Mole Concept and Avogadro's NumberPractice Questions & MCQs
Practice Mole Concept and Avogadro's Number questions from Atoms and Molecules (Class 9 Science) - important MCQs with answers and step-by-step solutions. Solve the sample questions below, then practice the full set free on the RankByte app.
Mole Concept and Avogadro's NumberQuiz - Solve & Score
Q1. A lab assistant weighs out 180 g of water on a digital balance for an experiment. How many moles of the substance does this sample contain?
- A.180 mol
- B.10 mol
- C.3240 mol
- D.0.1 mol
Answer: B. 10 mol
Molar mass of water = 18 g/mol. Moles n = mass / molar mass = 180 / 18 = 10 mol.
Q2. On opening a freshly sealed bottle, A research scholar finds it holds 440 g of carbon dioxide. How many moles are present in the bottle?
- A.440 mol
- B.19360 mol
- C.10 mol
- D.0.1 mol
Answer: C. 10 mol
Molar mass of carbon dioxide = 44 g/mol. Moles n = mass / molar mass = 440 / 44 = 10 mol.
Q3. A pharmacist carefully transfers 48 g of oxygen gas into a clean beaker before starting a reaction. The transferred amount corresponds to how many moles?
- A.1536 mol
- B.0.6667 mol
- C.1.5 mol
- D.48 mol
Answer: C. 1.5 mol
Molar mass of oxygen gas = 32 g/mol. Moles n = mass / molar mass = 48 / 32 = 1.5 mol.
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