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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Question One Table 1: Mass of solid A (Na₂S₂O₃) The data for the mass of solid A is not provided in Table 1. Therefore, the initial concentration of solution A cannot be calculated. Table 2: Temperature change during reaction of A with water The provided temperature data is: Time/min: 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 Temp/°C: 25, 25, 25, 25, 25, 25, 25, XXX, 25, 25, 25, 25, 25, 25, 25 The temperature at 3.5 minutes is marked "XXX", which is when solid A was added. All subsequent temperatures remain at 25 °C. Step 1: Calculate T. Since the temperature remains constant at 25 \,^C after the addition of solid A, the change in temperature is: T = T_final - T_initial = 25 \,^C - 25 \,^C = 0 \,^ Table 3: Titration data The data for the burette readings and titre is not provided in Table 3. Therefore, the mean titre cannot be calculated. Calculations 1. Calculate the molarity of solution A and solution B. The question asks to determine the concentration of solution B using solution A, and then asks to calculate the molarity of solution A using the titre. This implies a standardisation of solution B using solution A, where solution A's concentration is either known or determined first. Given the procedure, solution A (Na₂S₂O₃) is prepared from a weighed mass, so its concentration can be calculated. Then, solution B (K₂Cr₂O₇) is titrated with solution A. Step 1: Calculate the molarity of solution A (Na₂S₂O₃). This requires the mass of solid A from Table 1. Molar mass of Na₂S₂O₃ = (2 × 22.99) + (2 × 32.07) + (3 × 16.00) = 158.11 \, g/mol. If the mass of solid A (Na₂S₂O₃) was m grams, and it was dissolved in 250 \, cm^3 (0.250 \, dm^3) of water: Moles of Na_2S_2O_3 = Mass of Na_2S_2O_3Molar mass of Na_2S_2O_3 = (m)/(158.11) \, mol Molarity of solution A = Moles of Na_2S_2O_3Volume of solution (in dm^3) = \