Class 10 Science — CBSE Board Sample Paper

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Class 10 Science — CBSE Board Sample Paper — solved practice questions

8 Class 10 Board Sample Papers (CBSE) questions with step-by-step solutions. Attempt each, then reveal the answer.

1. Q1medium

   Identify 'p', 'q' and 'r' in the following balanced reaction: p Pb(NO3)2(s) --Heat--> q PbO(s) + r NO2(g) + O2(g)

   • A2,2,4
   • B2,4,2
   • C2,4,4
   • D4,2,2
   Show answer & solution

   Correct answer: (A) 2,2,4

   Balancing the thermal decomposition of lead nitrate: 2 Pb(NO3)2 -> 2 PbO + 4 NO2 + O2, so p=2, q=2, r=4.

2. Q2medium

   Match column I with column II and select the correct option using the given codes. Column I: a) A metal that forms amphoteric oxides b) A metal which melts when kept on our palm c) A metal that reacts with nitric acid d) A metal which cannot displace hydrogen from acids ; Column II: (i) Ga (ii) Au (iii) Al (iv) Mn

   • Aa - (ii), b - (i), c - (iii), d - (iv)
   • Ba - (iii), b - (i), c - (iv), d - (ii)
   • Ca - (iv), b - (ii), c - (iii), d - (i)
   • Da - (iii), b - (ii), c - (i), d - (iv)
   Show answer & solution

   Correct answer: (B) a - (iii), b - (i), c - (iv), d - (ii)

   Aluminium (Al) forms amphoteric oxides, gallium (Ga) melts on the palm due to its low melting point, manganese (Mn) reacts with nitric acid to evolve hydrogen, and gold (Au) cannot displace hydrogen from acids as it is below hydrogen in the reactivity series.

3. Q3easy

   Which among the following is considered as the strongest electrolyte?

   • ADilute acid
   • BDilute sugar solution
   • CGlucose solution
   • DEthanol in water
   Show answer & solution

   Correct answer: (A) Dilute acid

   A dilute acid ionises to release ions (H+ and anions) that conduct electricity, whereas sugar, glucose and ethanol solutions are non-electrolytes, so the dilute acid is the strongest electrolyte.

4. Q4medium

   An aqueous solution 'A' turns the phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. Which of the following statement is true for the solutions 'A' and 'B'?

   • AA is strongly basic and B is a weak base.
   • BA is strongly acidic and B is a weak acid.
   • CA has a pH greater than 7 and B has a pH less than 7.
   • DA has a pH less than 7 and B has a pH greater than 7.
   Show answer & solution

   Correct answer: (C) A has a pH greater than 7 and B has a pH less than 7.

   Phenolphthalein turns pink in a base, so A is basic (pH greater than 7). The pink colour disappears when neutralised by an acid, so B is acidic (pH less than 7).

5. Q5easy

   When 50g of lead powder is added to 300 ml of blue copper sulphate solution, after a few hours, the solution becomes colourless. This is an example of

   • ACombination reaction
   • BDecomposition reaction
   • CDisplacement reaction
   • DDouble displacement reaction
   Show answer & solution

   Correct answer: (C) Displacement reaction

   Lead is more reactive than copper, so it displaces copper from copper sulphate solution, decolourising it; this is a displacement reaction.

6. Q6medium

   The electronic configuration of three elements X, Y and Z are X- 2, 8, 7; Y- 2, 8, 2; and Z - 2, 8

   • AY and Z are metals
   • BY and X are non-metals
   • CX is a non-metal and Y is a metal
   • DY is a non-metal and Z is a metal
   Show answer & solution

   Correct answer: (C) X is a non-metal and Y is a metal

   X has 7 valence electrons and tends to gain electrons, so it is a non-metal; Y has 2 valence electrons and tends to lose them, so it is a metal (Z with a stable octet is a noble gas).

7. Q7easy

   Which of the following is an endothermic reaction?

   • ABurning of candle.
   • BCooking of food.
   • CDecomposition of Vegetable matter.
   • DReaction of Sodium with air
   Show answer & solution

   Correct answer: (B) Cooking of food.

   Cooking of food requires absorption of heat energy, making it an endothermic process, whereas the other options release energy.

8. Q8hard

   During cellular oxidation of Glucose, ATP is produced along with formation of other products in this reaction. Which of the following events is associated with production of maximum ATP molecules per molecule of Glucose during this process? Synthesis of

   • Aethanol in yeast
   • Blactic acid in muscle cells
   • Ccarbon dioxide in yeast cells
   • Dcarbon dioxide in human cells
   Show answer & solution

   Correct answer: (D) carbon dioxide in human cells

   Aerobic respiration in human cells breaks glucose completely into carbon dioxide and water, releasing the maximum amount of ATP compared to anaerobic pathways producing ethanol or lactic acid.

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