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Complete Chemistry Practical Handbook - High School Chemistry Form 4, Form 3, Form 2, Form 1

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CHEMISTRY REVISION QUESTIONS

Click to Attempt Form 3 Chemistry Questions

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SPECIFIC OBJECTIVES OF CHEMISTRY PRACTICALS

i. To test if the student is able to select and handle apparatus for use in an experimental work
ii. To test if the student is able to use his/her theoretical understanding of chemistry to make accurate observations and draw conclusions from those observations
iii. To test if the student is able to make accurate measurements

AREAS COMMONLY TESTED IN PRACTICAL;
1. Qualitative analysis (organic and inorganic)
2. Quantitative analysis
3. Graphical work

A) QUALITATIVE ANALYSIS

Refers to the process of carrying out chemical tests on substances with the sole aim of identifying them
TO BE ABLE TO GET GOOD RESULTS;
a) Accurately identify the test reagents
b) Identify what these reagents test
c) Predict the expected results

I. INORGANIC TESTS

Test for cations (12 cations involved; Na+, K+, NH4+, Ca2+, Ba2+, Mg2+, Al3+, Zn2+, Pb2+, Cu2+, Fe2+ and Fe3+)

1) Addition of NaOH (Sodium Hydroxide) drop wise until in excess

Observation Inference
White precipitate, soluble in excess Zn2+, Al3+, Pb2+
White precipitate, insoluble in excess Mg2+, Ca2+
No white precipitate Na+, K+, NH4+ present
Zn2+, Al3+, Pb2+, Mg2+, Ca2+ absent
Blue precipitate, insoluble in excess Cu2+
Green precipitate, insoluble in excess Fe2+
Brown precipitate, insoluble in excess Fe3+

2) Addition of aqueous Ammonia drop wise, until in excess

Observation Inference
White precipitate, soluble in excess Zn2+
White precipitate, insoluble in excess Al3+, Pb2+, Mg2+
No white precipitate Na+, K+, Ca2+ present
ZnZn2+, Al3+, Pb2+, Mg2+ Absent
Light blue precipitate, soluble in excess to give a deep blue solution Cu2+
Green precipitate, insoluble in excess Fe2+
Brown precipitate, insoluble in excess Fe3+

3) Dip a nichrome wire into the solution and burn in a non luminous flame (Flame test for cations)

Observation Inference
Burns with a yellow flame Na+
Burns with a red flame Ca2+
Burns with a purple flame K+
Burns with a white flame Mg2+

4) Addition of three drops of H2SO4 / Na2SO4 / K2SO4

Observation Inference
White precipitate Ca2+, Ba2+, Pb2+

5) Addition three drops of HCl / NaCl / KCl

Observation Inference
White precipitate Pb2+, Ag+

6) Addition of two drops of potassium iodide

Observation Inference
Yellow precipitate Pb2+

TEST FOR ANIONS (SIX ANIONS; SO42-, SO32-, CO32-, Cl-, NO3- and HCO3-)

1) Addition of two drops of barium nitrate

Observation Inference
White precipitate SO42-, SO32-, CO32-

2) Addition of two of drops of barium nitrate followed by five drops of nitric (V) acid

Observation Inference
White precipitate, dissolves upon addition of nitric (V) acid SO32-, CO32-
White precipitate, insoluble upon addition of nitric (V) acid SO42-

3) Addition of two drops of acidified barium nitrate

Observation Inference
White precipitate SO42-

4) Addition of three drops of lead (II) nitrate

Observation Inference
White precipitate SO42-, SO32-, CO32-, Cl-

5) Addition of two drops of lead (II) nitrate followed by five drops of nitric (V) acid

Observation Inference
White precipitate, soluble on addition of nitric (V) acid SO32-, CO32-
White precipitate, insoluble upon addition of nitric (V) acid SO42-, Cl-

6) Addition of two drops of lead (II) nitrate, followed by warming

Observation Inference
White precipitate, soluble upon warming Cl-
White precipitate, insoluble upon warming SO42-, SO32-, CO32-

7) Addition of two drops of acidified lead (II) nitrate

Observation Inference
White precipitate, soluble upon warming SO42-, Cl-

8) Addition of two drops of acidified potassium dichromate (VI)

Observation Inference
Colour of H+/K2Cr2O7 turns from orange to green SO32-
H+/K2Cr2O7 retains its orange colour CO32-

9) Take about half of the solid provided into a dry test tube and heat it gently then strongly

Observation Inference
Colourless liquid formed on upper cooler parts of the test tube The solid is hydrated
Blue litmus paper turns red and red litmus paper remains red Acidic gas produced
Red litmus paper turns blue and blue litmus paper remains blue NH4+
Bubbles of colourless gas that blows off a burning splint CO32- / HCO3-
Brown fumes NO3-
Relights a glowing splint NO3-
Residue white when cold and yellow when hot ZnO formed
White solid formed on cooler parts of test tube Contains a solid that sublimes

10) Put the solid into a boiling tube, add water, shake, if residue is formed - filter. Transfer the residue from filter paper using a spatula into a boiling tube, add about 2 ml of nitric (V) acid

Observation Inference
Bubbles of colourless gas.
The solid dissolves
SO32-, CO32-

Chemistry Practicals Examples

Example 1:

You are provided with;
  1. Solid Q suspected to be Zinc Sulphate
  2. 2 M Sodium hydroxide solution
  3. 2 M Aqueous ammonia
  4. 2 M Nitric (V) acid
  5. 0.5 M Barium Chloride solution
  6. Distilled water
Using the provided chemicals, write down three tests and expected observations to completely confirm the identity of solid Q
Test 1
Put solid Q into a boiling tube, add 10 ml of distilled water, then shake to dissolve solid Q. Divide the solution formed into 3 portions; To the 1st portion, add sodium hydroxide drop wise until in excess

Expected observation(s)

White precipitate, soluble in excess

Test 2
To the 2nd portion, add aqueous ammonia drop wise until in excess

Expected observation(s)

White precipitate, soluble in excess

Test 3
To the 3rd portion, add two drops of barium chloride, followed by about 10 ml of nitric (V) acid

Expected observation(s)

White precipitate formed upon adding barium chloride, the white precipitate do not dissolve when acid is added
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