8.2.2 - Laboratory Activity : Qualitative analysis of salts

Laboratory Activity 8.2.2: Qualitative analysis of salts

Aim: To confirm the presence of Mg²⁺ and NO^- ions in a salt sample, X

Material: » Magnesium nitrate powder » FeSO4 solution » Dilute sulphuric acid » Concentrate sulphuric acid » Sodium hydroxide solution » Ammonia solution

Apparatus: » Test tube » Test tube holder » Bunsen burner

Procedure:

	►	(A) Heat test 1. A spatula of compound is heated in a test tube, slowly at first and then strongly. 2. The observation and inferences made are recorded. Experiment Observation Inference (a) the colour of gases released (b) the effect on damp litmus (c) the effect on glowing splint
	►	(B) Brown ring test 1. Add water to compound X to make solution. 2. Add 2cm3 of dilute sulphuric acid and iron(II) sulphate, FeSO4 solution to the solution. 3. Concentrated sulphuric acid is then added slowly along the wall of the tilted test tube to the mixture without shaking.
	►	(C) Compound X is dissolved in distilled water. The solution is divided into 2 portion. 1. Sodium hydroxide solution is added to the first portion of solution X until in excess. 2. Aqueous ammonia is added to the second portion of solution until in excess.

Results:

	►	(A) Heat test ○ A spatula of compound is heated in a test tube, slowly at first and then strongly. The observation and inferences made are recorded. Experiment Observation Inference (a) the colour of gases released Brown gas. NO2 released. (b) the effect on damp litmus Blue litmus turned red. Acidic gas released. (c) the effect on glowing splint Rekindles glowing splint O2 released. ○ Probably NO3- present.
	►	(B) Brown ring test. ○ Brown ring formed at the middle section of the solution mixture in the test tube, nitrate ion present.
	►	(C) Compound X is dissolved in distilled water. ○ Experiment Observation Inference (a) Add with NaOH White precipitate, insoluble in excess NaOH May be Ca2+ or Mg2+ (b) Add with aqueous ammonia White precipitate, insoluble in excess NaOH May be Pb2+, Al3+ or Mg2+ ○ Probably NO3- present.

Conclusion:

►

The ions present in salt X are confirmed as Mg2+ and NO3- ions

↶ 8.2 Qualitative analysis of salts

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