Atoms and Molecules — Flashcards
Punjab Board · Class 9 · Science
30 flashcards for Atoms and Molecules (Punjab Board Class 9 Science) to test yourself on key terms and facts. Sample: "What is the Law of Conservation.
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What is the Law of Conservation of Mass? State it clearly.
Answer
The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction. In other words, the total mass of reactants (starting substances) always equals the total …
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of acetic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium acetate. Verify the Law of Conservation of Mass
Answer
To verify the Law of Conservation of Mass, we compare total mass of reactants with total mass of products: Reactants: sodium carbonate (5.3 g) + acetic acid (6 g) = 11.3 g Products: carbon dioxide (…
What is the Law of Constant Proportions (Law of Definite Proportions)?
Answer
The Law of Constant Proportions states that in a chemical compound, the elements are always present in definite proportions by mass, regardless of the source or method of preparation. For example, in …
If hydrogen and oxygen combine in a mass ratio of 1:8 to form water, what mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer
Given: Mass ratio of H:O = 1:8 Mass of hydrogen = 3 g Using the ratio: If 1 g of hydrogen requires 8 g of oxygen, Then 3 g of hydrogen requires: (3 × 8) / 1 = 24 g of oxygen Therefore, 24 g of oxyge…
What is Dalton's Atomic Theory? List its main postulates.
Answer
Dalton's Atomic Theory consists of six main postulates: 1. All matter is made of tiny particles called atoms that participate in chemical reactions. 2. Atoms are indivisible particles that cannot be …
Which postulate of Dalton's atomic theory is the result of the Law of Conservation of Mass?
Answer
Postulate 2: 'Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.' This postulate directly explains the Law of Conservation of Mass. Since atoms cannot be cr…
Which postulate of Dalton's atomic theory explains the Law of Definite Proportions?
Answer
Postulate 6: 'The relative number and kinds of atoms are constant in a given compound.' Also supported by Postulate 5: 'Atoms combine in the ratio of small whole numbers to form compounds.' These po…
How big are atoms? Express atomic size in appropriate units.
Answer
Atoms are extremely small. Their size is measured in nanometers (nm): 1 nanometer = 1 × 10⁻⁹ m 1 m = 10⁹ nm Relative sizes of some particles: - Hydrogen atom: 10⁻¹⁰ m - Water molecule: 10⁻⁹ m (1 nm)…
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