Question 1: Define Relative Formula Mass (Mr) and explain its significance in chemistry.

Answer: Relative Formula Mass (Mr) is the sum of the atomic masses of all atoms in a molecule or compound's formula. It is important for calculating quantities in chemical reactions and preparing solutions.

Question 2: Why is it useful to know the relative formula mass of a compound in laboratory work?

Answer: Knowing the relative formula mass allows chemists to accurately measure and prepare specific amounts of substances for reactions and analyses.

Question 1: Calculate the relative formula mass of water (H₂O). Atomic masses: H = 1, O = 16.

Answer: Mr(H₂O) = (2 × 1) + 16 = 18

Question 2: Determine the relative formula mass of calcium carbonate (CaCO₃). Atomic masses: Ca = 40, C = 12, O = 16.

Answer: Mr(CaCO₃) = 40 + 12 + (3 × 16) = 100

Question 1: Describe a simple experimental method to determine the relative formula mass of a salt sample.

Answer: Weigh a known mass of the salt, dissolve it in a known volume of water, and calculate the amount in moles using the molar mass, which is equivalent to the relative formula mass.

Question 2: List two safety precautions to observe when handling chemicals used in experiments to determine Mr.

Answer: Wear appropriate personal protective equipment (gloves, goggles) and work in a well-ventilated area.

Question 1: A student weighs 5.0 g of sodium chloride (NaCl). The molar mass of NaCl is 58.5 g/mol. Calculate the number of moles of NaCl in the sample.

Answer: Number of moles = 5.0 ÷ 58.5 ≈ 0.0855 mol

Question 2: If the relative formula mass of a compound is known to be 150, and you have 3 moles of it, what is the mass of the sample in grams?

Answer: Mass = 150 × 3 = 450 g

Question 1: Explain how understanding relative formula mass is important in the manufacturing of medicines.

Answer: Knowing the relative formula mass allows pharmaceutical chemists to accurately calculate the amounts of each component needed to produce a precise dosage, ensuring efficacy and safety of medicines. It also helps in quality control and formulation design.

Question 2: In the context of environmental science, how can calculating the relative formula mass of pollutants assist in pollution control?

Answer: Calculating the relative formula mass of pollutants helps in understanding their molecular quantities in emissions, enabling better measurement, regulation, and development of removal techniques to reduce environmental impact.