Test Procedure

You are provided with Substance P. Carry out the tests below and write down your observations and inferences in the spaces provided below.

(a) Describe the appearance of solid p.
(b) Place about one third of the substance in a dry test-tube and heat it strongly
(c) Place the remaining amount of substance p in a boiling tube, add about 10cm3 of distilled water and shake well. Retain the mixture for tests in (d) below
(d) Use about 2cm3 of portions of the mixture obtained in c for tests below.
1. i. Add 2 to 3 drops of aqueous barium nitrate solution to the mixture
2. ii. Add 5 drops of dilute nitric (v) acid to the mixture
3. iii. Add to the mixture, aqueous sodium hydroxide dropwise until in excess

Tips: To start, ...click on boiling tube in the display rack to select it before placing the sample.
Follow the procedure sequentially and the sytem monitor instructions.

Tips on the system color code

Colourless Solution

White Precipitate

Workbench

VIRTUAL WORKBENCH MONITOR Selected: None

System Initialised. Select boiling tube to start step 1.

Main

T₁

T₂

T₃

T₄

T₅

STUDENT LABORATORY WORKBOOK

Procedure	Observations	Inferences
(a) Ammonia Test - Describe the appearance when ammonia is added dropwise
(b) Ammonia in Excess - Add ammonia in excess to the precipitate
(c) NaOH Test - Add 2M NaOH dropwise to portion T₂
(d) NaOH in Excess - Add NaOH in excess to the precipitate
(e) Anion Test - Add BaCl₂ to portion T₅

OFFICIAL MARKING SCHEME & EXPECTED RESPONSES

Procedure	Observations	Inferences
(a) Ammonia Test	White precipitate (1 mark)	Mg²⁺ present / White ppt is Mg(OH)₂ (1 mark)
(b) Ammonia in Excess	White precipitate remains insoluble (1 Mark)	Mg(OH)₂ is insoluble in excess ammonia (1 mark)
(c) NaOH Test	White precipitate (1 mark)	Mg²⁺ present / White ppt is Mg(OH)₂ (1 mark)
(d) NaOH in Excess	White precipitate remains insoluble (1 mark)	Mg(OH)₂ is insoluble in excess NaOH (1 mark)
(e) Barium Chloride Test	White precipitate formed (1 mark)	SO₄²⁻ present / White ppt is BaSO₄ (1 mark)
		*Identity of Salt: Magnesium Sulphate (MgSO₄)*

Sample Test Paper 17