FACULTY OF APPLIED SCIENCES
NAME STUDENT ID COURSE CODE TITLE OF THE EXPERIMENT LECTURE’S NAME LAB PARTNER’S NAME
BALKIS BINTI HAZMI 2014636182 CHM475 DR. AMALINA MOHD TAJUDDIN NUR ATIQAH AISYAH
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Table of contents PAGE 7. 1
INTRODUCTION
3
7.2
AIMS
3
7.3
APPARATUS AND MATERIALS
3
7.4
METHODOLOGY/PROCEDURE
3-4
7.5
RESULTS
5-16
7.6
DISCUSSION
17-19
7.7
CONCLUSIONS
19
7.8
REFERENCE
19
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Introduction Identifying the properties of a compound is a part of qualitative chemistry. Different compound have different properties in terms of reaction with solvent .To determine the physical properties of the compound, systematic test need to form on that substance . To look the solubility of the compound, precipitate test to see the reaction between two dissolve compound .To determine the acidity and basicity of substances the pH test is done. The color produce during burning test is nearly the same with crystal color. Both of crystals are soluble in water, but to determine the type of the isomer for these compounds are a bit difficult. The addition of excess hydrochloric acid followed by ammonia solution can detect the isomerism. The soluble crystal after being added the hydrochloric acid and ammonia solution is cis-form meanwhile the insoluble is trans-form.
Objective To determine the physical properties and isomer shape of copper (II) and chromium (III) complexes.
Apparatus and material s Test tubes, test tube rack, dropper ,beaker, blue litmus paper, pH meter, copper(II) complex crystal, potassium tris(oxalato) chromium (III)trihydrate, distilled water, measuring cylinder, 5% hydrochloric acid, 5% NaHCO₃, 5% NaOH,,5 M HCl, 5 M ammonia solution, 0.1 M potassium ferrocyanide ,K₄Fe(CN)₆ ,6M CH3COOH ,2 M Pb(CH3COO)2, Bunsen burner, flame wire ,12 M HCl
Procedure The first properties of the crystals that can be seen are the color and shape. The color and shape of the both crystals are recorded into Table 7.1.For solubility and color changes for these crystals,4 clean test tubes are used by adding each of them with 1ml of distilled water, 5% of aqueous HCl, 5% of aqueous NaHCO3, and 5 % of aqueous NaOH .Small amount of the crystals are added into the test tubes and mixed well .The changes of the crystals is observed and then they are put into water bath for 10 minutes to look for the changes in color and solubility .Next test is isomerism to detect weather the structural formula of these crystals 3
are cis-form of trans-form .The crystals are placed on the filter paper resting on the watch glass .The crystals are moisten with few drops of dilute ammonia solution and followed by dilute hydrochloric acid. The dissolve crystal after addition of the dilute ammonia solution and dilute hydrochloric acid is cis-form and the remaining crystal after the reaction is in transform structure of isomerism. Besides, the confirmatory test for the copper and chromium is done to make sure the element is present in the crystal. For confirmatory test of copper, small amount of copper complexes is dissolved with 5 ml of distilled water. 2 ml of it is used and the blue color is faded and the blue litmus paper turned to red after the addition of 6M of HCl.2-3 drops of 0.1 M potassium ferrocyanide K4Fe(CN)6 is added and the brick-red precipitate is formed indicates the present of copper. The chemical equation can be showed as below: (
)
(
)
(
)
(
) ( )
For confirmatory test of chromium, a small amaout chromium crystal is dissolve in 5 ml of distilled water and 2 ml of it is used. A few drops of 6 M CH3COOH, acetic acid is added into the solution until it is acidic then, 5 drops of 2 M Pb(CH3COO)2 lead acetate are added. The yellow color of precipitate will form to indicate to present of chromium (III). The excess solution is used to test the pH reading .The pH paper showed copper have darker color than the chromium (iii). Copper is more basic than chromium (III). In flame test, a wire which been wrap with crystal is tested. Firstly ,the wire is dip into the 12M HCl to make sure it is cleaned .Then ,the wrap wire is burned on the flame until the flame turn into its color .The color of flame is recorded .
