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Aim
To study the properties of acids and bases (dilute HCl and dilute NaOH) on the basis of their reaction with
(a) Litmus solution (Blue/Red)
(b) Zinc metal
(c) Solid sodium carbonate
Materials Required
A test tube stand, test tubes, matchbox, test tube holder, droppers, a bent delivery tube, burner and cork.
Chemicals required: Dilute hydrochloric acid, dilute sodium hydroxide, blue litmus solution, red litmus solution, zinc metal granules or powdered zinc, solid sodium carbonate and freshly prepared lime water.
Equations
(Equations on the white pages only)
Procedure
(A) Properties of Hydrochloric Acid
Litmus Test
Experiment: Take two clean test tubes. Pour 1 mL of dilute HCl solution into each test tube. Pour a drop of blue litmus in one test tube and a drop of red litmus solution into the second test tube.
Observation: Blue litmus solution turns red in the first test tube.
The red litmus solution shows no change in the second test tube.Inference: Dil. HCl shows an acidic character.
Reaction with Zinc Metal
Experiment: Take 1 mL of dilute HCl in a clean test tube. Add a small piece of zinc metal/ zinc powder in it.
Light a matchstick and bring it near the mouth of the test tube, remove the thumb and observe.Observation: Zinc metal reacts with the acid. The test tube becomes warm and pressure is exerted on the thumb due to the release of a gas.
The matchstick burns with a pop sound.Inference: Hydrogen gas always burns with a pop sound when a lighted matchstick is introduced in it.
Reaction with Sodium Carbonate
Experiment: Take a clean test tube. Add 2 mL of dilute HCl. Now add 1g/pinch of sodium carbonate in it. Immediately close the mouth of the test tube with the cork containing the delivery tube. Hold a test tube with lime water at the other end of the delivery tube.
Observation: Dilute HCl reacts with sodium carbonate to release a colourless gas. The gas turns lime water milky.
(B) Properties of Sodium Hydroxide
Litmus Test
Experiment: Take two clean test tubes. Pour 1 mL of dilute NaOH into each test tube. Add a drop of blue litmus solution in one test tube and a drop of red litmus solution in the second test tube.
Observation: Blue litmus solution shows no change.
The red litmus solution changes to blue colour.Inference: Dil. NaOH shows a basic character.
Reaction with Zinc Metal
Experiment: Take a clean test tube. Add zinc metal granules/zinc powder into it. Pour 2 mL of NaOH solution into the tube. Hold the test tube with a test tube holder and heat it.
Bring a burning matchstick near the mouth of the test tube.Observation: On heating the mixture; the reaction begins, and colourless gas is evolved.
The burning matchstick burns with a ‘pop’ sound.Inference: Hydrogen gas always burns with a 'pop' sound.
Reaction with Solid Sodium Carbonate
Experiment: Take a clean test tube. Add 2 mL of NaOH solution in a tube and 1g of sodium carbonate. Heat the mixture.
Observation: No change.
Inference: Dil. NaOH does not react with sodium carbonate.
Precautions
(Only two precautions are to be written and I have chosen these)
Use clean test tubes.
Handle hydrochloric acid and sodium hydroxide solutions very carefully.
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