PART 4
Industrial Chemistry
2015
1
2
Overview
Focus Experiment Dot Point
number
2
22
identify data, plan and perform a first-hand investigation to model an
equilibrium reaction
23
choose equipment and perform a first-hand investigation to gather
information and qualitatively analyse an equilibrium reaction
Perform first-hand investigations to observe the reactions of sulfuric acid
acting as an oxidising agent and a dehydrating agent
3
24
4
25
identify, plan and perform a first-hand investigation to identify the products
of the electrolysis of an aqueous solution of sodium chloride
5
26
perform a first-hand investigation to gather information and describe the
properties of a named emulsion and relate these properties to its uses
27
perform a first-hand investigation to carry out saponification and test the
product
28
perform a first-hand investigation to demonstrate the effect of soap as an
emulsifier
perform a first-hand investigation to assess risk factors and then carry out a
chemical step involved in the Solvay process, identifying any difficulties
associated with the laboratory modelling of the step
6
29
3
Experiment 22
Identify data, plan and perform a first-hand investigation to model an equilibrium reaction
MODELLING EQUILIBRIUM
INTRODUCTION
Many chemical reactions go to completion so the reactants have been completely consumed, for
example burning a match. Some chemical reactions are reversible and so the products react to form
the reactants again. The relationship between reactants and products can be investigated through
modelling.
AIM
To plan and perform an investigation to model an equilibrium reaction.
EQUIPMENT
2 x 500 mL 1 x 250 mL, 1 x 100 mL beakers
2 rulers
2 large containers with vertical sides such as tote boxes to hold water
2 different coloured food dyes
CHEMICALS
Nil
RISK ASSESSMENT
Nil
METHOD
1 Remember for equilibrium to be established you need to have a closed system.
2 You can use the beakers to transfer water between two tote boxes so representing the forward
and reverse reactions. Use two different dyes to colour the water in the boxes—one to represent
reactants and the other products. (red and blue work well)
3 Fill the tote boxes with different amounts of water, e.g. 5 L in one and 8 L in the other and label
them 1 and 2.
4 The amount of water in each tote box can be compared by measuring the depth of water.
5 Start by using two 500 mL beakers. Lie the beakers on their sides in the water (see diagram)
simultaneously dip one into tote box 1 and the other into tote box 2 then pour the contents of
each of the beakers into the opposite bowl. Mix the colours in each box well.
6 Note the change in the colour of the water in each of the boxes and make regular measurements
of the depth of water in each box, e.g. every 10 transfers.
7 Consider how you will determine when equilibrium has been reached (note the colour and depth
of the water in the boxes).
8 Refill the bowls and repeat using two different sized beakers.
9 Draw up a results table to record the number of dips, the colour of the water and the depth of the
water.
4
RESULTS
CONCLUSION
QUESTIONS
1
How did you determine that equilibrium had been reached?
2
What did you notice about the colour of water in each of the boxes?
3
What do you think the results would have been if all the water had been in one box at the
beginning—would the results have been different?
4
What effect did using two different sized beakers have on the equilibrium?
5
What do using two different beakers represent in terms of rate of forward and reverse
reaction?
6
Discuss any limitations of this model.
5
EXPERIMENT 23
EQUILIBRIUM IN GASES
INTRODUCTION
Many reactions proceed almost to completion. In reactions that do not proceed to completion the
products of the reaction begin to react to reform the reactants until the rates of the forward and
backward reaction are equal. When such a situation exists a state of chemical equilibrium has been
achieved. In fact all chemical reactions are reversible to some extent, but in many cases the
reactions go to completion.
With a reversible reaction it is possible to alter the relative proportions of products and reactants by
altering one of the factors which affect the state of equilibrium. The effect of such changes can be
predicted using le Chatelier’s Principle.
