e into two identical halves, meaning any carbon atom on the left side of the line has an identical environment to its counterpart on the right side."},{"type":"hyper_latex","block":{"nodes":[{"latex":"$$\\text{Environment 1 (} C_1 \\text{): } \\htmlData{anchor=env1}{\\text{C-OH}}$"},{"latex":"$$\\text{Environment 2 (} C_4 \\text{): } \\htmlData{anchor=env2}{\\text{C-Cl}}$"},{"latex":"$$\\text{Environment 3 (} C_2, C_6 \\text{): } \\htmlData{anchor=env3}{\\text{C-H (adjacent to C-OH)}}$"},{"latex":"$$\\text{Environment 4 (} C_3, C_5 \\text{): } \\htmlData{anchor=env4}{\\text{C-CH}_3 \\text{ (ring carbon)}}$"},{"latex":"$$\\text{Environment 5 (} C_{\\text{methyl-3}}, C_{\\text{methyl-5}} \\text{): } \\htmlData{anchor=env5}{\\text{-CH}_3 \\text{ (methyl carbon)}}$"}],"highlights":[{"color":"sky","style":"text-color","anchor":"env1"},{"color":"sky","style":"text-color","anchor":"env2"},{"color":"amber","style":"text-color","anchor":"env3"},{"color":"purple","style":"text-color","anchor":"env4"},{"color":"green","style":"text-color","anchor":"env5"}],"connections":[{"to":"env2","from":"env1","color":"sky","label":"Axis of symmetry","style":"dashed"}]},"order":3,"title":"Map and Group Environments","description":"Now, we group the labeled carbons based on whether they share identical chemical environments due to this symmetry:"},{"type":"text","order":4,"title":"Determine the Peak Count","content":"Each unique carbon environment produces exactly one peak in a $^{13}\\text{C}$ NMR spectrum.\n\nSince we have mapped the 8 carbon atoms into **5 unique environments**, there will be:\n\n$$\\text{Number of peaks} = 5$$"}]}],"generatedAt":"2026-06-11T08:39:11.776Z","modelVersion":"gemini-3.5-flash","explanationVersion":"v2"},"options":[]},{"id":"f018e540-d11c-41d2-89ee-ff0a4841ebde","label":"c","content":"A student measures the pH of an antiseptic solution containing chloroxylenol to be 5.22.\n\nThe label on the bottle shows the percentage of chloroxylenol in the solution as 3.13% (weight/volume), meaning \$100\\text{ cm}^3\$ of the solution contains \$3.13\\text{ g}\$ of chloroxylenol.\n\nAssume the following:\n* Chloroxylenol is the only acidic component in the solution.\n* Chloroxylenol is a weak monobasic acid.\n* The density of the solution is \$1.00\\text{ g cm}^{-3}\$.\n\nWrite the equation, using molecular formulae, for the acid dissociation of chloroxylenol, and calculate the acid dissociation constant, \$K_{\\text{a}}\$, for chloroxylenol.","markscheme":"- Writes the correct dissociation equation: $\\text{C}_8\\text{H}_9\\text{ClO} \\rightleftharpoons \\text{H}^+ + \\text{C}_8\\text{H}_8\\text{ClO}^-$ (or with $\\text{H}_2\\text{O}$ / single arrow) M1\n- Calculates the molar mass of chloroxylenol ($M_{\\text{r}} = 156.5$) M1\n- Calculates the concentration of chloroxylenol in the antiseptic solution: $[\\text{HA}] = \\frac{31.3\\text{ g dm}^{-3}}{156.5\\text{ g mol}^{-1}} = 0.200\\text{ mol dm}^{-3}$ M1\n- Calculates $[\\text{H}^+] = 10^{-5.22} = 6.03 \\times 10^{-6}\\text{ mol dm}^{-3}$ M1\n- Calculates the acid dissociation constant: $K_{\\text{a}} = \\frac{[\\text{H}^+]^2}{[\\text{HA}]} = \\frac{(6.026 \\times 10^{-6})^2}{0.200} = 1.82 \\times 10^{-10}\\text{ mol dm}^{-3}$ (accept $1.81 \\times 10^{-10}$ to $1.82 \\times 10^{-10}$) A1","marks":5,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"standard_analytical","label":"Standard Analytical Approach","steps":[{"type":"text","order":0,"title":"Determine the molecular formula","content":"To write the dissociation equation, we first need to find the molecular formula of chloroxylenol from its chemical structure:\n* It has a benzene ring containing $6$ carbon atoms.\n* There are two methyl ($-\\text{CH}_3$) groups, adding $2$ more carbon atoms. Total carbon atoms = $8$ ($\\text{C}_8$).\n* For the hydrogen atoms, we have: $3$ from each of the two methyl groups ($6$), $2$ on the unsubstituted positions of the benzene ring ($2$), and $1$ in the phenol group ($-\\text{OH}$). Total

Acids, bases and buffers

Question 15

Acids, bases and buffers Questions

Acids, bases and buffers

Question 15

Acids, bases and buffers Questions