This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here's an explanation of the concepts and calculations from the image. The "Worked Example 2.2" illustrates how to determine the relative mass of an unknown substance using a beam balance, comparing it to a carbon-12 sample. Worked Example 2.2 Explanation: The example uses an analogy with beads. a)* A carbon-12 sample is represented by 12 beads. By definition, carbon-12 has a relative atomic mass of 12. This implies that each carbon-12 bead in this analogy has a relative mass of 1 unit. b)* An unknown sample is represented by x beads. c)* To find the relative mass of the unknown sample, the example assumes that x beads of the unknown sample have the same total mass as the 12 carbon-12 beads when balanced. Therefore, the total relative mass of the x unknown beads is 12 units. The formula A = (12)/(Number of beads in unknown sample) = (12)/(x) = y calculates the relative mass per bead of the unknown sample. So, y represents the relative mass of one bead of the unknown substance. Activity 2.2: Understanding relative molecular mass Relative molecular mass (M_r) is the sum of the relative atomic masses (A_r) of all the atoms in a molecule. We will use the approximate relative atomic masses: Hydrogen (H) ≈ 1.0, Carbon (C) ≈ 12.0, and Oxygen (O) ≈ 16.0. 1) For Water (H_2O): Step 1: Identify the atoms and their quantities. The molecule H_2O contains 2 hydrogen atoms and 1 oxygen atom. Step 2: List the relative atomic masses. A_r(H) = 1.0 A_r(O) = 16.0 Step 3: Calculate the relative molecular mass. M_r(H_2O) = (2 × A_r(H)) + (1 × A_r(O)) M_r(H_2O) = (2 × 1.0) + (1 × 16.0) M_r(H_2O) = 2.0 + 16.0 M_r(H_2O) = 18.0 The relative molecular mass of water is 18.0. 2) For Carbon Dioxide (CO_2): Step 1: Identify the atoms and their quantities. The molecule CO_2 contains 1 carbon atom and 2 oxygen atoms. Step 2: List the relative atomic masses. A_r(C) = 12.0 A_r(O) = 16.0 Step 3: Calculate the relative molecular mass. M_r(CO_2) = (1 × A_r(C)) + (2 × A_r(O)) M_r(CO_2) = (1 × 12.0) + (2 × 16.0) M_r(CO_2) = 12.0 + 32.0 M_r(CO_2) = 44.0 The relative molecular mass of carbon dioxide is 44.0. 3) For Methane (CH_4): Step 1: Identify the atoms and their quantities. The molecule CH_4 contains 1 carbon atom and 4 hydrogen atoms. Step 2: List the relative atomic masses. A_r(C) = 12.0 A_r(H) = 1.0 Step 3: Calculate the relative molecular mass. M_r(CH_4) = (1 × A_r(C)) + (4 × A_r(H)) M_r(CH_4) = (1 × 12.0) + (4 × 1.0) M_r(CH_4) = 12.0 + 4.0 M_r(CH_4) = 16.0 The relative molecular mass of methane is 16.0. That's 2 down. 3 left today — send the next one.