In this experiment the equilibrium that occurs between the brown gas nitrogen dioxide and the
colourless gas dinitrogen tetroxide will be investigated
2NO2 (g)
N2O4 (g) +
Brown
colourless
57kJ
Because NO2 (g) is brown and N2O4 (g) is colourless it is possible to observe qualitatively the effect
of various changes on the relative proportions of reactants and products
EQUIPMENT
3 Large transparent glass syringes with sealed ends
Hot tap water bath at about 60oC
Ice bath
CHEMICALS
Gas mixture of NO2/N2O4 in glass syringes
RISK ASSESSMENT
What is the risk
Why is it a risk?
How will you minimise the
risk?
METHOD
This experiment will be carried out as a demonstration.
a. Effect of pressure or volume on equilibrium
1. Observe the colour intensity of the gas mixture in the syringe
2. Push the gas syringe quickly so that the volume occupied by the gas mixture is
instantaneously reduced. Note the immediate change in colour of the gas mixture.
6
3. Carefully observe the change in colour intensity which occurs over several seconds after
the immediate colour change. Record your results in a table. Remember the relationship
between pressure and volume .
b. Effect of temperature on the equilibrium
1. Compare the colour of the two flasks containing the NO2 (g)/ N2O4 (g) mixtures
2. Place one of the flasks in the ice bath, leave for a few seconds and compare this flask with
the flask at room temperature
3. Remove the flask from the ice bath and place it in hot water. Leave a few seconds and
compare with the flask at room temperature. Draw up a table to record your results
OBSERVATIONS AND RESULTS
a. Effect of pressure or volume on equilibrium
b. Effect of temperature on the equilibrium
QUESTIONS
1. What happened to the concentration of the two gases immediately after the volume was
reduced but before the system adjusted to re-establish equilibrium? Explain your
observation.
7
2. Explain what happened to the colour as the system re-established equilibrium. Use the
equation in your answer.
3. If the volume of the gas mixture was increased predict the effect this would have on the
equilibrium and thus on the colour of the mixture.
4. Temperature had an effect on equilibrium. Explain this effect using the equation for the
reaction. Remember it is an exothermic reaction in the forward direction.
8
EXPERIMENT 24
Choose equipment and perform a first-hand investigation to gather information and qualitatively
analyse an equilibrium reaction
INVESTIGATING AN EQUILIBRIUM REACTION
INTRODUCTION
A reversible chemical reaction is one in which both the forward and reverse reactions occur. When
these two reactions are occurring at the same rate there is no change in the macroscopic properties
(e.g. colour) of the system and it is described as being at equilibrium.
A common example of a reversible reaction is the reaction between iron(III) ions and thiocyanate
2+
ions (SCN–) to produce iron(III) thiocyanate ions (FeSCN ) . The equilibrium reaction is given
below:
3+
2+
Fe + SCN–
FeSCN
The iron(III) thiocyanate ions are a blood red colour.
When changes are made to a system in equilibrium the system reacts according to Le Chatelier’s
principle. Changes in the above system can be detected by a corresponding change in colour
intensity.
AIM
To observe the effect of a change in conditions to system at equilibrium and to explain this in terms
of Le Chatelier’s principle.
EQUIPMENT
1 X 50mL beaker
2 x 100mL beakers
Semi micro test tubes and rack
50mL measuring cylinder
Graduated plastic pipettes
Thermometer
Ice
CHEMICALS
0.1M iron (III) nitrate
0.9M sodium hydroxide
0.1M potassium thiocyanate
0.05M silver nitrate
RISK ASSESSMENT
SAFETY: Wear safety glasses. Sodium hydroxide is corrosive so avoid contact with skin. If
contact occurs wash thoroughly with water.
WHAT IS THE
RISK
WHY IT IS THE RISK (Risk to
self and risk to environment)
9
HOW YOU MIGHT MINIMISE
THE RISK
METHOD:
1 Measure 25 mL of distilled water into the 50 mL beaker.
2 Using a clean pipette for each, to the beaker add 1.0 mL of 0.1 mol/L iron(III) nitrate (Fe(NO3)3)
solution and 1.0 mL of 0.1 mol/L potassium thiocyanate (KSCN) solution. Mix thoroughly.
Record your observations.
