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#percent composition

3 public questions tagged with this topic.

CHEMISTRY

What is the mass percentage of a solution made by dissolving 30 g of sucrose in 120 g of water?

Given: What is the mass percentage of a solution made by dissolving 30 g of sucrose in 120 g of water? Formula: Total mass of solution = 30 g + 120 g = 150 g. Substitution & Calculation: Mass % = fracMass of sucroseTotal mass × 100 = 30/150 × 100 = 20% . 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

In the Dumas method, 0.5 g of a compound gave 134.4 mL of N₂ at STP. What is the percentage of nitrogen? (Atomic mass: N

Given: In the Dumas method, 0.5 g of a compound gave 134.4 mL of N₂ at STP. What is the percentage of nitrogen? (Atomic mass: N = 14) These values define the system as per NCERT data. Formula: Mass of N₂ = 28 × 134.4/22400 = 0.168 g. This is standard NCERT relation. Substitution & Calculation: Mass of N = 0.168 g. Percentage = 0.168 × 100/0.5 = 33.6% . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.

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

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CHEMISTRY

A compound contains 40% carbon and 60% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, O = 16)

Given: A compound contains 40% carbon and 60% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, O = 16) Formula: C = 40 g, O = 60 g. Substitution & Calculation: Assume 100 g. . Moles: C = 40 / 12 = 3.33, O = 60 / 16 = 3.75. Ratio: 3.33 / 3.33 : 3.75 / 3.33 ≈ 1 : 1.125. Multiply by 4: 4 : 5. Empirical formula = C₄O₅. 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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