Class 10 Science Chapter 1: Chemical Reactions and Equations Assertion-reason questions with answers
2 assertion-reason questions on Chemical Reactions and Equations, each with its answer and the reason, written from the NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.
Both are true, and R explains A: Ca(OH)₂ + CO₂ → CaCO₃ (milky); with excess CO₂ the CaCO₃ becomes soluble calcium hydrogen carbonate, so the solution clears.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.
C + O₂ → CO₂: two substances form a single product, which makes it combination. That it gives out heat is true (it is exothermic) but is not what makes it a combination reaction.