Nigel Baldwin | Testing three blue solutions and other unknowns NTRG2511 @nigelbaldwin3184 | Uploaded April 2022 | Updated October 2024, 9 hours ago.
High School Chemistry
IGCSE Chemistry
Testing anions and cations in solution
Test-tube reactions
1 Three blue solutions labelled 1, 2 and 3
chloride and sulfate tests are carried out
Identify which is the sulfate, which is the chloride and which is the nitrate
Which metal cation produces blue solutions on the IGCSE Chemistry specification
2 Green and orange solutions labelled 4 and 5
addition of sodium hydroxide
and
chloride and sulfate tests are carried out
From the result of the addition of sodium hydroxide you should be able to confirm the identity of the metal cations as listed on the IGCSE Chemistry specification
Then you can identify which is the sulfate and which is the chloride from the results of the further tests
3 Two colourless solutions labelled 6 and 7
addition of a few drops of dilute sodium hydroxide
followed by excess of dilute sodium hydroxide
From the results of the addition of sodium hydroxide you can tell which of the two solutions contains aluminium ions.
The other colourless solution is known to contain either calcium or magnesium ions. Which further test could you carry out to tell which of these two metal ions is in fact present
The IGCSE Chemistry specification mentioned above is the Oxford AQA International GCSE Chemistry specification 9202
See section 3.4.3 Identification of ions
Results
1, 2 and 3 are all pale blue solutions and hence are all copper II salts given the limitations of our specification.
These solutions are also known to be either a nitrate, a chloride or a sulfate
Solution 1
white ppt with acidified barium chloride, therefore this must be a Sulfate
Solution 1 is copper II sulfate
Solution 2
No ppt with either acidified silver nitrate or acidified barium chloride
Therefore, this must be the Nitrate
Solution 2 is copper II nitrate
Solution 3
white ppt with acidified silver nitrate, therefore this must be a Chloride
Solution 3 is copper II chloride
Solution 4
Green solution
green ppt with dilute sodium hydroxide
Iron II
white ppt with acidified barium chloride
sulfate
Solution 4 is iron II sulfate
Solution 5
Orange solution
orange ppt with dilute sodium hydroxide
Iron III
white ppt with acidified silver nitrate
chloride
Solution 5 is iron III chloride
Solutions 6 and 7 were known to contain either magnesium, calcium or aluminium ions
Solution 6
white ppt with dilute sodium hydroxide
ppt did not dissolve in excess sodium hydroxide
therefore this solution contains either magnesium or calcium ions
A flame test should be carried out to differentiate the two possibilities
calcium gives a red orange coloured flame
magnesium does not produce a colour in a blue Bunsen burner flame
Solution 7
white ppt with dilute sodium hydroxide
ppt dissolved in excess dilute sodium hydroxide
therefore this solution contained aluminium ions
High School Chemistry
IGCSE Chemistry
Testing anions and cations in solution
Test-tube reactions
1 Three blue solutions labelled 1, 2 and 3
chloride and sulfate tests are carried out
Identify which is the sulfate, which is the chloride and which is the nitrate
Which metal cation produces blue solutions on the IGCSE Chemistry specification
2 Green and orange solutions labelled 4 and 5
addition of sodium hydroxide
and
chloride and sulfate tests are carried out
From the result of the addition of sodium hydroxide you should be able to confirm the identity of the metal cations as listed on the IGCSE Chemistry specification
Then you can identify which is the sulfate and which is the chloride from the results of the further tests
3 Two colourless solutions labelled 6 and 7
addition of a few drops of dilute sodium hydroxide
followed by excess of dilute sodium hydroxide
From the results of the addition of sodium hydroxide you can tell which of the two solutions contains aluminium ions.
The other colourless solution is known to contain either calcium or magnesium ions. Which further test could you carry out to tell which of these two metal ions is in fact present
The IGCSE Chemistry specification mentioned above is the Oxford AQA International GCSE Chemistry specification 9202
See section 3.4.3 Identification of ions
Results
1, 2 and 3 are all pale blue solutions and hence are all copper II salts given the limitations of our specification.
These solutions are also known to be either a nitrate, a chloride or a sulfate
Solution 1
white ppt with acidified barium chloride, therefore this must be a Sulfate
Solution 1 is copper II sulfate
Solution 2
No ppt with either acidified silver nitrate or acidified barium chloride
Therefore, this must be the Nitrate
Solution 2 is copper II nitrate
Solution 3
white ppt with acidified silver nitrate, therefore this must be a Chloride
Solution 3 is copper II chloride
Solution 4
Green solution
green ppt with dilute sodium hydroxide
Iron II
white ppt with acidified barium chloride
sulfate
Solution 4 is iron II sulfate
Solution 5
Orange solution
orange ppt with dilute sodium hydroxide
Iron III
white ppt with acidified silver nitrate
chloride
Solution 5 is iron III chloride
Solutions 6 and 7 were known to contain either magnesium, calcium or aluminium ions
Solution 6
white ppt with dilute sodium hydroxide
ppt did not dissolve in excess sodium hydroxide
therefore this solution contains either magnesium or calcium ions
A flame test should be carried out to differentiate the two possibilities
calcium gives a red orange coloured flame
magnesium does not produce a colour in a blue Bunsen burner flame
Solution 7
white ppt with dilute sodium hydroxide
ppt dissolved in excess dilute sodium hydroxide
therefore this solution contained aluminium ions
