ac{24.0}{1000} = 3.6 \\times 10^{-4}\\text{ mol}$ A1","marks":1,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"direct_calculation","label":"Direct Calculation","steps":[{"type":"text","order":0,"title":"Identify the key values","content":"To calculate the amount of bromine ($\\text{Br}_2$) in moles, we need to identify two values from the question and previous experimental data:\n1. The concentration of the bromine solution: $0.015\\text{ mol dm}^{-3}$\n2. The volume of the target titre: $24.0\\text{ cm}^3$ (obtained from the titration results)","highlights":[{"text":"0.015 mol dm^{-3}","location":"specification"}]},{"type":"hyper_latex","block":{"nodes":[{"latex":"$$\\text{Volume in dm}^3 = \\frac{\\htmlData{anchor=vol-cm}{\\color{@sky}{24.0}} \\text{ cm}^3}{\\htmlData{anchor=conversion}{\\color{@amber}{1000}}}$"},{"latex":"$$\\text{Volume} = \\htmlData{anchor=vol-dm}{\\color{@purple}{0.0240}} \\text{ dm}^3$"}],"highlights":[{"color":"sky","style":"text-color","anchor":"vol-cm"},{"color":"amber","style":"text-color","anchor":"conversion"},{"color":"purple","style":"text-color","anchor":"vol-dm"}],"connections":[{"to":"vol-dm","from":"vol-cm","color":"sky","label":"divided by 1000","style":"solid"}]},"order":1,"title":"Convert volume units","description":"Concentration is given in $\\text{mol dm}^{-3}$, so we must convert the titre volume from $\\text{cm}^3$ to $\\text{dm}^3$ by dividing by $1000$."},{"type":"text","order":2,"title":"Calculate the moles","content":"Now, apply the direct formula to calculate the number of moles ($n$):\n\n$$\\text{Moles } (n) = \\text{Concentration } (c) \\times \\text{Volume in dm}^3 (V)$$\n\n$$\\text{Moles of } \\text{Br}_2 = 0.015\\text{ mol dm}^{-3} \\times 0.0240\\text{ dm}^3 = 3.6 \\times 10^{-4}\\text{ mol}$$\n\nThis simple, direct calculation gives us the final amount of bromine in the target titre, earning the 1 mark available.","calculator":[{"gdc":{"expression":"0.015 * 0.0240","instructions":"Type: 0.015 * 0.0240"},"ti84":{"expression":"0.015 * (24.0 / 1000)","instructions":"Enter: 0.015 * (24.0 / 1000)"},"desmos":{"expression":"0.015 * (24.0 / 1000)","instructions":"Type the multiplication directly to see the scientific notation result."},"description":"Calculate the product of concentration and converted volume."}]}]}],"generatedAt":"2026-06-11T09:49:48.145Z","modelVersion":"gemini-3.5-flash","explanationVersion":"v2"},"options":[]},{"id":"6052198f-68af-4a4d-92b4-86cd6576ab86","label":"2","content":"Calculate a suitable mass of the cosmetic wax to transfer to the volumetric flask using your answer to Part 1 and the chemical structure of $\\text{Y}$. Assume that the wax contains $75.0\\%$ of $\\text{Y}$ by mass. (If you were unable to calculate the amount of bromine in the target titre, you should assume it is $3.0 \\times 10^{-4}\\text{ mol}$. This is **not** the correct amount.)","markscheme":"- Deduces that the reacting ratio of $\\text{Y} : \\text{Br}_2$ is $1:3$ (as $\\text{Y}$ contains 3 double bonds) and calculates moles of $\\text{Y}$ in the $20.0\\text{ cm}^3$ sample: $\\frac{3.6 \\times 10^{-4}}{3} = 1.2 \\times 10^{-4}\\text{ mol}$ M1\n- Calculates moles of $\\text{Y}$ in the $100\\text{ cm}^3$ volumetric flask: $1.2 \\times 10^{-4} \\times \\frac{100.0}{20.0} = 6.0 \\times 10^{-4}\\text{ mol}$ (or $5.0 \\times 10^{-4}\\text{ mol}$ from the alternative value) M1\n- Calculates mass of $\\text{Y}$ in the flask: $6.0 \\times 10^{-4} \\times 616 = 0.3696\\text{ g}$ (or $5.0 \\times 10^{-4} \\times 616 = 0.308\\text{ g}$ from the alternative value) M1\n- Calculates the total required mass of wax accounting for $75.0\\%$ purity: $\\frac{0.3696}{0.750} \\approx 0.493\\text{ g}$ (or $\\frac{0.308}{0.750} \\approx 0.411\\text{ g}$ from the alternative value) A1","marks":4,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"analyte_scaling","label":"Stepwise Scaling of Analyte","steps":[{"type":"text","order":0,"title":"Analyze the reaction ratio","content":"To determine th

Amount of substance

Question 50

Amount of substance Questions

Amount of substance

Question 50

Amount of substance Questions