2. Explain how you would test an unknown solution to conrm the presence of lead

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2. Explain how you would test an unknown solution to conrm the presence of lead (II) ion in a mixture that contains both lead (II) and copper (II)ions.

I put: To test for the presence of lead (II) ion in the solution by adding HCl to the mixture. The lead (II) ion will form a white precipitate while the copper (II) will have no reaction. Doing this would confirm the presence of lead(II) ion.

3. Explain how you would test an unknown solution to conrm the presence of nickel (II) ion in a mixture that contains both lead (II) and nickel (II) ions.

I put: To test for the presence of nickel (II) ion I would add NaOH to the solution which would form a white precipitate. I would then add NH3 to the mixture and lead (II) ion will have no change of the white precipitate while the presence of nickel(II) ion will disolve the white precipitate and produce a violet solution. This would confirm the presence of nickel (II) ion in the mixture.

4. Based on the student’s data, explain why it would or would not be possible to conrm the presence of copper (II) and nickel (II) ions in a mixture that contains both ions.

5. Procedures must be followed carefully when doing qualitative analysis. Consider your experimental observations of the reactions of the lead (II) ion and the information for the ion in the table at the beginning of the assignment in the lab manual. Explain how a student could have an unknown mixture that contains lead (II) ion and not be able to conrm it if the amounts of reagents are not carefully measured.

6. Suppose a solution is tested for nitrite ion by adding 3M sulfuric acid and heating, repeating this process until no further reaction occurs. This solution is then analyzed for nitrate ion by adding iron (II) sulfate solution and more sulfuric acid, heating the test tube and its contents. The nitrate ion reaction is positive. In this case, is it accurate to state that nitrate ion was present in the original solution? Briey explain, referencing specific chemical reactions to support your explanation.

7. A solution is known to contain nitrate, nitrite and sulfate ions. Using the reagents that were used in the experiment, which of these ions can be positively identied? List the reactions you would use to test this solution and the results you would observe if all three ions were present.

2. Explain how you would test an unknown solution to conrm the presence of lead (II) ion in a mixture that contains both lead (II) and copper (II)ions.

3. Explain how you would test an unknown solution to conrm the presence of nickel (II) ion in a mixture that contains both lead (II) and nickel (II) ions.

4. Based on the student’s data, explain why it would or would not be possible to conrm the presence of copper (II) and nickel (II) ions in a mixture that contains both ions.

5. Procedures must be followed carefully when doing qualitative analysis. Consider your experimental observations of the reactions of the lead (II) ion and the information for the ion in the table at the beginning of the assignment in the lab manual. Explain how a student could have an unknown mixture that contains lead (II) ion and not be able to conrm it if the amounts of reagents are not carefully measured.

A student studied some reactions involving Pb2+ion, copper(II ion (Cu2+), and nickel(II) ion (Ni h). The student first observed the behavior of individual solutions of Pb(NO3)2, copper (II) nitrate Cu(NO3) and nickel II) nitrate, NiNO3)2, interacting individually with HCl solution and then individually with 1M sodium hydroxide solution (NaoH). The student also added an aqueous ammonia solution (NH3) to the reaction mixtures, following the addition of NaoH solution. The student's data are shown in the table. Test Solution Known Solution Added Observations Pb(NO3)2 HCI A white precipitate formed. The precipitate dissolved upon addition of more HCl solution. Pb(NO3)2 NaOH A white precipitate formed Pb(NO3)2 NaOH solution. NH3 No change was evident in the white precipitate. Cu(NO3)2 HC1 No reaction NaOH Cu(NO3) A blue precipitate formed Cu(NO3) 2-NaOH solution. NH The precipitate dissolved, producing a deep blue solution Ni(NO3)2 HC1 No reaction Ni(NO3) NaOH A white precipitate formed Ni(NO3)2 NaOH solution NH The precipitate dissolved, producing a violet solution

Explanation / Answer

4. Based on the student’s data, explain why it would or would not be possible to conrm the presence of copper (II) and nickel (II) ions in a mixture that contains both ions.

A: In both the case, the experiment with adding HCl gives no reaction, with NaOH both the solution produces a white precipitate and the resulted precipitate will dissolve in NH3. So, in these three experimental conditions, there is no distinct observations found in case of Copper (II) and Nickel (II). So, it is not possible to tell whether we have Cu(II) or Ni(II).

5. Procedures must be followed carefully when doing qualitative analysis. Consider your experimental observations of the reactions of the lead (II) ion and the information for the ion in the table at the beginning of the assignment in the lab manual.

A: The given experimental procedure is qualitative analysis not quantitative. By, this method it is not possible to quantify the amounts.

6. Suppose a solution is tested for nitrite ion by adding 3M sulfuric acid and heating, repeating this process until no further reaction occurs. This solution is then analyzed for nitrate ion by adding iron(II) sulfate solution and more sulfuric acid, heating the test tube and its contents. The nitrate ion reaction is positive. In this case, is it accurate to state that nitrate ion was present in the original solution? Briey explain, referencing specific chemical reactions to support your explanation.

A: There is no reaction possible for nitrite ions with Sulfuric acid.

When you add sulfuric acid to nitrate ions in presence of concentrated sulfuric acid you will see the following positive test for nitrate ions. This test is called brown ring test. The overall reaction is the reduction of the nitrate ion by iron(II) which is oxidised to iron(III) and formation of a nitrosonium complex where nitric oxide is oxidised to NO+.

    2HNO3+ 3H2SO4 + 6FeSO4 --->> 3Fe2(SO4)3 + 2NO + 4H2O
    [Fe(H2O)6]SO4 + NO = [Fe(H2O)5(NO)]SO4+ H2O


7. A solution is known to contain nitrate, nitrite and sulfate ions. Using the reagents that were used in the experiment, which of these ions can be positively identied? List the reactions you would use to test this solution and the results you would observe if all three ions were present.

nitrite ion Test:

A common nitrite test can be performed by adding 4 M sulfuric acid to the sample until acidic and then adding 0.1 M iron(II) sulfate to the solution. A positive test for nitrite is indicated by a dark brown solution, arising from the iron-nitric oxide complex ion.

Test for Nitrate Ions: NO3-
Add the nitrate to sodium hydroxide solution, then add powdered aluminium. The nitrate ion is reduced by the aluminium,
and ammonia gas is given off. Use damp red litmus paper to test the gas. If the litmus paper turns blue the gas is ammonia and the test for nitrate ions is positive.

The aluminium reduces the nitrate ion (NO3-) to an ammonium ion (NH4+). The ammonium ion reacts with hydroxide to produce ammonia gas and water (see alkalis).

NH4+(aq) + OH-(aq) ---> NH3(g) + H2O(l)

Sulfate Ion Test.
A white precipitate of barium sulfate is formed in the presence of hydrochloric acid when a solution of barium chloride is added to a solution containing sulfate ions. The equation for the reaction is:
Ba+2(aq) + SO4-2(aq) BaSO4(s) White precipitate

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2. Explain how you would test an unknown solution to conrm the presence of lead

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