3 Pipette 2 mL of the mixture into each of seven semi micro test tubes and label them A–G.
4 A is the control. To B add 5 drops of the Fe(NO3)3 solution.
5 To C add 5 drops of the KSCN solution.
6 To D add 5 drops of 0.9 mol/L NaOH solution.
7 To E add 5 drops of silver nitrate.
8 Place F in a beaker of ice
9 Place G in a beaker of water at 80○C
10 Record your observations of the seven beakers. Note any change in colour by comparing each
test tube with the control. To compare colours hold the test tubes over a piece of white paper and
look through them.
RESULTS
CHEMICALS
Iron (III) nitrate (Fe(NO3)3 solution
OBSERVATIONS (COLOUR)
Potassium thiocyanate (KSCN) solution
A
Fe(NO3)3 + KSCN
B
Fe(NO3)3 + KSCN + additional Fe
C
Fe(NO3)3 + KSCN + additional SCN–
D
Fe(NO3)3 + KSCN + NaOH solution
E
Fe(NO3)3 + KSCN + AgNO3
F
Fe(NO3)3 + KSCN in ice bath
G
Fe(NO3)3 + KSCN in water bath at 80○C
3+
In order to help us understand more clearly the changes that are taking place in the chemical system
in this investigation, we can draw diagrams representing the way the concentrations of the reactants
and products change with time.
For example, here is a diagram to represent what happens when the drops of 0.1mol/L iron(III)
nitrate solution were added to the equilibrium mixture.
concentration
in mol/L
Key
concentration of
Fe3+
concentration of
SCNconcentration of
FeSCN2+
time
5 drops of 0.1 mol/L iron(III) nitrate
solution are added at this point
10
When the drops of 0.1mol/L iron(III) nitrate solution are added, the concentration of Fe3+ rises
suddenly. After this the system responds in order to re-establish the equilibrium. It does so by
favouring the forward reaction for a while which uses up some of the excess Fe3+ ions. This also
uses up some of the SCN- ions and increases the concentration of the FeSCN2+ ions as shown on the
diagram. Equilibrium is once again established at the point where the concentrations of the
reactants and the product no longer change.
Complete the following diagrams in a similar way to the above to indicate the effects of
imposed changes
concentration
in mol/L
concentration
in mol/L
time
time
5 drops of 0.9mol/L sodium hydroxide solution
are added at this point
5 drops of 0.1mol/L potassium thiocyanate
solution are added at this point
concentration
in mol/L
concentration
in mol/L
time
time
the equilibrium mixture is cooled at this
point
5 drops of 0.05M silver nitrate solution are
added at this point
concentration
in mol/L
time
the equilibrium mixture is warmed at this
point
11
QUESTIONS
Explain each of the following in terms of Le Chatelier’s principle.
3+
1 What effect did the addition of Fe have on the system?
_____________________________________________________________________________
_____________________________________________________________________________
2 What effect did the addition of SCN– have on the system?
_____________________________________________________________________________
_____________________________________________________________________________
3 What effect did the addition of NaOH solution have on the system?
_____________________________________________________________________________
_____________________________________________________________________________
4 What effect did the addition of AgNO3 have on the system?
_____________________________________________________________________________
DO YOU NEED THESE QUESTIONS AS
WELL? Aim states to explain in terms of Le
Chatelier’s principle
12
EXPERIMENT 25
Perform first-hand investigations to observe the reactions of sulfuric acid acting as an oxidising
agent and a dehydrating agent
INTRODUCTION
Worldwide, more sulfuric acid is produced than any other chemical. It is used in a diverse variety of
industries including the manufacture of fertiliser, detergents, synthetic fibres, pigments and
explosives.
This diversity of uses stems from the variety of chemical reactions sulfuric acid undergoes. It can be
used as an oxidising agent, a catalyst, an electrolyte, a precipitating agent and a dehydrating agent.
In this experiment you will explore the action of sulfuric acid as an oxidising agent and a
dehydrating agent.
