Mole Concept — Set 1
Chemistry · मोल संकल्पना · Questions 1–10 of 40
One mole is defined as the amount of substance that contains?
Correct Answer: D. 6.022 × 10^23 elementary entities
• **Avogadro’s number** = Exactly 6.022 × 10^23 particles define one mole of any substance. • **1 mole = 6.022 × 10^23** — Fixed by SI definition to count atoms, molecules, ions, etc. • 💡 Wrong-option analysis: A: 3 × 10^8 is speed-related magnitude; B: 9.8 is gravitational acceleration; C: 1.602 × 10^-19 is elementary charge in coulombs.
The value of Avogadro’s constant is approximately?
Correct Answer: B. 6.022 × 10^23 mol^-1
• **6.022 × 10^23 mol^-1** = Option B is correct because Avogadro’s constant is about 6. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: 6.022 × 10^24 mol^-1; C: 6.022 × 10^22 mol^-1; D: 6.022 × 10^20 mol^-1
At STP, the molar volume of an ideal gas is closest to?
Correct Answer: D. 22.4 L
• **22.4 L** = Option D is correct because 1 mole of an ideal gas occupies about 22. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: 11.2 L; B: 44.8 L; C: 1.0 L
The molar mass of carbon dioxide (CO2) is?
Correct Answer: D. 44 g/mol
• **44 g/mol** = Option D is correct because CO2 has molar mass 12 + 16 + 16 = 44 g/mol. • **44** — Option D is correct because CO2 has molar mass 12 + 16 + 16 = 44 g/mol • 💡 Wrong-option analysis: A: 40 g/mol; B: 28 g/mol; C: 32 g/mol
How many moles of water (H2O) are present in 9 g of water? (H=1, O=16)?
Correct Answer: B. 0.50 mol
• **0.50 mol** = Option B is correct because moles = mass/molar mass = 9/18 = 0. • **18** — Option B is correct because moles = mass/molar mass = 9/18 = 0 • 💡 Wrong-option analysis: A: 0.25 mol; C: 1.00 mol; D: 2.00 mol
How many molecules are present in 0.25 mol of oxygen gas (O2)?
Correct Answer: A. 1.5055 × 10^23
• **1.5055 × 10^23** = Option A is correct because molecules = moles × NA = 0. • (Contextual detail from explanation) • 💡 Wrong-option analysis: B: 3.011 × 10^23; C: 2.4088 × 10^24; D: 6.022 × 10^23
The empirical formula of a compound represents?
Correct Answer: D. The simplest whole-number ratio of atoms
• **The simplest whole-number ratio of atoms** = Option D is correct because empirical formula gives the simplest whole-number ratio of atoms. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: The structural arrangement of atoms; B: Total mass of one molecule; C: Actual number of atoms in one molecule
Which statement is correct about molecular formula and empirical formula?
Correct Answer: A. Molecular formula is a whole-number multiple of empirical formula
• **Molecular formula is a whole-number multiple of empirical formula** = Option A is correct because molecular formula = n × empirical formula. • (Contextual detail from explanation) • 💡 Wrong-option analysis: B: Molecular formula gives the simplest ratio only; C: Empirical formula is always a multiple of molecular formula; D: They are always identical for every compound
Avogadro’s law states that at constant temperature and pressure?
Correct Answer: B. Equal volumes of gases contain equal numbers of molecules
• **Equal volumes of gases contain equal numbers of molecules** = Option B is correct because equal volumes of gases at the same T and P have equal numbers of molecules. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: Mass is proportional to pressure only; C: Pressure is proportional to volume; D: Volume is inversely proportional to temperature
The molarity (M) of a solution is defined as?
Correct Answer: A. Moles of solute per liter of solution
• **Moles of solute per liter of solution** = Option A is correct because molarity is moles of solute divided by liters of solution. • (Contextual detail from explanation) • 💡 Wrong-option analysis: B: Moles of solute per kg of solvent; C: Grams of solute per liter of solvent; D: Mass of solute per 100 g of solution