Measurement of Matter — Maharashtra (SSC) Class 9 Science Solutions (Free)
Free step-by-step Maharashtra (SSC) Class 9 Science solutions for "Measurement of Matter" — important questions with detailed answers, download PDF for board exam preparation.
TL;DR: Free step-by-step Maharashtra (SSC) Class 9 Science solutions for "Measurement of Matter" — important questions with detailed answers, download PDF fo…
By Syllab.in · Updated
Q1: Define relative atomic mass and relative molecular mass.
Relative atomic mass (RAM): Mass of one atom of an element compared to 1/12 of mass of one ¹²C atom. It is a ratio, no units. Relative molecular mass (RMM): Sum of RAM of all atoms in a molecule. Example: H₂O = 2(1) + 16 = 18, so RMM of water is 18.
Q2: Calculate the number of moles in 44 g of CO₂ (C = 12, O = 16).
Step 1: Calculate molar mass of CO₂ = 12 + 2(16) = 12 + 32 = 44 g/mol
Step 2: Given mass = 44 g
Step 3: Number of moles = mass/molar mass = 44/44 = 1 mole
Number of moles = 1 mol
Q3: State the law of conservation of mass with an example.
Law of conservation of mass: Mass cannot be created or destroyed in a chemical reaction; total mass of reactants = total mass of products. Example: Burning 12 g of carbon in 32 g oxygen produces 44 g CO₂. (12 + 32 = 44). This applies to all chemical changes.
Q4: Define Avogadro's number and its value.
Avogadro's number (Nₐ) is the number of particles (atoms, molecules, ions, electrons) present in one mole of a substance. Value: Nₐ = 6.02 × 10²³ particles/mole. Example: 1 mole of H₂ contains 6.02 × 10²³ molecules of H₂.
Q5: Calculate the number of atoms in 4 g of helium (He = 4, Nₐ = 6.02 × 10²³).
Step 1: Molar mass of He = 4 g/mol
Step 2: Number of moles = mass/molar mass = 4/4 = 1 mole
Step 3: Number of atoms = moles × Nₐ = 1 × 6.02 × 10²³ = 6.02 × 10²³ atoms
Showing 5 of 7 questions — full solutions on the page.