Practical Based Questions Class 10 Science With Answers
In this article, CBSE Class 10 Science Practical Based Questions are sharing with you, which is important from the point of view of practical examination.
♦ CBSE Class 10 Science Practical Based Questions ♦
1. Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.
Answer. Raw Materials Required For the preparation of soap in the laboratory are :
- Vegetable oil
- Sodium Hydroxide
- Common salt
Test to determine the nature of the reaction mixture: When a red litmus paper is dipped in the reaction mixture, the paper changes its colour to blue. Hence, the reaction mixture of the saponification reaction is basic in nature.
2. On opening the soda water bottle the dissolved CO2 comes out, would the pH of the solution increase or decrease as the gas comes out? Give reason.
Answer. The pH of soda water increases. Because soda contains carbonic acid which is the weak one. When CO2 escape the carbonic acid’s strength weakens and therefore pH would increases.
3. A student is to conduct an experiment to show CO2 is released during respiration. List two precautions that he/she must take for obtaining correct observation.
Answer. Two precautions to be taken are:
(i) Germinating seeds (living) should be used.
(ii) The experiment set up must be air-tight.
4. A student dropped a few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? Write a balanced chemical equation for both the change observed?
Answer. When dilute HCl is added to marble which is calcium carbonate, it forms calcium chloride, water, and carbon dioxide. The chemical equation for the reaction is as follows:
CaCO3 + 2HCl → CaCl2 + H2O + CO2
Carbon dioxide gas turns lime water milky due to the formation of calcium carbonate.
The chemical equation showing the reaction between lime water and carbon dioxide is as follows:
Ca(OH)2 + CO2 → CaCO3 + H2O
5.Dry ammonia gas has no action on litmus paper but a solution of ammonia in water turns litmus paper color. Why?
Answer. A solution of ammonia in water produces OH– ions which make the solution basic and turn red litmus paper blue.
6. State the pH of distilled water and rainwater. Justify your answer with proper reasoning.
Answer. The pH of distilled water is 7 because it has no dissolved minerals. The pH of rainwater is slightly acidic less than 7 because it becomes a little acidic due to CO2 and SO2 molecules present in the atmosphere.
7. Write any two precautions while performing the pH experiment?
Answer. Wash the dropper with water after each use or use a new dropper for different samples. Keep the pH paper away from chemicals while doing the experiment.
8. Write any two precautions to study the reaction between Zn and HCl?
Answer. Acids should be handled carefully. Hydrogen gas evolved is highly
inflammable, so it should be handled carefully.
9. Hydrogen gas is neutral to litmus paper. Explain how?
Answer. It is neither acidic nor basic. It does not affect blue and red litmus.
10. What is the color of zinc metal? What happens to its color when zinc reacts with the hydrochloric acid?
Answer. Silverfish gray. When zinc reacts with HCl, the resulting solution becomes colorless (white) and zinc turns into black colored zinc chloride.
11. A student took solid quicklime in a china dish and added a small amount of water in it. State the type of sound produced in the reaction. Mention the type of reaction?
Answer. The hissing sound is produced as it is an exothermic reaction. Combination reaction.
12. Write two precautions that must be taken while studying the decomposition reaction, when the ferrous sulfate crystals are heated in a boiling tube?
Answer. Keep your nose away from the gas like SO2 which is suffocative. Use a tube holder to heat the test tube.
13.A student prepares aqueous solutions of the following salts:
Copper sulfate, ferrous sulfate, sodium sulfate, and barium chloride.
Write the color of each solution thus formed?
Answer. Copper sulfate (aq) – blue in color
Ferrous sulfate (aq) – pale green in color
Sodium sulfate (aq) – colorless
Barium chloride (aq) – white in color