10th Class Science Question | 10th Class Science Question with Answers

10th Class Science Question

Question 1.
Identify ‘x’, ‘y’ and ‘z’ in the following reaction :

(a) x = gas; y = reaction condition; z = gas
(b) x = solid; y = liquid; z = gas
(c) x = number of moles of KClO₃; y = reaction condition; z = number of molecules of oxygen
(d) x = physical state of KClO₃ and KCl;
y = reaction condition, z = physical state of O₂.
Answer:

Question 2.
Assertion (A) : Following is a balanced chemical equation for the action of steam on iron : 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Reason (R): The law of conservation of mass holds good for a chemical equation.
(a) Both (A) and (R) are true and reason (R) is the correct explanation of the assertion (A)
(b) Both (A) and (R) are true, but reason (R) is not the correct explanation of the assertion (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
A balanced chemical equation must obey the law of conservation of mass.

Question 3.
(a) State the law that is followed by balancing a chemical equation.
(b) Balance the following chemical equation: Na + H₃O → NaOH + H₂ 
Answer:
(a) Law of conservation of mass is followed for balancing a chemical equation which states that mass can neither be created nor destroyed in a chemical reaction. That is, the total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants in a balanced equation.

(b) 2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

Question 4.
Explain the significance of photosynthesis.
Write the balanced chemical equation involved in the process.
Answer:
Photosynthesis means synthesis with the help of light. It is the process that gives life to all living beings.
Photosynthesis is a process by which plants utilize carbon dioxide and water in the presence of sunlight to produce glucose and oxygen.

Question 5.
Write balanced chemical equations for the following chemical reactions:
(a) Hydrogen + Chlorine → Hydrogen chloride
(b) Lead + Copper chloride → Lead chloride + Copper
(c) Zinc oxide + Carbon → Zinc + Carbon monoxide
Answer:
(a) H_2(g) + Cl_2(g) → 2HCl_(g)
(b) Pb_(s) + CuCl_2(aq) → PbCl_2(aq)+ Cu_(s)
(c) ZnO_(s) + C_(s) → Zn_(s) + CO_(g)

Question 6.
Calcium oxide reacts vigorously with water to produce slaked lime.
CaO_(s) + H₂O_(l) → Ca(OH)_2(aq)
This reaction can be classified as
(A) Combination reaction
(B) Exothermic reaction
(C) Endothermic reaction
(D) Oxidation reaction
Which of the following is a correct option?
(a) (A) and (C)
(b) (C) and (D)
(c) (A), (C) and (D)
(d) (A) and (B)
Answer:
(d) The reaction between CaO and H₂O to form Ca(OH)₂ is an exothermic combination reaction.

Question 7.
When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution.
(a) combination reaction
(b) displacement reaction
(c) decomposition reaction
(d) double displacement reaction.
Answer:
(d) CuSO₄ + H₂S → CuS + H₂SO₄
It is a double displacement reaction as in this reaction CuSO₄ and H₂S reacting by exchange of Cu²⁺ and H⁺ ions to from two new compounds i.e., CuS and H₂SO₄.

Question 8.
In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution :
(A) exchange of atoms takes place
(B) exchange of ions takes place
(C) a precipitate is produced
(D) an insoluble salt is produced
The correct option is (2020)
(a) (B) and (D)
(b) (A) and (C)
(c) only (B)
(d) (B), (C) and (D)
Answer:
(d) In this reaction exchange of Na⁺ and Ba²⁺ ions takes place forming BaSO₄ which is a white precipitate i.e., an insoluble salt.
Na₂SO₄ + BaCl₂ → BaSO₄ ↓+ 2NaCl

Question 9.
In which of the following, the identity of initial substance remains unchanged?
(a) Curdling of milk
(b) Formation of crystals by process of crystallisation
(c) Fermentation of grapes
(d) Digestion of food
Answer:
(b): Formation of crystals is a physical change rest others are chemical change.

Question 10.
Study the following equation of a chemical reaction
H₂ + Cl₂ → 2HCl
(i) Identify the type of reaction.
(ii) Write a balanced chemical equation of another example of this type of reaction.
Answer:
(i) Combination reaction.
(ii) Another example of combination reaction is

Question 11.
With the help of an example explain what happens when a base reacts with a non- metallic oxide. What do you infer about the nature of non-metal oxide?
Answer:
Oxides of non-metals react with bases to form salt and water. For example, the reaction between carbon dioxide and calcium hydroxide. Calcium hydroxide, which is a base, reacts with carbon dioxide to produce salt and water.

Hence, oxides of non-metals are acidic in nature.

Question 12.
What is observed when carbon dioxide gas is passed through lime water
(i) for a short duration?
(ii) for a long duration? Also write the chemical equations for the reactions involved.
Answer:
(i) When CO₂ is passed through lime water for short interval of time, it turns milky due to the formation of insoluble calcium carbonate.

(ii) If CO₂ is passed for long duration through lime water, the white precipitate formed dissolves due to the formation of soluble calcium hydrogen carbonate and the solution becomes clear.

Question 13.
2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the content are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.
Answer:
It is observed that active metals like zinc react with strong bases like NaOH, KOH etc. to liberate hydrogen gas and corresponding salt.

The evolution of gas is confirmed by the bubble formation in soap solution.
Test to detect H₂ gas: When burning matchstick is kept on the mouth of this test tube, pop sound is heard which confirms the presence of H₂ gas. When Zn metal reacts with dilute solution of strong acid, H₂ gas is evolved.

Question 14.
Write the names of the product formed when zinc reacts with NaOH. Also write the balanced chemical equation for the reaction involved. Write a test to confirm the presence of the gas evolved during this reaction.
Answer:
Refer to answer 3.

Question 15.
To. a solution of sodium hydroxide in a test tube, two drops of phenolphthalein are added.
(i) State the colour change observed.
(ii) If dil HCl is added dropwise to the solution, what will be the colour change?
(iii) On adding few drops of NaOH solution to the above mixture the colour of the solution reappears. Why?
Answer:
(i) On adding phenolphthalein to NaOH solution, the colour becomes pink.
(ii) On adding dilute HCl solution dropwise to the same test tube, the pink colour disappears and the solution again becomes colourless.
(iii) On again adding NaOH to the above mixture, pink colour reappears because the medium becomes basic again.

Question 16.
Most of the digestion and absorption of the food takes place in the
(a) small intestine
(b) liver
(c) stomach
(d) large intestine.
Answer:
(a) small intestine

Question 17.
Mention the raw materials required for photosynthesis.
Answer:
Raw materials required for photosynthesis are carbon dioxide (CO₂), water, light and chloroplast.

Question 18.
State the location and function of gastric glands.
Answer:
Gastrifc glands are present in the wall of the stomach. They secrete gastric juices containing mucus, protein digesting enzymes pepsin, rennin and hydrochloric acid (HCl).

Question 19.
Name the glands present in the wall of the stomach that release secretions for digestion of food. Write the three components of secretion that are released by these glands.
Answer:
Stomach’s muscular wall contains gastric glands. These glands secrete gastric juices which contain dilute hydrochloric acid, mucus and two protein digesting enzymes rennin and pepsin.

Question 20.
Complete the following flow chart as per the given instructions.

Answer:

a – Hydrochloric acid (HCl)
b – Protein digesting enzyme pepsin
c – Mucus
d – HCl makes medium acidic for the activation of an enzyme pepsin.
e – Pepsin acts in acidic medium which breaks down proteins into peptones.
f – Mucus protects the inner lining of stomach from corroding action of HCl.