AIM
To observe the reactions of sulfuric acid as an oxidising agent and as a dehydrating agent.
EQUIPMENT
Test tubes and rack
100mL beaker
Glass petri dish
CHEMICALS
Conc sulfuric acid
2M sulfuric acid
Zinc
Iron
Sucrose
Wood
Copper sulfate
RISK ASSESSMENT
SAFETY: Concentrated sulfuric acid is highly corrosive. Wear safety glasses, protective clothing
(apron or laboratory coat) and gloves. Avoid contact with skin. If contact occurs wash under cool
running water for at least 15 minutes. Have sodium bicarbonate available to neutralize spills and
clean up spills immediately. Follow instructions for disposal of materials and chemicals
WHAT IS THE
RISK
WHY IT IS THE RISK (Risk to
self and risk to environment)
13
HOW YOU MIGHT MINIMISE
THE RISK
METHOD:
FUME CUPBOARD DEMONSTRATIONS
Part A—Sulfuric acid as an oxidising agent
Perform this reaction in a fume cupboard
1 Clean each of the pieces of metal with steel wool or sandpaper to remove any oxide coating.
2 Add a piece of each metal to a separate test tube.
3 Stand these test tubes in a test tube rack and place them in a fume cupboard.
4 Add 5 mL of concentrated sulfuric acid to each of these test tubes.
5 Record your observations in the results table
Part B—Sulfuric acid as a dehydrating agent
Perform these reactions in a fume cupboard
1 Place 1 g of sugar in a 100 mL beaker. Carefully add 1–2 mL of concentrated sulfuric acid. Do
not handle the material produced.
Feel the outside of the beaker once the reaction is complete. Record your observations.
2 Place a couple of drops of concentrated acid on a paddle pop stick. Record your observations.
3 Place about a gram of copper sulfate pentahydrate in a beaker and add a few drops of
concentrated sulfuric acid. Record your observations
4 In a sealed container a sample of copper sulfate pentahydrate has been set up with a separate
sample of concentrated sulfuric acid and left for several days. Record your observations
STUDENT EXPERIMENTS
1 Add a clean piece of each metal to separate test tubes in a test tube rack and add 5 mL of
2 mol/L sulfuric acid to each. Record your observations in the results table.
2 Place about 1g of sugar in a 100mL beaker and add 1-2 mL of 2M sulfuric acid. Record your
observations
RESULTS
OBSERVATIONS
2 M SULFURIC ACID
CONCENTRATED SULFURIC ACID
Zinc
Iron
Sugar
Wood
Copper
sulfate
Direct:
***
Indirect:
14
CONCLUSION
QUESTIONS
1
Compare the reactivity of concentrated and dilute sulfuric acid.
_____________________________________________________________________
_____________________________________________________________________
2
Write balanced equations for the reactions which occurred between concentrated sulfuric
acid and metals.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
3 a
What gas is produced in the reactions between dilute sulfuric acid and metals?
____________________________________________________________________
b
Write the net ionic equation for any reactions.
____________________________________________________________________
4 Write a balanced equation for the reaction of sugar (C12H22O11) with concentrated sulfuric acid.
_____________________________________________________________________
15
EXPERIMENT 26
Identify, plan and perform a first-hand investigation to identify the products of the electrolysis of an
aqueous solution of sodium chloride
ELECTROLYSIS OF SODIUM CHLORIDE
INTRODUCTION
Electrolytic cells have many applications. In the chemical industry electrolysis is used in the
manufacture of metals such as sodium, magnesium and aluminium, as well as in the production of
chlorine gas and sodium hydroxide. It is also used in electroplating metals.
In this experiment you will electrolyse a concentrated aqueous solution of sodium chloride and a
dilute aqueous solution of sodium chloride, examine the chemistry involved and identify the
products formed at the electrodes.
AIM
To investigate the chemistry involved in electrolysing different aqueous solutions of sodium
chloride.