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Result Test
Copper complex
Color and shape
Blue
Solubility and color change
Before heating
Black-green After heating
Partially a. Water
dissolve and blue color remain unchanged
b. HCl
Chromium complex Before heating
After heating
The is formation
The chromium
All the crystal is
of blue and
complex crystal
dissolved and the
white ppt. The
dissolved in
dark green color
solution is in
black green
remain unchanged
blue color.
color
Partially
The formation
The chromium
All the crystal is
dissolved (blue
of white ppt.is
complex crystal
dissolved and the
ppt.is formed)
occurred and the
dissolved in
dark green color
and color of
solution color is
black green
remain unchanged
solution turned
faded.
color
to cloudy blue The blue crystal c. NaHCO₃
The crystal is
The chromium
All the crystal is
dissolved and
slightly
complex crystal
dissolved and the
solution turn
dissolved and
dissolved in
dark green color
there is
black green
remain unchanged
precipitate .the
color
solution is blue in color . d. NaOH
The solution
Partially
The chromium
The chromium
turns colorless
dissolve an blue
complex crystal
complex solution
and the blue
color turned to
dissolved in
turned to colorless
black ppt.is
turquoise
black green
and the black ppt.
formed Isomerism Confirmatory test Solution pH
color
is formed.
Cis-form
Trans-form
+ve test brick-red precipitate is
-ve test the white precipitate is
formed ,copper is present
formed no chromium in the crystal
pH 6
pH 2 5
Flame test
Green flame
Purple flame
Photograph 7.1(a) before heating process
Photograph 7.1(b) after heating process 6
Photograph 6.1(a) and 6.1(b) shows the reaction between crystal complexes solution and water
Photograph 7.2(a) before heating process
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Photograph 7.2(b) after heating process Photograph 6.2(a) and 6.2(b) shows the color changed and its solubility after the reaction between complexes solution and hydrochloric acid
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Photograph 7.3(a) before heating process
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Photograph 7.3 (b) after heating process Both photograph 6.3(a) and 6.3(b) shows the color changes and precipitation of complexes crystal solution and NaHCO3 solution
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Photograph 7.4(a) before heating process
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Photograph 7.4(b) after heating process Photograph 6.4(a) and 6.4(b) shows the changes of the complexes crystal solution after the addition of sodium hydroxide NaOH.
Photograph7.5(a)
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Photograph 7.5(b) Photograph 6.5(a) and 6.5(b) shows the condition of the crystals before and after being added with diluted ammonia solution and dilute hydrochloric acid
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Photograph 7.6 the confirmatory test to detect the present of metal ion in the crystal complexes solution.
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` Photograph 7.7 shows the color of flame for copper (ii) oxalate complex crystal
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Photograph 7.8 shows the purple flame o chromium complex crystal after being burn on the flame.
