Question 1: Define a mole in the context of chemistry and explain its importance when measuring substances.

Answer: A mole is a unit that measures the amount of a substance, representing 6.022 x 10^23 particles (atoms, molecules, ions). It allows chemists to count particles by weighing them.

Question 2: Which of the following is equivalent to 2 moles of a substance? A) 2 particles B) 2 grams C) 1.2044 x 10^24 particles D) 2 molecules

Answer: C) 1.2044 x 10^24 particles

Question 3: Fill in the blank: One mole of any substance contains __________ particles.

Answer: 6.022 x 10^23

Question 4: Describe the difference between a mole and a gram.

Answer: A mole is a counting unit representing a specific number of particles, whereas a gram is a unit of mass. The mass of one mole depends on the substance’s molar mass.

Question 5: What is the molar mass of water (H₂O)? Show your working.

Answer: Molar mass of H₂O = (2 x 1.008 g/mol) + (16.00 g/mol) = 18.016 g/mol

Question 6: Calculate the number of grams in 3 moles of carbon dioxide (CO₂). (Molar mass of CO₂ = 44.01 g/mol)

Answer: Mass = moles x molar mass = 3 mol x 44.01 g/mol = 132.03 grams

Question 7: A sample contains 2.5 x 10^24 particles of sulfur. How many moles does this sample contain?

Answer: Moles = particles / (6.022 x 10^23) = 2.5 x 10^24 / 6.022 x 10^23 ≈ 4.15 mol

Question 8: Explain why understanding moles is essential in chemical reactions.

Answer: Understanding moles allows chemists to relate quantities of different substances in a reaction, ensuring the correct proportions are used for reactions to proceed efficiently and predictably. It bridges the gap between atomic scale and laboratory measurements.

Question 9: In an experiment, 5 grams of aluminum react with oxygen. The molar mass of aluminum is 26.98 g/mol. How many moles of aluminum are used?

Answer: Moles = 5 g / 26.98 g/mol ≈ 0.185 mol

Question 10: Identify at least two safety precautions to consider when measuring and handling chemicals involved in molar calculations.

Answer: Wear protective gloves and safety goggles to prevent chemical burns or splashes. Work in a well-ventilated area to avoid inhaling fumes.

Question 11: A factory produces 1000 kg of sulfuric acid annually. If the molar mass of sulfuric acid (H₂SO₄) is 98.08 g/mol, approximately how many moles are produced each year?

Answer: Mass in grams = 1,000,000 g; Moles = 1,000,000 g / 98.08 g/mol ≈ 10,204 mol