Sample Test 8

Analysis of Solid E

Test Procedure

You are provided with solid D. Carry out the tests below & write down your observations and inferences in the spaces provided.

  • (a) Place about half of solid D in a clean dry test tube and heat strongly. Test any gases produced with both blue and red litmus papers.
  • (b) Place the remaining solid D in a boiling tube. Dissolve in about 12cm3 of distilled water. Divide the resulting solution into 4 portions: T1, T2, T3& T4
    • (i) To the 1st portion, add two drops of universal indicator and determine its pH using PH chart
    • (ii) To the 2nd portion, add 2M ammonium hydroxide solution dropwise until in excess
    • (iii) To the 3rd portion, add 3-4 drops of potassium Iodide solution provided
    • (iv) To the 4th portion, add 4-5 drops of Barium Chloride solution, followed by 2cm3 of dilute hydrochloric acid.

    • 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

    White

    Brown

Workbench

VIRTUAL WORKBENCH MONITOR Selected: None
System Initialised. Start step 1: Place about half of solid D in clean dry test tube.
T0

B.T
T1
T2
T3
T4

STUDENT LABORATORY WORKBOOK

Procedure Observations Inferences
(a) About half of solid D in a clean dry test tube + heated strongly + Tested gases produced with both blue and red litmus papers.
(b) Placed the remaining solid D in a boiling tube + Dissolved in about 12cm3 of distilled water.
Divided into 4 portions: T1, T2, T3 & T4
(i) To the 1st portion + 2 drops of universal indicator. Determine its pH using PH chart
(ii) To the 2nd portion + 2M NH4OH solution dropwise until in excess
(iii) To the 3rd portion + 3 to 4 drops of KI solution provided
(iv) To the 4th portion + 4 to 5 drops of BaCl solution, followed by 2cm3 of dilute HCl.

OFFICIAL MARKING SCHEME & EXPECTED RESPONSES

Procedure Observations Inferences
(a) About half of solid D in a clean dry test tube + heated strongly + Tested gases produced with both blue and red litmus papers. Colourless liqud forms on the cooler parts of the test tube/colourless vapour condenses on the cooler parts of the test tube.

colourless gas with a choking/pungent smell that turns blue litmus paper red & no effect on red litmus paper

(1 mark) 		Acidic gas evolved (tied to blue litmus paper turning red)

Hydrated compound / contains water of crystallisation

(1 mark)
(b) Placed the remaining solid D in a boiling tube + Dissolved in about 12cm3 of distilled water.
Divided into 4 portions: T1, T2, T3 & T4
(i) To the 1st portion + 2 drops of universal indicator. Determine its pH using PH chart
 pH 1,2 or 3

(1 mark) 		the solution is strongly acidic

(1 mark)
(ii) To the 2nd portion + 2M NH4OH solution dropwise until in excess Brown precipitate insoluble in excess

(1 mark) 		Fe3+ present

(1 mark)
(iii) To the 3rd portion + 3 to 4 drops of KI solution provided Brown solution/black solid formed

solution changes from yellow to brown

(1 mark) 		Iodide ions oxidized to iodine

Solution E contains oxidising agent

(1 mark)
(iv) To the 4th portion + 4-5 drops of BaCl2 solution, followed by 2cm3 of dilute HCl. White precipitate settles at the bottom of the test tube

No effervescence

(Two observations must be mentioned to be awarded full marks)

(1 mark) 		SO42- present

(1 mark)

Identity of solid D: Iron (iii) Sulphate