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Discussion A) Copper (II) complexes crystal The copper (II) oxalate complexes crystal is blue in color .The blue color is from the Cu2+ ions. To test the solubility of copper (II) oxalate complex crystal, four types of solvents like water, hydrochloric acid (HCl), sodium hydroxide (NaOH) and NaHCO3 solution are used. The addition of water to the copper (II) oxalate complexes solution gave the result as showed in photograph 6.1(a) and 6.1(b).There is formation of white and blue precipitate and also the whole solution turned to cloudy blue color. The original geometry of K2[Cu(C2O4)2.(H2O)2] is bent shape and after the addition of water the geometry changed to square planar because the water molecules are attached to the copper ion (central metal ion).The other reason of this insolubility is because of the geometry shape, square planar and it is too stable to be dissolved. The white precipitate is formed as the hydrochloric acid, HCl is being added to the copper (II) oxalate complex solution. The precipitate indicates, there is reaction between both solution the formation of insoluble (CuCl4)2+ ion. The blue color of complex solution turned cloudy and faded. The solution of copper (II) complex between the NaHCO3 solution will change the color into blue ocean color and it is partially soluble solution. There is also the formation insoluble salt of CuHCO3. The changes of blue solution into turquoise solution happened after the copper (II) oxalate complex is added with NaOH solution .The turquoise solution is actually partially dissolve solution and it is an intermediate formation of copper (II) hydroxide, Cu(OH)2 .The further reaction between NaOH and Cu(C2O4)2+ will lead to the formation of complex ion [Cu(OH)4]2-. To determine the structural formula of copper (II) oxalate complex crystal molecule, the additions of dilute ammonia solution followed with dilute hydrochloric acid are needed. After the addition of these solution, the blue crystal still remain in solid condition and not dissolved. This reaction confirmed that the blue crystal is in trans-formed of isomer. The trans-structural molecule is hard to dissolve because it is stable enough. The copper (II) oxalate complex is considered as basic form (pH 6) after pH meter is dip into the solution. The present of copper as the central metal ion is confirmed by adding the 17
K4Fe(CN)6 and it gave us the brick-red precipitate at the bottom of test tube as shown in photograph 7.6 . From that test, it is confirmed that the copper ion is presented in the crystal. The reaction can be proved by the chemical equation below: (
)
(
)
(
)
(
) ( )
The flame test for copper (II) oxalate complex produced green flame. The green flame produced indicates the copper (II) ion, Cu2+. When burning, the energy of the crystal is used to excite and the ion backed into their low energy level.
B) Potassium tris(oxalato)chromium (III) trihydrate Chromium is placed under transition element and it have various number of oxidation .The chromium can be Cr2+, Cr3+ and etc. The potassium tris(oxalato)chromium(III) Trihydrate is greenish-black in color. Soluble greenish-black color of crystal solution as the distilled water being added to the crystal. There is also a soluble greenish black solution when the hydrochloric acid added into chromium crystal. The formation of [Cr(C2O4)3Cl]3+ happened after the Cl- ion chemically react with the [Cr(C2O4)3]3+ ion. The formation of [Cr(C2O4)3Cl]3+ ion is temporary and the Cl- will disappear if the solution left over a week. The crystal also dissolved in NaHCO3 solution and produce dark green solution of (Na)3[Cr(C2O4)3]. But there is formation of black precipitate as the NaOH solution added to the greenish-black solution .The precipitate is known as [Cr(C2O4)3OH]3+ as the OH- bind with Chromium(III) oxalate complex ion. The structural shape of the crystal is cis-formed. This structure can be proved after the dilute ammonia solution and dilute hydrochloric acid is dropped the crystal is dissolved as shown in photograph 7.5 (b). To confirm the present of chromium ion as the central metal ion ,the crystal solution is added with the acetic acid and lead(II) acetate .The formation of yellow precipitate should happen but it there is only cloudy precipitate formed at the bottom of test tube as shown in photograph 7.6. This mean there is no chromium present in the crystal because the chromium ion is in small amount. The flame test for the chromium (III) oxalate complex is in purple flame.
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To obtain the accurate result, make sure the test tubes are cleaned from the waste product and to avoid the chemical reaction is slowed down. The purpose of heating process toward the solubility test is to make sure the complete reaction of the chemicals solution and the crystals. The gloves must be ware because of handling strong acid such as 12 M of hydrochloric acid.
Conclusion The physicals properties of both crystals are determined. The copper(II) oxalate complex crystal is insoluble meanwhile most of the chromium(III) oxalate complex crystal is soluble in all the chemical solution accept in NaOH. The blue crystal is trans-formed of isomer meanwhile the chromium, greenish-black crystal is cis-formed structure. The copper is more basic than chromium crystal. The flame of copper is green and chromium is purple color .
References Silberberg, M. (2015) .The Molecular Nature of Matter and Change (7thed) . New York :McGraw Hill Kotz, J C.Treichel,P, M &Weaver,G.C. (2006).Chemistry and Chemical Reactivity (6th ed) ., Canada : Thomson Learning Inc . Miessler,L. Fischer, J.& Tarr, A .(2014). Inorganic Chemistry (5th ed) ., USA :Pearson
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