Report for Lab. 5
Name_______________________
Section: CHM1033 Lab. Wednesday 9 am course 1941
Date: October 2021
Precipitations tests
• Use only clean test tubes. Rinse each with deionized water.
• Do not put any tool into the test tube which has not been rinsed with
deionized water.
• Precipitation tests:
• Some compounds are insoluble in water. When ions react in solution to
produce insoluble compounds a solid called precipitate (ppt) come in many
colors but most of them are white. You can tell when you have a ppt
because the solution will become cloudy or opaque.
• You need 2 test tubes for each ion to be tested. In one test tube you will
add the ion to be tested and in the second test tube you will use deionized
water to observe a negative test.
Calcium test and Chloride test.
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1. Place 10 drops of Ca Cl2 solution to test tube 1.
2.Place 10 drops of deionized water in test tube 2.
3.Add 20 drops (1 mL)of 1% Na2CO3 solution to each of them and mix.
4.- Describe and record the results.
Chloride test:
1. Place 10 drops of 1% Na Cl solution to test tube 1.
2.Place 10 drops of deionized water in test tube 2.
3.Add 20 drops (1 mL)of 0.1M AgNO3 solution to each of them and mix.
4.- Describe and record the results.
Disposal: all the solutions must be disposed on the heavy metal waste
container, under the hood. NOT DOWN THE DRAIN.
Complexation tests
• Test for Fe+3
• 1. Place 10 drops of 1%Fe(NO3)3 solution to test tube 1.
• 2.Place 10 drops of deionized water in test tube 2.
• 3.Add 10 drops (1 mL)of 1% KSCN solution to each of them and mix.
• 4.- Describe and record the results.
• Test for Cu+2
• 1. Place 10 drops of 1% Cu(NO3)2 solution to test tube 1.
• 2.Place 10 drops of deionized water in test tube 2.
• 3.Add 20 drops (1 mL)of 1M NH4OH solution to each of them and mix.
• Caution—ODOR HAZARD
4.- Describe and record the results.
Disposal: The content of each test tube may be poured down the drain
with running water
Part 1. Testing for specific ions.
Describe the visible changes which occurred in each test tube
Ion
Tube with unknow
Tube with water
Ca+2
White ppt
Nothing happen
Cl-1
White ppt
Nothing happen
Fe+3
Red blood complex
Nothing happen
Cu+2
Deep blue complex
Nothing happen
• CaCl2(aq) + Na2CO3(aq)
Ca CO3 (s)
• Na Cl(aq) + Ag NO3 (aq)
Ag Cl (s)
+
+
2 NaCl (aq)
Na NO3 (aq)
Red blood complex
• Tetramine Cupper (II)
Gas releasing test.
• Carbonate test:
• Place a small amount of solid sodium carbonate- about the size of a
pea- in the bottom of a test tube.
• Add 3M HNO3 drop wise ( 1 to 2 drops at a time). Caution googles are
mandatory because a strong acid.
• Record your results
Part 1.
Ion
First drops of HNO3
After solid is completely
dissolved
CO3-2
Bubbling due to CO2
No bubbling.
Na2 CO3(aq) + HNO3(aq)
Na NO3 (aq) + H2O(l) + CO2 (g)
Sodium Carbonate and HCl.
Bubbling
Carbon dioxide
Part II Chemical composition of an unknown
solution.
• You will determine the chemical composition of the sample by
determining which cation and which anion are present in the sample.
• Remember the sample will have only one cation and one anion.
• 1. Place 10 drops of the unknown liquid into a test tube and add 3 M
Nitric acid.
• 2. Repeat adding 10 drops of the unknown liquid and add different
reagents in accordance with the following slides
• Record your results.
Part II Chemical composition of an unknow
sample (unknow 3)
• The cation present was ( name and formula)
• Fe+3 ( red blood complex with KSCN)
• The anion present was ( name and formula)
• Cl-1 because a white ppt of Ag Cl(s) was obtained with Ag NO3 (aq)
• The chemical formula for the unknown is:
• Fe Cl3
Part II Chemical composition of an unknow
sample (unknow 4)
• The cation present was ( name and formula)
• Cu+2( blue complex with NH4OH)
• The anion present was ( name and formula)
• Cl-1 because A white ppt of Ag Cl(s) was obtained with Ag NO3 (aq)
• The chemical formula for the unknown is:
• Cu Cl2
Problems
• 1 which ion is present in each of the following samples:
• a. The sample gives a white precipitate when treated with
• AgNO3 (silver nitrate)
• Cl-1
• b1. The sample gives a light purple color when placed in
• a hot flame. K+1
• b2. The sample gives a white ppt when added Na2 CO3
• Ca+2
• c. The sample gives off bubbles when treated with acid
• CO3-2
Problems.
• 2. Which ion or ions are shown to be absent from the following
samples?
• a. The solution does not turn red when treated with KSCN (potassium
thiocyanate) answer Fe+3 is absent
• b. The solution does not turn dark blue when treated with ammonia
(N H3) Cu+2 is absent
Problems
• 3. Using the equation for the reaction involved in the test for the
Calcium ion as example, write the equation for the test for chloride
ion. Be sure to indicate which is the precipitate
• Ca Cl2(aq) + 2 Ag NO3(aq)
--------------
2 Ag Cl (s) + Ca (NO3)2(aq)
• 4. What do you think would happen if you treated a sample of tap
water with some silver nitrate (Ag NO3). Explain.
• A white ppt of Ag Cl due to the present of Cl-1
A theorical example 1obtained by another student
testing cations and anions of another unknown
To test for
Add dropwise
Observed result
Ca+2
Na2CO3
No ppt
Cl-1
Ag NO3
White ppt
Fe+3
KSCN
No red blood complex
Cu+2
NH4 OH
Deep blue complex
CO3-2
HCl
No bubbling
K+
Na+
Flame test
No purple color
No yellow color
Which cation gave a positive result: Cu+2
Which anion gave a positive test Cl-1
Write the formula of the compound Cu Cl2
A theorical example 2 obtained by another
student testing cations and anions of another
unknown
To test for
Add dropwise
Observed result
Ca+2
Na2CO3
No ppt
Cl-1
Ag NO3
White ppt
Fe+3
KSCN
red blood complex
Cu+2
NH4 OH
No color
CO3-2
HCl
No bubbling
K+
Na+
Flame test
No purple color
No yellow color
Which cation gave a positive result: Fe+3
Which anion gave a positive test Cl-1
Write the formula of the compound Fe Cl3