EXPERIMENT 4 : Preparation of Double Salt and Complex Salt EXPERIMENT 4 : Preparation of Double Salt and Complex Salt
OBJECTIVES: OBJECTIVES: 1.
1. Prepare complex Prepare complex and double and double saltsalt
2. Differentiate between complex and double salt 2. Differentiate between complex and double salt
3. Identify the bond character between complex and double salt 3. Identify the bond character between complex and double salt
THEORY THEORY
In this experiment, we are preparing different salt that is double salt and complex In this experiment, we are preparing different salt that is double salt and complex salt. For the first one,
salt. For the first one, double saltdouble salts s contaicontaining more than ning more than one cation or one cation or anion. They formanion. They form when one salt and more dissolved in a liquid then together crystallize in a regular pattern. when one salt and more dissolved in a liquid then together crystallize in a regular pattern. They have their own crystal forms which need not be the same as that of either of their They have their own crystal forms which need not be the same as that of either of their com
componponenent t sasaltlts. s. ThThis is is is a a sosolilid d ststatate e phephemnmnomomenenon on whewhere re in in sosolulutition on ththey ey araree decomposed completely, or nearly so, into of their component salts. In this respect double decomposed completely, or nearly so, into of their component salts. In this respect double salt are distinguished from complex salts, which give complex ions of their own in salt are distinguished from complex salts, which give complex ions of their own in solution. Double salts are extremely numerous.
solution. Double salts are extremely numerous.
Complex salt is another type of salt. It is a salt that does not dissociate in solution. Complex salt is another type of salt. It is a salt that does not dissociate in solution. When ammonia is added to a solution of a cupric salt, a light blue precipitate of cupric When ammonia is added to a solution of a cupric salt, a light blue precipitate of cupric hydroxide is first formed which dissolves in excess of ammonia to form a deep hydroxide is first formed which dissolves in excess of ammonia to form a deep purplish- blue soluti
blue solution. The on. The colour is due to colour is due to the complex ion Cu(NHthe complex ion Cu(NH33))44++. The sulfate of this ion is. The sulfate of this ion is
easily obtained in solid form as the hydrate Cu(NH
METHODOOGY
Double salt, CuSO4.(NH4)2SO4.6H2O
0.03mole of copper sulfate + 0.03mole ammonium sulfate was added into a beaker contain 15ml of hot water
↓ Coll filter ↓ Dry, weight ↓ Observe
Complex salt, Cu(NH3)4SO4.H2O.
10ml [NH3] + 6ml H2O and 6.25g copper sulfate was put into a beaker
↓
10ml ethyl alcohol was added ↓ 1 hour ↓ Cool ↓ Filter ↓
↓
Wash with 10ml ether ↓
Dry in oven ↓ weight
RESULT AND CALCULATION
A) Double salt
Sample Number of mole
(mole) Mass of theory (g) Mass used in experiment (g) CuSO4.5H2O 0.03 7.49 7.49 (NH4)2.SO4 0.03 3.96 3.69
Mass of filter paper 1.12 g
Mass of filter paper + sample 7.89 g
Mass of sample 6.74 g
Calculation
Salt CuSO4.5H2O
No. of mole = 0.03 mole
Mass of relative molecule = [(63.546) + (32.066) + 9 (16) + 10 (1.0079)]
= 249.691
Mass = (0.03) (249.691)
Salt (NH4)2.SO4
No. of mole = 0.03 mole
Mass of relative molecule = [2 (14.007) + 8 (1.0079) + 32.066 + 4 (15.999)]
= 132.13292
Mass =3.96 g
Reaction equation:
CuSO4.5H2O + (NH4)2.SO4+ H2O → CuSO4.(NH4)2SO4.6H2O
The mass of sample of CuSO4.(NH4)2SO4.6H2O from this experiment
= 6.74 g
From the theory, mass of CuSO4.(NH4)2SO4.6H2O
Mass = no. of mole x mass of relative molecule
Mass of relative molecule : (63.546) + 2 (32.066) + 14 (15.999) + 20 (1.0079) + 2 (14.007)
= 399.836 g/mole
Mass in theory : (0.08) (399.836)
= 11.005 g
% of sample from experiment
Mass in theory = 6.47 g x 100 11.005 g = 61.24 % % of error = (11.005 g – 6.74 g) x 100 11.005 g = 38.76 %
B) Complex salt, Tetrammine Cupric Sulfate CuSO4.(NH4)2SO4.6H2O
Sample Mass of theory
(g) Mass used in experiment (g) Volume (ml) CuSO4.5H2O 6.24205 6.25 - NH3 - - 10
Mass of filter paper 1.13 g
Mass of filter paper + sample 5.13 g
