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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Q11. An 8.4g sample of hydrogen (H, containing carbon and hydrogen atoms only) contains 7.2g of carbon (C). (Relative atomic mass of hydrogen (H) = 1 and carbon (C) = 12) a. What is the empirical formula of this compound? Step 1: Calculate the mass of hydrogen (H). The total mass of the compound is 8.4 g, and the mass of carbon is 7.2 g. Mass of H = Total mass of compound - Mass of C \\ Mass of H = 8.4 g - 7.2 g \\ Mass of H = 1.2 g Step 2: Convert the mass of each element to moles. Moles of C = Mass of CRelative atomic mass of C = 7.2 g12 g/mol = 0.6 mol \\ Moles of H = Mass of HRelative atomic mass of H = 1.2 g1 g/mol = 1.2 mol Step 3: Find the simplest whole number ratio of moles. Divide the number of moles of each element by the smallest number of moles (which is 0.6 mol). Ratio of C = 0.6 mol0.6 mol = 1 \\ Ratio of H = 1.2 mol0.6 mol = 2 The simplest whole number ratio of C:H is 1:2. Step 4: Write the empirical formula. The empirical formula is CH_2. b. If this compound has a molar mass of 84, what is its molecular formula? Step 1: Calculate the empirical formula mass. Empirical formula = CH_2 Empirical formula mass = (1 × Relative atomic mass of C) + (2 × Relative atomic mass of H) \\ Empirical formula mass = (1 × 12) + (2 × 1) \\ Empirical formula mass = 12 + 2 = 14 g/mol Step 2: Determine the ratio (n) between the molar mass and the empirical formula mass. Given molar mass = 84 g/mol. n = Molar massEmpirical formula mass \\ n = 84 g/mol14 g/mol \\ n = 6 Step 3: Multiply the subscripts in the empirical formula by n to get the molecular formula. Molecular formula = (Empirical formula)_n = (CH_2)_6 Molecular formula = C_6H_12