AIM:

Studying the properties of acids (HCl) by their reaction with

(i) Litmus solution (Blue/Red)

(ii) Zinc metal (Zn)

(iii) Solid sodium carbonate (Na₂CO₃)

MATERIALS REQUIRED

Apparatus Required: Test tubes, test tube stand, test tube holder, cork, droppers, beaker, litmus (red and blue), Zn metal granules.

Chemical Required: Solid sodium carbonate, dil. HCL.

THEORY

1. Acids turn blue litmus red and do not affect red litmus. As HCl is an acid, it will turn blue litmus solution red.

2. HCl reacts with zinc metal, to forms a salt, zinc chloride (ZnCl₂) and hydrogen gas (H₂) is liberated.

3. Hydrogen gas burns in air with a pop sound.

4. HCL reacts with sodium carbonate (aqueous/solid) to liberate carbon dioxide (CO₂) which turns lime water milky. When an excess of CO₂ is passed through the solution, the milkiness disappears.

PROCEDURE

1.Litmus test

Take 1 ml dil. HCl in two test tubes each. Mark them ‘A’ and ‘B’ and put them in a test tube stand. Add blue litmus in a test tube ‘A’ and red litmus in a test tube ‘B’ Observe the colour change in both.
2. Reaction with Zn metal

Take a test tube and add zinc granules to it. Add to it dil. HCl. Place a cork with a fine jet on the mouth of the test tube. Bring a lighted matchstick near the mouth of the fine jet after some time and observe.

3. Na₂CO₃ test

Take a small amount of sodium carbonate in a test tube and add dil. HCL dropwise.

Pass the gas evolved through lime water and observe changes.

4. Note the observation in the observation table.

OBSERVATION TABLE

S.No.	Observation	Inference
1.	Blue litmus turns red. No change in the colour of red litmus.	HCL has acidic character.
2.	Bubbles of hydrogen gas are formed. A pop sound is obtained.	Zn reacts with dil. HCl liberates hydrogen gas.
3.	A colourless, odourless gas is evolved. The evolved gas turns lime water milky. On passing the gas in excess of lime water, the milkiness disappears.	CO2 gas is liberated on the reaction between dil. HCL and Na2CO3 2HCL + Na2CO3→ 2NaCl + CO2 + H2O

RESULT

1. HCI being acid turns blue litmus red.

2. It releases H₂ gas on reaction with Zn metal.

3. It liberates CO₂ gas on reaction with Na₂CO₃.

PRECAUTIONS

1. HCI is corrosive in nature, therefore, handle it with care.

2. Use small quantities of the chemical compounds.

3. Use zinc granules, otherwise, the reaction will occur very slowly.