INTRODUCTION
In this experiment, we will learn to read the properties of acids and bases.
BASIC BUILDING CONCEPT
1. The taste of acid is sour, and the base taste is bitter.
2. The reaction of an acid with a metal evolves hydrogen gas and forms a salt.
3. The reaction of a base with metal evolves hydrogen gas and forms a negative ions salt consisting of metal and oxygen.
4. The reaction of an acid with metal carbonates gives out salt, carbon dioxide and water.
5. There is no reaction between a base and metal carbonates.
PROPERTIES OF ACIDS AND BASES
let us have a look at the following experiments to conclude the Properties of Acids and Bases
EXPERIMENT A: AIM
To determine the properties of acid, which is HCl, by their reaction with
1. Litmus solution(red/blue),
2. Zinc metal(Zn),
3. Sodium carbonate(Na2CO3).
MATERIAL REQUIRED
1. Test tubes,
2. Test tube stand,
3. Test tube holder,
4. Cork,
5. Dropper,
6. Beaker,
7. Red and blue litmus,
8. Zinc metal granules,
9. Solid sodium carbonate,
10. Dilute HCl.
THEORY
1. Hydrochloric acid, i.e., HCl, is an acid that can turn blue litmus to red and leave red litmus unchanged.
2. When HCl reacts with Zinc metal, zinc chloride is formed, and hydrogen is evolved,
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2 ↑(aq)
In the air, hydrogen gas burns with a pop sound.
H2(g) + O2(g) → 2H2O(l)
3. When HCl reacts with sodium carbonate, it forms carbon dioxide, which can turn lime water milky. When CO2 passes through a solution, its milkiness completely disappears.
Na2CO3(aq/s) + 2HCl (aq) → 2NaCl (aq) + H2O(l) + CO2(aq)
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
White precipitate (milky)
CaCO3(s) + H2O(l) + CO2(aq) → Ca(HCO3)2(aq)
Soluble (milkiness disappears)
PROCEDURE AND OBSERVATIONS
| S.NO | EXPERIMENT | OBSERVATION | INFERENCE |
|---|---|---|---|
| 1. | Litmus test Take two test tubes and add 1ml of HCl solution to each test tube. Mark them A and B. Place them on a test tube holder. In the test tube, A put red litmus and in test tube B, put blue litmus. Observe the colour change in both test tubes. | The blue colour of litmus turns into red colour and there is no change in red litmus. | HCl has an acidic character. |
| 2. | Reaction with zinc metal In a test tube, add zinc granules and dilute HCl. On the mouth of the test tube, put a cork with a fine jet. Bring a lighted matchstick near the mouth of the fine jet and observe it. | Hydrogen gas bubbles are formed. A pop sound is heard. | On reaction with zinc, dilute HCl forms hydrogen gas. |
| 3. | Na2CO3 test In a test tube, add sodium carbonate and dilute HCl. Pass the gas formed through lime water and observe the change. | A colourless and odourless gas will evolve. This gas will turn lime water milky. When passing the gas in lime water, the milkiness disappears. | CO2 gas is evolved in the reaction of H2O and Na2CO3. Na2CO3(aq/s) + 2HCl (aq) → 2NaCl (aq) + H2O(l) + CO2(aq) |
RESULT
1. HCl will turn blue litmus to red.
2. On reaction with zinc metal, HCl liberates hydrogen gas.
3. On reaction with sodium carbonate, HCl liberates carbon dioxide gas.
PRECAUTIONS
1. Hydrogen chloride is a strong acid and corrosive, so handle it with utmost care.
2. For burning hydrogen, a fine jet should be taken.
3. Be extra careful while performing this experiment.
4. To avoid a slow reaction, use clean zinc granules.
5. Wash your hands properly after the experiment.
EXPERIMENT B: AIM
To read the properties of bases (NaOH) by their reaction with the following substances.
1. Blue and red litmus paper,
2. Zinc metal (Zn),
3. Solid sodium carbonate(Na2CO3).
MATERIAL REQUIRED
1. Dilute NaOH,
2. Test tubes,
3. Test tube holder,
4. Test tube stand,
5. Red and blue litmus solutions,
6. Zinc metal,
7. Sodium carbonate
8. Droppers.
THEORY
1. The nature of NaOH (sodium hydroxide) is basic, and it turns the red colour of litmus to blue and leaves blue litmus unchanged.
2. When NaOH reacts with zinc metal, it forms sodium zincate, and hydrogen gas evolves.
Zn (s) + 2NaOH(aq) → Na2ZnO2(aq) + H2 ↑
3. There is no reaction occurs between Sodium hydroxide and sodium carbonate.
PROCEDURE AND OBSERVATION
| S.NO | EXPERIMENT | OBSERVATION | INFERENCE |
|---|---|---|---|
| 1. | Litmus paper Take two test tubes and add 1ml of NaOH solution to each test tube. Mark them A and B. Place them on a test tube holder. On the test tube, A put red litmus and on the test tube B, put blue litmus. Observe the colour change in both the tube | The red colour of litmus turns into blue colour and there is no change in blue litmus. | Sodium hydroxide has a basic nature. |
| 2. | Reaction with zinc metal In a test tube, add zinc granules and dilute NaOH. On the mouth of the test tube, put a cork with a fine jet. Bring a lighted matchstick near the mouth of the fine jet and observe it. | Hydrogen gas bubbles are formed. A pop sound is heard. | In reacting with Zn, NaOH forms hydrogen gas. |
| 3. | Na2CO3 test Take small amounts of sodium carbonate and sodium hydroxide in a test tube. | There will be no change occur. | Sodium hydroxide does not react with sodium carbonate. |
RESULT
1. NaOH turns blue litmus to red and leaves blue litmus unchanged.
2. NaOH releases hydrogen gas in reaction with zinc metal.
3. NaOH does not react with sodium carbonate.
PRECAUTIONS
1. NaOH is a strong base so handle it with utmost care.
2. Clean zinc granules should be used.
3. All chemicals should be used in small quantities.
4. For burning hydrogen, a fine jet should be taken.
5. Wash your hands after performing experiments.
VIVA QUESTIONS WITH ANSWERS
Q.1 What was the aim of our experiment?
ANS. To determine the properties of acids and bases by given substances.
Q.2 What is the chemical formula of Sodium carbonate?
ANS. Na2CO3.
Q.3 What is the effect of acid on litmus paper?
ANS. Acid turns blue litmus to red.
Q.4 Does acid change red litmus?
ANS. No
Q.5 What is the effect of a base on litmus paper?
ANS. The base turns red litmus to blue.
Q.6 Does base change blue litmus?
ANS. No
Q.7 What kind of metal displaces hydrogen from acid?
ANS. Those metals that are above hydrogen in a reactivity series are able to displace hydrogen from acid.
Q.8 What is the nature of milk of magnesia, acidic or basic?
ANS. Acidic
Q.9 Write the reaction between zinc and sodium hydroxide?
ANS. Zn (s) + 2NaOH(aq) → Na2ZnO2(aq) + H2 ↑
Q.10 Does sodium hydroxide reacts with sodium carbonate?
ANS. No
Saquib Siddiqui is a Mechanical Engineer and a content creator. He has special interest in science experiments and teaches the same to school and college students. He is also a technical lead at RUDE LABS PVT. LTD.
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