EQUIPMENT
2 Voltameters
2 20V power packs
Red and blue litmus paper
CHEMICALS
Saturated NaCl
Universal Indicator
0.1M NaCl
RISK ASSESSMENT
SAFETY: Wear safety goggles and protective clothing. Make sure power source is turned off when
connecting and disconnecting electrodes. Chlorine gas is poisonous so work in fume cupboard and
avoid breathing the vapour.
WHAT IS THE
RISK
WHY IT IS THE RISK (Risk to
self and risk to environment)
16
HOW YOU MIGHT MINIMISE
THE RISK
METHOD:
Part A - DEM in FUME CUPBOARD - Electrolysis of saturated sodium chloride solution with
inert electrodes
1. Clamp a voltameter to a retort stand. Fill with saturated NaCl at 55oC.
2. Set the power supply to 20 V and switch on the power. Electrolyse the solution.
3. Observe and record any changes in the results table, such as colour of the solution or
electrode, evolution of a gas or deposition of a solid, at each electrode. Caution: Do not try
to smell any gas being produced.
4. Switch off the power. Remove the gas. To show the presence of chlorine, allow some gas
into a test tube containing wet litmus paper. The litmus paper will be decolourised in the
presence of chlorine
5. To determine the pH of the solution at each electrode introduce the universal indicator into
the hole in the glass tap. You can see the initial colour before it is bleached by the chlorine.
6. Record your observations and pH results in a table.
Part B - DEM - Electrolysis of 0.1 M sodium chloride solution.
1
Repeat steps 1–6 as for Part A using a dilute solution of sodium chloride (0.1M).
RESULTS
Observations (e.g. colour change, gas or solid production, pH)
ANODE
CATHODE
Part A
Electrolysis of
saturated NaCl
solution
Part B
Electrolysis of
dilute NaCl
solution
CONCLUSION
17
QUESTIONS
1. Complete the following table giving all possible electrode reactions.
ELECTRODE REACTIONS
ANODE
CATHODE
Concentrated solution
Dilute solution
2. From the possible electrode reactions for each electrolyte cell use your experimental results to
decide which of the reactions which actually took place.
________________________________________________________________________________
________________________________________________________________________________
3. Write the overall reaction for each cell.
________________________________________________________________________________
________________________________________________________________________________
5.
Suggest possible differences in the solution and electrodes in parts A and B after both solutions
had been electrolysed for 30 minutes. Give reasons for these differences.
18
EXPERIMENT 27
MAKING AN EMULSION
Perform a first-hand investigation to gather information and describe the properties of a named
emulsion and relate these properties to its uses
INTRODUCTION
An emulsion consists of a mixture in which small drops of one liquid are suspended throughout
another liquid. There are two kinds of emulsion involving oil and water. One is a mixture of oil in
water where small droplets of oil are spread throughout the water. Mayonnaise, thickened cream
and moisturisers are examples of this type of emulsion. The other kind of emulsion is a mixture of
water in oil, where tiny drops of water are spread throughout the oil. Butter, margarine, salad
dressings and lipsticks are all examples of water-in-oil emulsions.
The emulsions tend to feel like the main component so a water-in-oil emulsion will usually feel
greasy or oily while oil-in-water emulsions like hand creams and moisturisers will feel ‘lighter’ or
less greasy and will dry on the skin as the water evaporates.
All emulsions need a surfactant to stabilise them. This can be a naturally occurring compound (such
as casein in milk or lecithin from egg yolk in mayonnaise) or can be a synthetic surfactant (such as
those used in cosmetics).
AIM
To prepare an oil-in-water emulsion (mayonnaise) and investigate its properties.
EQUIPMENT
50mL measuring cylinder
25 mL measuring cylinder
A stick mixer
CHEMICALS
40 mL salad oil (e.g. olive oil)
2 egg yolks
50 mL vinegar
METHOD:
Dem
1. Add 40 mL oil and 50mL of vinegar to the mixing container.
2. Mix for approximately 30 seconds. Observe
3. Leave for a short time. Observe.
4. Add 2 egg yolks and process for approximately 2 minutes. Observe
5. Describe the properties (e.g. colour, texture, feel, appearance) of this mixture. Do not taste!
19
RESULTS
Property
Colour
Observation
Texture
Feel
Appearance
CONCLUSION
QUESTIONS
What changes were observed after the oil and vinegar were first mixed?