Mass of sample 4.00 g
Calculation : Salt CuSO4.5H2O
No. of mole : 0.025 mole
Mass of relative molecular : [(63.546) + (32.066) + 9 (15.999) + 10 (1.0079)] = 249.682 g/mole
Mass : (0.025) (249.682)
= 6.24205 g
The equation of reaction :
CuSO4.5H2O + 4NH3 → Cu(NH3)4SO4.H2O + 4H2O
From theory, mass of Cu(NH3)4SO4.H2O
= no. of mole x mass of relative molecule
Mass of relative molecule = 63.546 + 4 (14.007) + 32.066 + 5 (15.999) + 14 (1.0079)
= 245.7456 g/mole
Mass from theory = 0.025 x 245.7456
= 6.14364 g
% of sample from experiment
= mass from experiment x 100
Mass from theory
= 4.00 x 100 6.14364 = 65.108 % % errors : (6.14364 - 4.00) x 100 6.14364 = 34.892 % Observation :
Observation Double salt Complex salt
Homogeneous Homogeneous Heterogeneous
Appearances
- colour, crystal size
Sky blue
Diamond shape
Deep blue Rod shape
Behaviour in solution Dissolve Cannot dissolve
DISCUSSION
Preparation of CuSO4.(NH4)2SO4.6H2O and Cu(NH3)4SO4.H2O show the difference in
From the experiment, we found out that double salt can dissolve in water. Double salt
produce a homogeneous solution. The appearance are diamond shape. Formation of Cu2+
make the solution colour are sky blue.
From the experiment, double salt is CuSO4.(NH4)2SO4.6H2O. The formation of crystal is
observed in sky blue colour and has a shining and coarse surface. Do not stir during the cooling process to get the right result. The salt is highly soluble to form homogeneous solution. 6.74 g salt mass formed while the theory value is 9.9959 g. The percentage error is 38.76%
Equation reaction:
CuSO4.5H2O + (NH4)2SO4 → CuSO4.(NH4)2SO4.6H2O
The mass of double salt that we get is very little compare to the theory value. This might be happen because of not all the crystal is fully transferred into the filter paper by using
Buchner funnel. There might have many errors occur in the electrical balance that make the reading not precise. The filtering process is not perfect and caused some crystal lose.
The complex salt is Cu(NH3)4SO4.H2O. The colour of the crystal formed is deep blue.
The structure are weak and not shining. Complex salt cannot dissolve in water. The formation of Cu(NH4)44+ turn the solution into deep blue colour. It is more concentrated
and easy to formed Cu(NH4)4+4 complex ion by leaving the solution for 1 hour. To get
the best result the solution must be cooling in natural. The shape of crystal is small and tiny like rod. Mass of complex salt is 4.00g while the theory is 6.14364g. the percentage error is 34.892%
The reaction is :
The result that we get from experiment and theory are different due to some errors which are, the cooling process is not complete, the error in the electrical balance during take the weight value, some salt is still leaving on the glass when prepare the salt, the crystal lost from the imperfect filtering process and only some the crystal is transfer into the filtering paper by using Buchner funnel.
PRECAUTION
1. Weight CuSO4.5H2O and (NH4)2.SO4approximately.
2. Do the mixture in fume cupboard.
3. Do the cooling process slowly and complete.
CONCLUSION
1. From this experiment we got the mass of double salt is 6.47 g while mass of complex salt is 4.00g.
2. The double salt characteristics are homogenus, dissolve and its appearance is sky blue and diamond shape.
3. The complex salt characteristics are heterogenus, cannot dissolve and its appearance is deep blue and rod shape.
REFERENCES :
1. Shriver & Atkins , Oxford Inorganic chemistry, fourth edition 2. www.tutornext.com/difference-between-double-salt-complex/2461
3. www.britannica.com/eb/topic-129980/complex-ion
QUESTIONS
• Potassium sodium tartrate-in the process of silvering mirror, an ingredient of Fehling’s solution.
• Calcium double salt - additive in food product (such as French Fries and potato chips)
• Alum - purify water and harden plaster of Paris.
2. Metallic cations form complex ions with ammonia.
• Cadmium,
• nickel
• argentum.
3. When the complex salt is dissolved in water, a slight precipitate appears. What is this precipitate, and why is it formed?
Cu(OH)2, because Cu is bind to water molecule.
4. What is the difference in constitution between tetrammine cupric sulfate and cupric ammonium sulfate?
