ICSE Class 9 Chemistry Practical Chemistry

Practical Chemistry

Latest Syllabus For Std. Ix - Practical Work

Internal Assessment of Practical Work

Candidates will be asked to observe the effect of reagents and/or of heat on substances supplied to them. The exercises will be simple and may include the recognition and identification of certain gases listed below.

Gases: Hydrogen, Oxygen, Carbon dioxide, Chlorine, Hydrogen chloride, Sulphur dioxide, Hydrogen sulphide, Ammonia, Water vapour, Nitrogen dioxide.

Candidates are expected to have completed the following minimum practical work.

Simple Experiments On:

1. Heat the given (unknown) substance, make observations - Identify any products and make deductions where possible.

(a) copper carbonate, zinc carbonate (b) washing soda, copper sulphate crystals

(c) zinc nitrate, copper nitrate, lead nitrate (d) ammonium chloride, iodine, ammonium dichromate

2. Add dilute sulphuric acid to the unknown substance - Warm if necessary, make observation, identify the product and make deductions.

(a) a sulphide (b) a carbonate (c) a metal

3. Apply the flame test - to identify the metal in the unknown substance.

(a) a sodium salt (b) a potassium salt (c) a calcium compound

4. The percentage composition - of a mixture of powdered salt and water-washed sand. The experiment would test techniques in dissolving, filtering or decanting, washing and weighing. It may be counted out as taking too much time. The weaknesses could be met by supplying a given weight of the mixture; also by choosing sand of such grain size that filtering or decanting will not be slow and yet not so large that separation of salt and sand cannot be done simply by sorting out mechanically the sand from the salt. The experiment should take about 20 minutes using 10g mixture (4g sand, 6g salt).

5. Simple experiments - based on hard water and soft water - identification of hardness - simple softening - by heating the temporary hard water, using washing soda and advantage of using detergents over soap in hard water.

6. Find out the sources of pollution of water bodies in the locality and determine the quality of water.

Practical Chemistry Chart

I. Identification Of Gases

Neutral Gases

1. Water Vapour

Colour: Colourless

Odour: Odourless

Litmus Test: Neutral to litmus.

Tests For The Gas:

Turns white anhydrous copper sulphate - blue.

\[\text{CuSO}_4 \text{[white]} + 5\text{H}_2\text{O} \to \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \text{[blue]}\]

Turns blue cobalt chloride paper - pink.

\[\text{CoCl}_2 \text{[blue]} + 2\text{H}_2\text{O} \to \text{CoCl}_2 \cdot 2\text{H}_2\text{O} \text{[pink]}\]

2. Hydrogen [H2]

Colour: Colourless

Odour: Odourless

Litmus Test: Neutral to litmus.

Tests For The Gas:

Burning wooden splinter is - extinguished in hydrogen.

Hydrogen burns with a - pale blue flame producing a 'pop' sound.

\[2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O} \text{[on kindling]}\]

3. Oxygen [O2]

Colour: Colourless

Odour: Odourless

Litmus Test: Neutral to litmus.

Tests For The Gas:

Rekindles - a glowing wooden splinter.

Absorbed in colourless alkaline pyrogallol solution which turns - brown.

Acidic Gases

4. Carbon Dioxide [CO2]

Colour: Colourless

Odour: Odourless

Litmus Test: Moist blue litmus turns faint red.

Tests For The Gas:

Burning wooden splinter is - extinguished in carbon dioxide.

On passage through lime water, it turns lime water - milky.

\[\text{Ca(OH)}_2 + \text{CO}_2 \to \text{CaCO}_3 \downarrow \text{[white ppt. - insoluble]} + \text{H}_2\text{O}\]

The milkiness disappears - on passage of excess carbon dioxide.

\[\text{CaCO}_3 + \text{H}_2\text{O} + \text{CO}_2 \to \text{Ca(HCO}_3)_2 \text{[soluble]}\]

The gas has no effect on acidified KMnO4 or K2Cr2O7 solution.

5. Sulphur Dioxide [SO2]

Colour: Colourless

Odour: Suffocating

Litmus Test: Moist blue litmus turns red.

Tests For The Gas:

Burning wooden splinter is - extinguished in sulphur dioxide.

On passage through lime water, it turns lime water - milky.

\[\text{Ca(OH)}_2 + \text{SO}_2 \to \text{CaSO}_3 \downarrow \text{[white ppt. - insoluble]} + \text{H}_2\text{O}\]

The milkiness disappears - on passage of excess sulphur dioxide.

\[\text{CaSO}_3 + \text{H}_2\text{O} + \text{SO}_2 \to \text{Ca(HSO}_3)_2 \text{[soluble]}\]

Turns acidified potassium permanganate from - pink to clear colourless.

\[2\text{KMnO}_4 + 2\text{H}_2\text{O} + 5\text{SO}_2 \to \text{K}_2\text{SO}_4 + 2\text{MnSO}_4 + 2\text{H}_2\text{SO}_4\]

Turns acidified potassium dichromate from - orange to clear green.

\[\text{K}_2\text{Cr}_2\text{O}_7 + \text{H}_2\text{SO}_4 + 3\text{SO}_2 \to \text{K}_2\text{SO}_4 + \text{Cr}_2(\text{SO}_4)_3 + \text{H}_2\text{O}\]

6. Chlorine [Cl2]

Colour: Greenish yellow

Odour: Pungent

Litmus Test: Moist blue litmus turns red and then gets bleached.

Tests For The Gas:

Turns moist blue litmus red and then - bleaches it.

\[\text{Cl}_2 + \text{H}_2\text{O} \to \text{HCl} + \text{HOCl}; \quad \text{HOCl} \to \text{HCl} + [\text{O}] \text{[nascent]}\]

Colouring matter [litmus] + [O] - Colourless or bleached product

Turns moist starch iodide paper [KI + starch solution] - blue black.

\[\text{Cl}_2 + 2\text{KI} \to 2\text{KCl} + \text{I}_2\]

Starch + I2 - Blue black colour

Teacher's Note

Understanding gas identification helps in recognizing pollutants in air we breathe and in detecting substances in everyday applications like water purification and food preservation.

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