_____________________________________________________________________
______________________________________________________________________
How long did these changes last?
_____________________________________________________________________
_____________________________________________________________________
What was the emulsifying agent in this experiment?
_____________________________________________________________________
What changes were observed when the oil, vinegar and egg yolks were mixed and how long did they
last?
_____________________________________________________________________
_____________________________________________________________________
20
Compare the properties of the final mixture to those of the individual components.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
6 Consider the following properties of the emulsion—colour, texture (smooth or grainy), feel (oily,
sticky, greasy), appearance, and relate these to the purpose for which this emulsion is used.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
21
EXPERIMENT 28
SAPONIFICATION
Perform a first-hand investigation to carry out saponification
INTRODUCTION
Soap has been in use for a long time and it is thought to have been discovered accidentally around
3000 BC. For centuries it was made from animal fats and lye (NaOH) which was obtained by
pouring water through wood ashes. The processes of manufacturing soap have been refined over
time.
Soap is now made commercially by heating various vegetable oils or animal fats with about 30%
sodium hydroxide. Sodium chloride is added to the mixture to precipitate the sodium salts of the
fatty acids as a thick layer of crude soap, which is purified, coloured and perfumed.
In this experiment you will saponify a vegetable oil. The product will be tested in Expt 28.
AIM
To make soap from a vegetable oil and compare the properties of the product with a commercially
produced soap.
EQUIPMENT
Hotplate
600mL water bath
250 mL beaker (reaction vessel)
100 mL measuring cylinder
10 mL measuring cylinder
Beaker tongs and rubber band
Small sieve
Stirring rod
CHEMICALS
25 mL 3M Sodium hydroxide soln in 50% ethanol/water
8mL rice bran oil
150 mL saturated sodium chloride solution
RISK ASSESSMENT
SAFETY: Wear safety goggles and protective clothing.
WHAT IS THE
RISK
WHY IT IS THE RISK (Risk to
self and risk to environment)
22
HOW YOU MIGHT MINIMISE
THE RISK
METHOD:
Part A—Making soap
1. Set up a water bath by placing a 600 mL beaker half filled with water on hot plate.
2. Pour 8 mL rice bran oil into a 250 mL beaker.
Slowly add 25mL of the NaOH solution to the vegetable oil, stirring continuously during the
addition. (The ethanol does not take part in the reaction but assists the reaction between the oil
and sodium hydroxide.)
3. Using beaker tongs and a rubber band place the beaker containing the reaction mixture in the
water bath and boil gently, stirring frequently.
Caution: if it is overheated the mixture may spit out of the beaker. Keep your face away from
the beaker and make sure it is stirred frequently to prevent spattering.
Wear Goggles at all times
4. After about 30 minutes of heating and stirring the oil should be dissolved and the mixture
should look thick and creamy.
5. Add 25 mL water to the hot solution and stir.
6. Pour this mixture into a 250 mL beaker containing 150 mL saturated sodium chloride solution
and stir. Allow to cool. (This separates the glycerol from the soap)
7. Remove the soap layer and place in a 50 mL beaker.
8. Rinse a couple of times with distilled water to remove excess NaOH.
9. Place the rinsed soap on some paper towel to dry. Keep for Experiment 28.
OBSERVATIONS
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
QUESTIONS
Write the reaction for saponification of a typical oil with sodium hydroxide.
23
EXPERIMENT 29
Perform a first-hand investigation to demonstrate the effect of soap as an emulsifier
SOAP AS AN EMULSIFYING AGENT
INTRODUCTION
A soap molecule has dual properties based on its structure. One end of the molecule is hydrophobic
and is therefore attracted to non-polar substances like grease and oil while the other end is
hydrophilic and is attracted to polar substances such as water. Soap is able to create an emulsion by
attaching to both grease and water.
