Working Plan : Investigation of the content of oxygen absorber
Objective:
To determine the content of oxygen absorber in a moon cake package.
Introduction:
According to the information on the internet, there are iron powder (or iron compound), sodium chloride and sodium carbonate. Then we are going to use different methods to test whether those substances are present in the oxygen absorber or not.
Procedures:
A. Test for iron powder
1. Open a pack of oxygen absorber, and place the substances inside package on the white tile.
2. Place a magnet wrapped with paper above the sample on the white tile.
3. Some of the substances are attracted by the magnet, and add them in warm 1M H2SO4. (If nothing is drawn, add about 1/4 of the sample into 1M H2SO4 )
4. Add 0.4M NaOH into the mixture of (2) drop by drop by dropper until a green precipitate occurs.
Expectation:
The substances that are attracted by magnet would be iron powders.
When those iron powders dissolve into ...
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Procedures:
A. Test for iron powder
1. Open a pack of oxygen absorber, and place the substances inside package on the white tile.
2. Place a magnet wrapped with paper above the sample on the white tile.
3. Some of the substances are attracted by the magnet, and add them in warm 1M H2SO4. (If nothing is drawn, add about 1/4 of the sample into 1M H2SO4 )
4. Add 0.4M NaOH into the mixture of (2) drop by drop by dropper until a green precipitate occurs.
Expectation:
The substances that are attracted by magnet would be iron powders.
When those iron powders dissolve into the sulphuric acid, a green solution is obtained. Iron is reacted with acid and form green iron(II) ions. A yellow solution may formed, as iron(III) ions are presented.
A dirty green precipitate formed when sodium hydroxide solution is added to the mixture, it is used to show the presence of iron ions. If there are iron(III) ions, a reddish brown precipitate is formed.
1.Acidified the Potassium manganate(VII) solution by adding the 1M nitric acid.
2. Open a pack of oxygen absorber,and pour the substances into the test tube with the 1M sulphuric acid.
3. Add the acidified potassium manganate(VII) solution into a test tube drop by drop.Record the observable change of the solution.
Expection:
The acidified potassium manganate(VII) solution would be decolourized.As the oxygen absorber contain iron which react with the acid to form iron(II) ions,then a reducing agent is presented.Then the purple manganate ion is reduced by the iron(II) ions to form colourless manganate(II) ions.
B. Test for sodium chloride
1. Open a pack of oxygen absorber, and dissolve half of sample in water, and place the other half into a test tube.
2. To construct a filtration set-up. Filter the sample solution until there is no residue in the solution.
3. To acidified the 0.05M AgNO3 by adding 1M HNO3.
4. Add the acidified AgNO3 solution into the sample solution by dropper. Record the observable change of the solution.
Expectation:
A white precipitate is formed if chloride ions are presented in the sample.
5. Dip the platinum wire into the test tube with 1M HCl.
6. Heat the wire with non-luminous flame until no characteristic coloured flame is observed.
7. Dip the cleaned wire into the test tube with the other sample
8.Heat the wire with the solid sample in non-luminous flame. Then record the flame colour.
Expectation:
If sodium ions are presented, a golden-yellow flame would be observed.
C. Test for carbonate
1. Open a pack of oxygen absorber and put it into a test tube
2. Add about 5 cm3 lime water into another test tube.
3. Add 1M sulphuric acid into the test tube which place with oxygen absorber.
4. Stopper the test tube with oxygen absorber and sulphuric acid, then place the delivery tube between it and the test tube with lime water.
5. Record the observable change.
Expection:
If carbonate is present in the oxygen absorber, carbon dioxide would be produced when dilute sulphuric acid is added. Then, the lime water would change from colourless to milky.
The iron powder would be the main content of oxygen absorber for its function, the rusting of iron allow oxygen and moisture to enter but does not allow they to leak out.
