#solutions

CHEMISTRY

What is the molality of a solution containing 8 g of NaOH in 400 g of water? (Molar mass of NaOH = 40 g/mol)

Given: What is the molality of a solution containing 8 g of NaOH in 400 g of water? (Molar mass of NaOH = 40 g/mol) These values define the system as per NCERT data. Formula: Moles = 8 / 40 = 0.2 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Mass of solvent = 0.4 kg. Molality = 0.2 / 0.4 = 0.5 m. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

What is the mass percentage of a solution formed by mixing 120 g of a 20% (w/w) solution with 180 g of a 10% (w/w) solut

Given: What is the mass percentage of a solution formed by mixing 120 g of a 20% (w/w) solution with 180 g of a 10% (w/w) solution? Formula: Mass of solute from first = 0.20 × 120 = 24 g. Substitution & Calculation: Mass of solute from second = 0.10 × 180 = 18 g . Total solute = 24 + 18 = 42 g. Total mass = 120 + 180 = 300 g. Mass % = 42/300 × 100 = 14% . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

A solution has a density of 1.22 g/mL and contains 35% by mass Hâ‚‚SOâ‚„. What is its molarity? (Molar mass of Hâ‚‚SOâ‚„

Given: A solution has a density of 1.22 g/mL and contains 35% by mass H₂SO₄. What is its molarity? (Molar mass of H₂SO₄ = 98 g/mol) These values define the system as per NCERT data. Formula: H₂SO₄ = 35 g. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Assume 100 g solution. . Moles = 35 / 98 ≈ 0.3571 mol. Volume = 100 / 1.22 ≈ 81.97 mL = 0.08197 L. Molarity = 0.3571 / 0.08197 ≈ 4.36 M ≈ 4.4 M. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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Water and Mole Concept

What is the percentage composition (w/v) of a 5g NaCl solution in 100mL of water?

5% accurately defines or describes the concept asked in this question. Within Water and Mole Concept, precise definitions and terminology are essential for clear scientific communication. The other options (0.5%, 10%, and 20%) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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