volumes of distilled water.
#10
After draining, wash the precipitate with about 5ml of ethanol and allow this to drain.
#11
Carefully remove the filter paper and place it in a labelled 100ml beaker.
#12
Place the beaker in a drying oven at 110oC and leave for about one hour.
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#13
Remove the beaker and paper and allow to cool. Reweigh the filter paper and precipitate
and record the mass.
PROCESSING OF RESULTS AND QUESTIONS
1. Write a balanced equation for the reaction.
2. Determine the mass of Pbl2 produced and enter in your results table. Collect and
tabulate all the class results.
3. Convert the masses given in the table into moles.
4. Plot a graph in which the number of moles of sodium iodide is plotted along the x – axis
and the number of moles of lead (II) iodide is plotted along the y – axis.
5. Describe in words what the graph shows and account for its shape.
6. For group numbers 1 – 5
a. Which reactant is present in excess?
b. Which is the limiting reactant?
7. For group numbers 7 – 10
a. Which reactant is present in excess?
b. Which is the limiting reactant?
Explain in terms of the reaction equation.
8. What is the mole ration Pb(NO3)2 : NaI for group number 6? Comment on the significance
of this ratio in relation to the shape of your graph.
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