Question 1: Define the principle of conservation of mass in chemical reactions.

Answer: The principle that mass remains constant in a chemical reaction; the total mass of reactants equals the total mass of products.

Question 2: Explain why the total mass of reactants and products is the same in a closed system.

Answer: Because no mass is lost or gained during the reaction; atoms are simply rearranged, maintaining the total mass.

Question 1: A reaction involves 10 g of magnesium reacting with 20 g of sulphur. What is the total mass of the products? (Assuming no mass is lost)

Answer: 30 g

Question 2: Calculate the number of moles of aluminium (Al) in 54 g. (Atomic mass of Al = 27 g/mol)

Answer: 2 mol

Question 3: If 5 moles of hydrogen gas (H₂) react with excess oxygen, what is the mass of water (H₂O) produced? (Molecular mass of H₂O = 18 g/mol)

Answer: 90 g

Question 1: Describe a simple experiment to demonstrate the conservation of mass during a chemical reaction. Include the variables involved and safety precautions.

Answer: Students can measure the mass of reactants in a sealed container before and after a reaction such as magnesium reacting with hydrochloric acid. Variables include temperature, pressure, and container integrity. Safety precautions include wearing goggles, gloves, and ensuring the container is properly sealed to prevent leaks of corrosive gases.

Question 2: In an experiment, 12.0 g of calcium carbonate decomposes to produce 4.8 g of calcium oxide and 7.2 g of carbon dioxide. Explain how this supports the principle of conservation of mass.

Answer: The total mass of the products (4.8 g + 7.2 g = 12.0 g) equals the initial mass of calcium carbonate, demonstrating mass conservation in the reaction.

Question 1: A sealed flask contains 25 g of a reactant mixture. After a reaction, the total mass remains 25 g, but the gases evolved are not captured. Explain why the mass remains the same and how this relates to the conservation of mass.

Answer: Because gases escape into the environment, but in a sealed system, no mass is lost or gained; the total mass remains constant, illustrating the principle of conservation of mass.

Question 1: Explain why balancing chemical equations is important in demonstrating the conservation of mass.

Answer: Balancing chemical equations ensures that the number of atoms for each element is the same on both sides, reflecting the conservation of mass and ensuring the reaction accurately represents real transformations.

Question 2: Which industry relies heavily on the principle of conservation of mass when producing chemicals, and why?

Answer: Petrochemical industry