Leeming SHS – Yr 11 Chem
Student’s Name:
Date:
Preparation of copper(II) sulfate from copper(II) nitrate
Background
The purpose of this laboratory activity is to prepare copper(II) sulfate from
copper(II) nitrate.
This is done by using the following steps:
1.
Precipitation of copper (II) hydroxide Cu(OH)2 from copper (II) nitrate Cu(NO3)2
solution by the addition of NaOH solution.
2.
Conversion of copper (II) hydroxide Cu(OH)2 to copper(II) oxide CuO by
heating.
3.
Neutralisation of copper (II) oxide CuO with sulfuric acid to form copper (II)
sulfate CuSO4.
4.
Evaporation of copper (II) sulfate CuSO4 (l) solution to form solid copper (II)
sulfate CuSO4 (s).
Equipment and Chemicals
analytical balance
beaker 250 mL (x 2) sodium hydroxide [NaOH]
solution
2 mol L-1 (40 mL)
hot plate and magnetic R.O. water in wash
sulfuric acid [H2SO4]
stirrer
bottle
2 mol L-1 (30 mL)
stirrer bar
one boiling chip
spatula
dry filter paper on
watch glass
copper (II) nitrate trihydrate
[Cu(NO3)2.3H2O] (5g)
Safety
sodium hydroxide - http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0360.htm
sulfuric acid - http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0362.htm
copper (II) sulfate - http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc14/icsc1416.htm
H2SO4 NaOH
copper2sulfate.doc
Adapted from STAWA Exp 28
harmful – CuSO4.5H2O
CuSO4
Page 1
Leeming SHS – Yr 11 Chem
Method
Part A – Precipitation of copper(II) hydroxide Cu(OH)2 from copper(II) nitrate
Cu(NO3)2 solution
1.
Weigh out approximately 4.8 g of Cu(NO3)2.3H2O into a TARED 250 mL
beaker on the analytical balance.
2.
Record the exact mass used:
3.
Dissolve the copper (II) nitrate pentahydrate - Cu(NO3)2.3H2O in about 20 mL
of R.O. water.
4.
Put the beaker on a magnetic stirrer and add a stirrer bar carefully to the
solution.
5.
Turn the stirrer on SLOW speed.
6.
Slowly add 30 mL of 2 mol L-1 sodium hydroxide - NaOH solution.
7.
Describe what you see happening in the beaker as you add the NaOH:
Part B - Conversion of copper(II) hydroxide Cu(OH)2 to copper(II) oxide CuO
1.
Add 100 mL of R.O. water to the copper hydroxide - Cu(OH)2 precipitate
the beaker.
2.
Keep the stirrer ON
3.
Turn the heat on LOW and keep heating until the solution turns FROM LIGHT
BLUE colour to BLACK. This is the colour of copper (II) oxide - CuO.
4.
Turn OFF the hot plate and let the beaker cool down.
5.
Without losing any of the SOLID, slowly DECANT as much of the liquid as
possible from the beaker into another 250 mL beaker (labelled WASTE
beaker).
6.
To the first beaker (the one with the black solid in it), add about 100 mL of
R.O. water.
copper2sulfate.doc
Adapted from STAWA Exp 28
Page 2
Leeming SHS – Yr 11 Chem
7.
Use the magnetic stirrer to stir the SUSPENSION for one minute.
8.
When the solid has settled to the bottom, DECANT the liquid into the WASTE
beaker.
Part C - Neutralisation of copper(II) oxide CuO with sulfuric acid to form
copper(II) sulfate CuSO4.
1.
Put the beaker with the black solid suspension on the magnetic stirrer and
set the stirrer to a SLOW stirring speed.
2.
Slowly (and carefully) dropwise add about 20 mL of sulfuric acid - H2SO4 to
the suspension of CuO.
3.
Look carefully to see if any of the black solid is still in the beaker. If there is,
add more drops of sulfuric acid – H2SO4.
4.
Use a magnetic rod to remove the stirrer bar.
5.
Describe what you observed inside the beaker as the acid was added:
Part D - Evaporation of copper(II) sulfate CuSO4 (l) solution to form solid
copper(II) sulfate CuSO4 (s).
1.
Add a boiling chip (anti-bumping granule) to the solution and heat the
solution on the hot plate until the volume is reduced to about 10 mL.
Use the markings on the side of the beaker as a guide to the volume.
2.
Turn OFF the heat and take out the boiling chip. Use a clean spatula to do
this.
3.
Crystals of copper (II) sulfate should start to form as the solution cools down.
If there is not enough time to precipitate out the crystals, put a label on the
beaker with your name, date and compound’s name/formula.
Put the beaker in an approved storage cupboard until the next lesson. See
the lecturer for a safe place to store the solution.
copper2sulfate.doc
Adapted from STAWA Exp 28
Page 3
Leeming SHS – Yr 11 Chem
Part E – Weighing the copper(II) sulfate crystals
1.
Transfer the copper (II) sulfate pentahydrate crystals – CuSO4.5H2O to a
pre-weighed or TARED filter paper or weighing bottle.
Record the mass of crystals in the space:
Post Lab Assignment
1. Write equations to represent the four steps in the preparation of CuSO4.5H2O.
Step 1
Word Equation
Symbolic Equation
Step 2
Word Equation
Symbolic Equation
Step 3
Word Equation
Symbolic Equation
Step 4
Word Equation
Symbolic Equation
copper2sulfate.doc
Adapted from STAWA Exp 28
Page 4
Leeming SHS – Yr 11 Chem
2.
Use the starting mass of Cu(NO3)2.3H2O and the equations from Question 1.
to calculate the theoretical amount of copper sulfate that you should have
made.
Show each step of your calculation in the space below:
Step 1
Step 2
Step 3
Step 4
3.
Calculate the percentage yield of copper(II) sulfate pentahydrate based on
the amount of copper(II) sulfate pentahydrate that you made and the
theoretical amount that you calculated in Question 2.
% yield CuSO4 .5H 2 O =
copper2sulfate.doc
mass of CuSO4 .5H 2 O produced
mass of CuSO4 .5H 2 O theoretical
Adapted from STAWA Exp 28
x 100
Page 5
Leeming SHS – Yr 11 Chem
5.
a)
Was your percentage yield for CuSO4.5H2O = 100% ?
b)
Briefly describe what events could have occurred during the
preparation to give you a result other than 100% yield.
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•
•
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6.
What could you do next time to improve your percentage yield of
CuSO4.5H2O?
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copper2sulfate.doc
Adapted from STAWA Exp 28
Page 6