To study the properties of base (NaOH) by its reaction with Litmus solution (Blue/Red), Zinc metal and Solid sodium carbonate
Aim
To study the properties of NaOH by its reaction with:a. Litmus solution (Blue/Red)
b. Zinc metal
c. Solid sodium carbonate
Theory
Acids are compounds that contain hydroxyl group which dissolve in water to produce hydroxyl ions (OH-). Ions are particles that have an electrical charge.
For example, NaOH (aq) → Na+ (aq) + OH- (aq) The more OH- ions are in a solution, the more basic it will be.
• NaOH is a base which turns red litmus blue.
• NaOH reacts with zinc metal to form sodium zincate and hydrogen.
• NaOH doesn't react with solid sodium carbonate but form alkaline solution.
Chemicals Required
Sodium Hydroxide, Phenolphthalein, 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 red litmus solutions is taken in a test tube and few drops of NaOH is added to it using a dropper. (b) 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. |
(a) Red litmus turns blue. (b) No changes in the colour of blue litmus. |
NaOH is an alkali having pH value more than 7. |
| 2. | Reaction with Zn metal Some pieces of zinc metal in a boiling tube is taken. Few drops of NaOH is added into the boiling tube using a dropper. Then a dropper with a fine jet on the mouth of the tube is placed. The boiling tube is heated. A burning matchstick near the mouth of the fine jet is brought. |
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) + 2NaOH(aq) → Na2ZnO2 + H2 |
| 3. | Reaction with Na2CO3 A small quantity of solid sodium carbonate in a test tube is taken and a little amount of NaOH solution is added into it. The test tube is shaken well. Few drops of phenolphthalein is added into the test tube. |
The solution in the test tube turns pink. | Both NaOH and Na2CO3 are alkali so they do not react but form alkaline solution. Phenolphthalein gives pink colour in an alkaline medium. |
Discussions
1. Sodium Hydroxide turns red litmus paper to blue and shows no effect with blue litmus solution.
2. Sodium Hydroxide gives hydrogen gas when a piece of zinc is dipped in it.
3. Sodium Hydroxide does not react with solid sodium carbonate.
Precautions
1. Take small quantities of zinc, HCl and NaOH for their reaction, otherwise large amount of hydrogen produced may cause explosion.
2. For hydrogen burning take a fine jet.
3. Add HCl to Na2CO3, only when apparatus is made carefully airtight.
3. NaOH and HCl are injurious, handle these chemicals carefully.
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