Class 10 Record Experiment 1

 To study the properties of acids and bases (dilute HCl and dilute NaOH) by their reaction with

Aim
To study the properties of acids and bases (dilute HCl and dilute NaOH) by their reaction with
(a) Litmus solution (Blue/Red) (b) Zinc metal (c) Solid sodium carbonate

Theory
Hydrochloric acid
> Chemical formula of hydrochloric acid is HCl.
> When it is dissolved in water; releases H+(aq) ions, these H+ ions cannot exist alone. Hence, it combines with water to form H3O+ (aq) ions.

> The acidic property is seen due to this H+(aq) ions/H3O+ ions.

Properties of hydrochloric acid

> It turns blue litmus solution red.
> Hydrochloric acid reacts with metals to release hydrogen gas.

> Test for H2 gas: When a burning splinter is brought near the mouth of test tube releasing H2 gas, it bums with a ‘pop sound’.
> Hydrochloric acid react with sodium carbonate to release CO2 gas.

> Test for CO2 gas: When CO2 gas is allowed to pass through freshly prepared lime water, then the lime water turns milky or when a burning splinter is brought near the mouth of the test tube releasing CO2 gas then the burning splinter extinguishes.
Sodium hydroxide
> Chemical formula of sodium hydroxide is NaOH.
> When it is dissolved in water releases OH– ions.

Properties of Sodium hydroxide
> It turns red litmus solution blue.
> Not all bases react with zinc metal to release H2 gas but sodium hydroxide solution reacts with zinc metal to release hydrogen gas.

> Sodium hydroxide do not react with solid sodium carbonate.

Materials Required
A test tube stand, test tubes, match box, 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.

Procedure
(A) Properties of Hydrochloric Acid

Experiment		Observation	Inference
1.	Litmus Test Take two clean test tubes. Pour 1 mL of dilute HCl solution in each test tube. Pour a drop of blue litmus in one test tube and a drop of red litmus solution in the second test tube.	Blue litmus solution turns red in first test tube. Red litmus solution shows no change in second test tube.	Dil. HCl shows acidic character.
2.	Reaction with Zinc Metal 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.	Zinc metal reacts with the acid. Test tube becomes warm and pressure is exerted on thumb due to release of a gas. The matchstick bums with a pop sound.	Zinc + dil. HCl → Zinc chloride + Hydrogen gas Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) Hydrogen gas always bums with a pop sound when lighted matchstick is introduced in it.
3.	Reaction with Sodium Carbonat Take a clean test tube. Add 2 mL of dilute HCl. Now add lg/pinch of sodium carbonate in it. Immediately close the mouth with cork containing delivery tube. Hold a test tube with lime water at the other end of the delivery tube.	Dilute HCl reacts with sodium carbonate to release a colourless gas. The gas turns lime water milky.	(i) Na2CO3 + 2HCl → 2NaCl + H20 + CO2 (ii)Ca(OH)2+CO2 → Lime waterCaCO3 +H2O White insoluble ppt

(B) Properties of Sodium Hydroxide

Experiment		Observation	Inference
1.	Litmus Test Take two clean test tubes. Pour 1 mL of dilute NaOH in 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.	Blue litmus solution shows no change. Red litmus solution changes to blue colour.	Dil. NaOH shows basic character.
2.	Reaction with Zinc Metal Take a clean test tube. Add zinc metal granules/zinc powder in it. Pour 2 mL of NaOH solution in 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.	On heating the mixture; reaction begins, colourless gas is evolved. The burning matchstick bums with a ‘pop’ sound.	Zn(s) + 2NaOH(aq) Na2ZnO2(aq) + H2(g) Hydrogen gas always bums with a pop sound.
3.	Reaction with Solid Sodium Carbonate Take a clean test tube. Add 2 mL of NaOH solution in a tube and 1 g of sodium carbonate. Heat the mixture.	No change.	Dil. NaOH doesn’t react with sodium carbonate.

Precaution

1. Use clean test tubes.

2. Use very small amount of chemicals.

3. Handle hydrochloric acid and sodium hydroxide solutions very carefully.

4. Shake the solutions and reaction mixtures carefully without spilling.

5. Always carry out the test for hydrogen with a very small volume of gas.

6. For H2 gas test, be careful as H2 catches fire. The flame on test tube can be seen due to H2 gas.

For lime water test, allow the CO2 gas to pass through lime water and shake the test tube by placing thumb on the mouth of the tube to get quick result.