To study the properties of acid (HCl) by its reaction with Litmus solution (Blue/Red), Zinc metal and Solid sodium carbonate
Aim
To study the properties of HCl by its reaction with:a. Litmus solution (Blue/Red)
b. Zinc metal
c. Solid sodium carbonate
Theory
Acids are compounds that contain hydrogen and which dissolve in water to produce hydrogen ions (H+). Ions are particles that have an electrical charge. The hydrogen ions give acids their special properties but they only exist in solution, so an acid only displays its properties when it is dissolved in water. For example, HCI + aq → 4H+ (aq) + Cl- (aq) The more H+ ions are in a solution, the more acidic it will be.
• HCl is an acid which turns blue litmus red
• HCl reacts with zinc metal to form zinc chloride and hydrogen
• HCl reacts with solid sodium carbonate to release CO2 gas
Na2CO3 (s) + 2HCl (aq) → 2NaCl
Chemicals Required
Hydrochloric acid, Litmus solution (Blue and Red), Zinc metal, Sodium carbonate, Sodium hydroxide,
Apparatus Required
Test tubes, Test tube stand, Bunsen Burner, Matchstick and Dropper
Procedure and Observations Table
| Sl. No. | Procedure | Observation | Inference |
| 1. | Test with Litmus Solution (a) A little amount of blue litmus solutions is taken in a test tube and few drops of HCl is added to it using a dropper. (b) A little amount of red litmus solutions is taken in a test tube and few drops of HCl is added to it using a dropper. |
(a) Blue litmus turns red. (b) No changes in the colour of red litmus. |
HCl is an acid having pH value below 7. |
| 2. | Reaction with Zn metal A clean and dry test tube is taken and zinc metal is added to it and placed it on test tube stand. Few drops of HCl is added on Zn pieces with the help of dropper. |
A gas is evolved which burns with popping sound when a matchstick is brought near the mouth of the test tube. | The gas evolved is hydrogen. Zn(s) + HCl(aq) → ZnCl2 + H2 |
| 3. | Reaction with Na2CO3 A small quantity of solid sodium carbonate is taken in a flask and distilled water is added into it. The flask is corked with a double bore cork and a thistle funnel is inserted into the flask. Then a beaker containing lime water near the flask is placed. Then one end of the delivery tube is inserted into the flask and the other end into the beaker. HCl is added into the flask through the thistle funnel and the change in colour of the lime water is observed. |
A gas is evolved which turns lime water milky. | The gas produced is carbon dioxide which gives brisk effervescence. Na2CO3(s) + 2HCl(aq) → 2NaCl + H2O + CO2 |
Discussions
1. Hydrochloric acid turns blue litmus paper to red and shows no effect with red litmus solution.
2. Hydrochloric acid gives hydrogen gas when a piece of zinc is dipped in it.
3. Hydrochloric acid gives carbon dioxide gas with sodium carbonate.
Precautions
1. Hydrochloric acid should be handled with care because it can bum skin and clothes.
2. Only small quantity of chemicals should be used.
3. Hands should be cleaned properly after completing the experiments.
4. All the observations should be noted carefully.
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