When soap is added to a greasy substance the hydrophobic end is embedded in the grease. When
this substance is then washed in water the hydrophilic ends are attracted to the water and eventually
the greasy material is rinsed away.
AIM
Aim: To investigate the effectiveness of soap as an emulsifier.
EQUIPMENT
4 x 50 mL beakers
10 x test tubes with stoppers
Measuring cylinder or graduated dropper
CHEMICALS
Hard water
Your own soap
Soap flakes shaved from a bar of laundry or bath soap
5 mL liquid hand wash
5 mL washing-up detergent
5 mL cooking oil
Distilled water
0.1M HCl
Universal indicator
RISK ASSESSMENT
SAFETY: Wear safety glasses, as soap can sting if it gets in the eyes
METHOD:
1. Make a soap solution by half filling a 50 mL beaker with distilled water, then add some soap
flakes (approx. ½ tsp), stirring until they are dissolved.
2. Make up similar solutions using the liquid hand wash, detergent and your own soap
Part A – Comparing different emulsifying agents
3. Place 2mL of each solution in separate test tubes and determine the pH of each solution with
universal indicator
4. Place 5mL of each solution in separate test tubes, stopper and shake vigorously. Measure the
amount of lather produced
24
Part B - Comparing the effect of different emulsifying agents on other substances
5. In one test tube place 10 mL distilled water and 2 mL of oil. Stopper and shake well to mix.
Record your observations immediately after shaking. Place the test tube in a test tube rack and
record your observations once the mixture has settled. ( Note this sample has no emulsifying
agent and can be used as a comparison)
6. Add 2mL of oil to each of four test tubes. Then add 10 mL of the soap solution to one of the test
tubes, 10 mL of the liquid hand wash solution to the second, 10 mL of detergent solution to the
third test tube and 10mL of your soap solution to the fourth. Stopper each test tube and shake
vigorously. Record your observations.
7. Add 5 mL 0.1M HCl to each of four fresh test tubes. Then add 5 mL of the soap solution to one
of the test tubes, 5 mL of the liquid hand wash solution to the second, 5 mL of detergent
solution to the third test tube and 5mL of your soap solution to the fourth. Stopper each test tube
and shake vigorously Record your observations.
8. Add 2mL of oil to each of the test tubes from step 7. Stopper and shake vigorously. Record your
observations.
9. Repeat steps 7 and 8 using the hard water instead of 0.1M HCl. Record your observations.
RESULTS
Test tube with oil and water only (observations)
________________________________________________________________________
________________________________________________________________________
Part A – Comparing different emulsifying agents
SOAP FLAKE
LIQUID HAND
DETERGENT
YOUR SOAP
SOLUTION
WASH
SOLUTION
SOLUTION
SOLUTION
pH
Height of lather
produced on
shaking
25
Part B - Comparing the effect of different emulsifying agents on other substances
SUBSTANCE
SOAP FLAKE
LIQUID HAND
DETERGENT
YOUR SOAP
ADDED
SOLUTION
WASH
SOLUTION
SOLUTION
SOLUTION
Oil
0.1M HCL
0.1M HCl and oil
Hard water
Hard water and oil
CONCLUSION
QUESTIONS
1 Compare the appearance of the oil and water mixture with the oil and soap solution mixture. Did
soap act as an emulsifier?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2 Did acid affect the action of soap or detergent as an emulsifier? How could you tell?
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
26
3 What effect, if any, did the hard water have on the actions of soap and detergent?
_____________________________________________________________________
______________________________________________________________________
_____________________________________________________________________
4 Explain why detergents are more commonly used than soaps.
______________________________________________________________________
______________________________________________________________________
27
EXPERIMENT 30
Perform a first-hand investigation to assess risk factors and then carry out a chemical step involved
in the Solvay process, identifying any difficulties associated with the laboratory modelling of the
step
MODELLING THE SOLVAY PROCESS
INTRODUCTION
Perform a first-hand investigation to assess risk factors and then carry out a chemical step involved
in the Solvay process, identifying any difficulties associated with the laboratory modelling of the
step
Sodium carbonate is a very useful chemical. It is used as an intermediate in the production of other
chemicals and in the manufacture of glass, detergents and soaps, metals and mining, paper and
textiles. Synthetic sodium carbonate is produced in South Australia at Penrice Soda Products using
the Solvay process.
