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⁺, NH^⁴⁺, Ca^²⁺, Ba^²⁺, Mg^²⁺, Al^³⁺, Zn^²⁺, Pb^²⁺, Cu^²⁺, Fe^²⁺ and Fe^³⁺)

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; SO₄^2-, SO₃^2-, CO₃^2-, Cl^-, NO₃^- and HCO₃^-)

1) Addition of two drops of barium nitrate

Observation	Inference
White precipitate	SO₄^2-, SO₃^2-, CO₃^2-

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	SO₃^2-, CO₃^2-
White precipitate, insoluble upon addition of nitric (V) acid	SO₄^2-

3) Addition of two drops of acidified barium nitrate

Observation	Inference
White precipitate	SO₄^2-

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

Observation	Inference
White precipitate	SO₄^2-, SO₃^2-, CO₃^2-, 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	SO₃^2-, CO₃^2-
White precipitate, insoluble upon addition of nitric (V) acid	SO₄^2-, 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	SO₄^2-, SO₃^2-, CO₃^2-

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

Observation	Inference
White precipitate, soluble upon warming	SO₄^2-, Cl^-

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

Observation	Inference
Colour of H⁺/K₂Cr₂O₇ turns from orange to green	SO₃^2-
H⁺/K₂Cr₂O₇ retains its orange colour	CO₃^2-

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	CO₃^2- / 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	SO₃^2-, CO₃^2-

Chemistry Practicals Examples

Example 1:

You are provided with;

Solid Q suspected to be Zinc Sulphate
2 M Sodium hydroxide solution
2 M Aqueous ammonia
2 M Nitric (V) acid
0.5 M Barium Chloride solution
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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Chemistry Practical Handbook - High School Chemistry Form 4, Form 3, Form 2, Form 1

CHEMISTRY REVISION QUESTIONS

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SPECIFIC OBJECTIVES OF CHEMISTRY PRACTICALS

A) QUALITATIVE ANALYSIS

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

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

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

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

5) Addition three drops of HCl / NaCl / KCl

6) Addition of two drops of potassium iodide

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

1) Addition of two drops of barium nitrate

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

3) Addition of two drops of acidified barium nitrate

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

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

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

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

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

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

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

Chemistry Practicals Examples

Expected observation(s)

Expected observation(s)

Expected observation(s)

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Test for cations (12 cations involved; Na⁺, K⁺, NH^⁴⁺, Ca^²⁺, Ba^²⁺, Mg^²⁺, Al^³⁺, Zn^²⁺, Pb^²⁺, Cu^²⁺, Fe^²⁺ and Fe^³⁺)

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

TEST FOR ANIONS (SIX ANIONS; SO₄^2-, SO₃^2-, CO₃^2-, Cl^-, NO₃^- and HCO₃^-)