Class 10 Science Answer Key 2025 Code 31/3/1
Hello Students,
Your Science paper for class 10 held today on 20.02.2025. Hope you did well in the exam. Here on cbsestudent.com, we are now providing you CBSE Class 10 Science Answer Key 2025 immediately after the exam. These are Answer Key of Science Paper Code 31/3/1 Set-1.
Though, these answer keys are unofficial as they have been prepared by the expert of the subject just after the exam, due care has been taken care.
Some of the important answer keys have brief explanation so that students can learn about the reasoning behind the right answer.
They will certainly give you a chance to estimates your marks in this paper. Answer Keys have focused on Multiple Choice Question (MCQs) appeared in the question paper.
Q.1 Consider the following chemical equation:
p Al + q H2O → r Al2O3 + s H2
To balance this chemical equation, the values of p, q, r and s must be respectively:
Answer: Option (C) is correct option – 2,3,1,3
Brief Explanation: It must to be ensured that number of atoms of each element is same on both the left and right sides of the equation. When we balance the equation on this principal, Option (C) is the most appropriate answer.
Q.2 Which of the given option represents a family of salts?
Answer: Option (B)- K2 SO4, Na2SO4, CaSO4
Brief Explanation: They belong to sulfate family of salts.
Q.3 The most common method of extraction of metals from their oxide ores is:
Answer: Option (A) – Reduction with carbon
Brief Explanation: Many metals exist in nature as oxide ores. These ores are chemically reduced to obtain pure metal. Carbon is a good reducing agent. So, it is commonly used to extract metals from their oxide ores.
Q.4 Given below are the structures of some of the hydrocarbons. Select the two structures which are related to each other from the given option:
Answer: Option (C) – (ii) and (iii)
Q.5 Choose the incorrect statement about the common reaction used in hydrogenation of vegetable oils
Answer: Option (D) – It is an addition reaction which occurs in the presence of an acid catalyst.
Brief Explanation: It is an addition reaction using a nickel or palladium catalyst. It converts liquid vegetable oil to solid or semi solid fats
Q.6 Match Column-I and Column-II and select the correct option from the choices provided.
Answer: Option (D) – a-iii, b-ii, c-i, d-iv
a.Site of fertilization of egg with the sperm – iii. Oviduct.
b.Site of implantation of embryo – ii. Uterus
c.Site of entry of sperm into the female reproductive tract – i. Vagina
d.Site through which the waste materials generated by the developing embryo are removed – iv. Placenta
Q.7 The part of the brain which maintains the posture and balance of the body is:
Answer: Option (C) – Cerebellum
Q.8 The plant hormone present in greater concentration in the areas of rapidly dividing cells is:
Answer: Option (B) – Cytokinins
Brief Explanation: Cytokinins promote cell division. So, they are found in greater concentrations in areas of rapid cell division.
Q.9 Select a pair of bisexual flowers from the following:
Answer: Option (B) – Hibiscus and mustard
Brief Explanation: These flowers contain both male (stamens) and female (pistils) reproductive organs.
Q.10 The gastric glands present in the wall of the stomach release:
Answer: Option (C) – Mucus and Pepsin
Q.11 Absolute refractive index of water and glass is 4/3 and 3/2 respectively. If the speed of light in glass is 2 x 108 m/s, the speed of light in water is:
Answer: Option (A) – 9/4 m/s
Q.12 When a beam of white light passes through a region of very fine dust particles, the colour of light that scatters the most in that region is:
Answer: Option (C) – Blue
Brief Explanation: Blue colour is of shorter wavelengths and shorter wavelengths scatter more than longer wavelengths like red colour.
Q.13 A wire of length ‘l’ is gradually stretched so that its length increases to 3l. If its original resistance is R, then its new resistance will be:
Answer: Option (C) – 9R
Q.14 Which one of the following statements is not true about a bar magnet?
Answer: Option (D) – The direction of magnetic field lines inside a bar magnet is from its north pole to its south pole.
Q.15 The strength of magnetic field produced inside a long straight current carrying solenoid does not depend upon:
Answer: Option (B) – Direction of current flowing through the solenoid.
Q.16 Other than the abiotic components which of the given biotic components are not required to make an aquarium with small herbivorous fishes a self sustaining system.
Answer: Option (D) – ii and iv
Terrestrial plants and terrestrial animals
Consumers as clown fishes and sea urchins
Q.17 Assertion (A): Hydrogen gas is not evolved when a metal reacts with nitric acid.
Reason (R): Nitric acid is a strong reducing agent and reduces the hydrogen produced in the reaction to water.
Answer: Option (C) – Assertion is true and Reason is false.
Brief Explanation: Nitric Acid is strong oxidizing agent, not a reducing agent.
Q.18 Assertion (A): In our actions of writing or talking, our nervous system communicates with muscles
Reason (R): Cranial nerves and spinal nerves form the peripheral nervous system.
Answer: Option (B) – Both Assertion and Reason are true and Reason is not the correct explanation of Assertion.
Q.19 Assertion (A): Magnetic field lines around a bar magnet never intersect each other.
Reason (R): Magnetic field produced by a bar magnet is a quantity that has both magnitude and direction.
Answer: Option (A) – Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
Q.20 Assertion (A): Use of jute bags for shopping reduces pollution.
Reason (R): Jute is biodegradable and its bag may be reused as and when needed.
Answer: Option (A) – Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
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