AIM
To model steps in the Solvay process and compare the laboratory modelling with the industrial
process.
EQUIPMENT
Gas generator
Filter funnel and stand
Filter paper
150 mL conical flask
1 large test tube
20 mL measuring cylinder
2 x 100 mL beakers
CHEMICALS
10 g NaCl
10 mL 0.1 mol/L Na2CO3 solution
1 g MgCl2
5 mL 1.0 mol/L NaOH solution
0.5 g CaCl2
5 g NaHCO3
20 mL ammonia/ammonium chloride solution (10g ammonium chloride dissolved in 20mL 25%
ammonia)
30 mL limewater (saturated Ca(OH)2 solution)
Red litmus paper
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RISK ASSESSMENT
Safety: Wear glasses and protective clothing. Check the material safety data sheet for ammonia.
Carry out hydrogen carbonate formation and ammonia recovery steps in a fume cupboard.
WHAT IS THE
RISK
WHY IT IS THE RISK (Risk to
self and risk to environment)
HOW YOU MIGHT MINIMISE
THE RISK
METHOD:
Step A Brine purification
1. To make a seawater solution, measure 20 mL distilled water into a 100 mL beaker. Add
7 g NaCl, 0.8 g MgCl2 and 0.2 g CaCl2 to the distilled water, stir well to ensure all salts are
dissolved.
2+
2. Add 2 mL 0.1 mol/L Na2CO3 to precipitate the Ca ions.
2+
3. Add 1 mL 0.9 mol/L NaOH solution to precipitate the Mg ions.
4. The solution should now be filtered to remove the precipitates and the solid residue discarded.
Step B DEM - Hydrogen carbonate formation
1. Add 20 mL of ammonia solution to a prepared brine filtrate (similar to that from Step A) and stir.
2. Pour the solution into a conical flask ensuring any solid remains in the beaker.
3. Bubble carbon dioxide through the solution from a gas generator or gas cylinder. (Carbon dioxide
is readily generated by dripping hydrochloric acid onto marble chips in a gas generator.)
4. Allow the CO2 to bubble through the mixture for approximately 10 minutes. A white precipitate
of sodium hydrogen carbonate should form.
5. Try to separate the precipitate by filtering the solution.
6. If filtering did not work allow the precipitate to settle and decant the liquid into a clean
100 mL beaker.
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Step C Sodium carbonate formation
1.
Place 2 g NaHCO3 in a large test tube and fit with a gas delivery tube and stopper.
Clamp the test tube in a stand as shown in the diagram below.
2. Half fill another test tube with limewater and place the gas delivery tube in it.
3. Heat the NaHCO3 strongly to convert it to Na2CO3. Record your observations. Caution: remove
the limewater tube before removing the Bunsen burner.
Step D DEM Ammonia recovery
1. Transfer 5 mL of the filtrate from Step B into a clean test tube.
2. Add 5 mL limewater and heat gently. Hold moist red litmus paper near the mouth of the test tube
to check for the presence of ammonia. Record your observations.
CONCLUSION
QUESTIONS
1
2+
2+
Why do the Ca and Mg ions need to be removed from the brine solution?
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2
How are the precipitates removed in the industrial process?
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3
In the Solvay process CO2 is obtained by heating limestone in a kiln. Why could this
not be done in the school laboratory?
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In industry the temperature of Solvay tower (carbonator) is carefully controlled to
give sodium bicarbonate crystals of the required size to facilitate filtration. Compare
this with the school laboratory filtration in Step B.
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4
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What other products are present in the reaction in Step B? How are these removed in
the industrial process?
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5
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6
Write the chemical equation for the reaction occurring in Step D.
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