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Class 11 Chemistry Chapter 1: Some Basic Concepts of Chemistry Assertion-reason questions with answers

2 assertion-reason questions on Some Basic Concepts of Chemistry, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern, JEE Main and NEET, which are set from the same 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.

Question 1
Assertion (A): The molality of a glucose solution stays the same when the solution is warmed. Reason (R): Molality is defined using the mass of the solvent, and mass does not change with temperature.
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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 is the reason for A: molality = moles of solute per kg of solvent, and neither moles nor mass change on warming.

Question 2
Assertion (A): A balanced chemical equation has the same number of atoms of each element on its two sides. Reason (R): An equation may be balanced by changing the subscripts in the formulas of the reactants and products.
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Answer: (c) A is true, but R is false.

A is true: by the law of conservation of mass atoms are neither created nor destroyed. R is false: subscripts are fixed by the formulas and are never changed; only the coefficients are adjusted.

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Chapter 2: Structure of Atom →