CHEMISTRY: To analyse the given salt for acidic and basic radicals. (Example No. 1)

Saturday, October 22, 2016

To analyse the given salt for acidic and basic radicals. (Example No. 1)

EXPERIMENT	OBSERVATIONS	INFERENCE
1.PHYSICAL EXAMINATION: a) Colour of the given salt. b) Noted the smell of the salt.	White No specific odour	Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺, Fe³⁺, absent. NH₄⁺, S^2- and CH₃COO^-may be absent.
2. DRY HEAT TEST Heated a pinch of the salt in a dry test tube	A reddish brown gas evolved which turned FeSO₄ solution black.	NO₃^- may be present.
3.DIL. SULPHURIC ACID TEST Treated a pinch of salt with dil. H₂SO₄ and warmed.	No gas evolved.	CO₃^2-, S^2-, SO₃^2-, NO₂^-, may be absent.
4.CONC. SULPHURIC ACIS TEST Heated a pinch of the salt with conc. Sulphuric acid and added to it a paper pellet.	A reddish brown gas evolved which turned FeSO₄ solution black.	NO₃^- may be present.
5.CONFIRMATORY TEST FOR NITRATE a) Copper chips test. Heated a pinch of the salt with conc. Sulphuric acid and a few copper chips. b) Ring test. To 2-3 mL of the salt solution, added freshly prepared FeSO₄ solution. Then added conc. Sulphuric acid along the sides of the test tube.	Reddish brown gas evolved. A dark brown ring formed at the junctions of the two liquids.	NO₃^- confirmed. NO₃^- confirmed.
6.HEATED A PINCH OF SALT WITH CONC. NaOH SOLUTION	No ammonia gas evolved.	NH₄⁺ absent.
7.TO A PART OF THE O.S. ADDED 1-2 mL OF Dil. HCl	No ppt. formed.	Group I absent. (Pb²⁺ absent)
8.TROUGH A PART OF THE ABOVE SOLUTION, PASSED H₂S GAS	No ppt. formed.	Group II absent (Pb²⁺, Cu²⁺, As³⁺ absent)
9. TO THE REMAINING SOLUTION, ADDED A PINCH OF NH₄Cl. BOILED THE SOLUTION, COOLED IT AND ADDED EXCESS OF NH₄OH SOLUTION.	No ppt. formed.	Fe³⁺, Al³⁺, absent.
10.THROUGH A PART OF THE ABOVE SOLUTION, PASSED H₂S GAS	No ppt. formed.	Group IV absent. (Zn²⁺, Mn²⁺, Co²⁺ and Ni²⁺ absent)
11. TO THE REMAINING AMMONICAL SOLUTION ADDED (NH₄)₂CO3 SOLUTION.	White ppt. formed.	Group V present. (Ca²⁺, Ba²⁺, Sr²⁺ may be present)
12. CONFORMATORY TEST Filtered the above white ppt. dissolved the ppt. in hot dilute acetic acid a) Pot. Chromate test. To one part of the above solution, added a few drops of pot. Chromate solution. b) Flame test. Performed flame test with the salt.	Yellow ppt. formed. Persistent grassy green flame on prolonged heating.	Ba²⁺ confirmed. Ba²⁺confirmed.