📚 AS AQA Chemistry Unit 2 Question Paper Insert (Jan 20) | AQA AS 化学第二单元试题插页（2020年1月）
The insert for an AQA AS Chemistry Unit 2 paper is not just a set of tables – it is a toolkit. In the January 2020 series, the insert provided key thermodynamic values, spectral data and reaction sequences that candidates needed to interpret in order to answer the questions. This article unpacks the most common concepts tested alongside such inserts, with paired English and Chinese explanations.
AQA AS 化学第二单元试卷的插页不仅仅是一组表格——它是答题的工具包。在2020年1月的考试系列中，插页提供了关键的热力学数值、光谱数据和反应序列，考生需要解读这些信息才能回答问题。本文将结合中英文配对讲解，解析这类插页中最常考查的核心概念。
1. Enthalpy Changes and Hess’s Law | 焓变与赫斯定律
Enthalpy change (ΔH) is the heat energy change at constant pressure. The insert often gives mean bond enthalpies or standard enthalpies of formation and combustion. You may be asked to calculate the enthalpy change of a reaction using a Hess cycle.
焓变（ΔH）是在恒压条件下的热能变化。插页通常会给出平均键焓或标准生成焓与燃烧焓。你可能会被要求使用赫斯循环计算反应的焓变。
For example, with bond enthalpies: ΔH = Σ(bonds broken) – Σ(bonds formed). Remember to account for all bonds in both reactants and products.
例如，使用键焓：ΔH = Σ(断裂键) – Σ(形成键)。注意要计算反应物和产物中的所有化学键。
ΔH = Σ E(reactant bonds) − Σ E(product bonds)
In the January insert, you might have found a table of mean bond enthalpies, allowing you to estimate ΔH for combustion or substitution reactions. Always check whether the question asks for a diagram of the Hess cycle or just the numerical value.
在一月的插页中，你可能会看到平均键焓表，用以估算燃烧或取代反应的ΔH。注意题目要求画出赫斯循环图还是仅计算数值。
2. Rates of Reaction and the Boltzmann Distribution | 反应速率与玻尔兹曼分布
Rates are affected by concentration, pressure, temperature, surface area and catalysts. The insert may show a Boltzmann distribution curve to illustrate the effect of temperature or a catalyst on the number of particles with energy exceeding the activation energy.
反应速率受浓度、压强、温度、表面积和催化剂的影响。插页可能显示玻尔兹曼分布曲线，用于说明温度或催化剂对超过活化能的粒子数目的影响。
Key points: for a catalyst, the curve is unchanged but the activation energy (Eₐ) is lowered, so the shaded area under the curve beyond Eₐ increases. For a temperature rise, the whole curve shifts to the right and flattens, and the most probable energy increases.
要点：对于催化剂，曲线形状不变但活化能（Eₐ）降低，因此曲线下超过Eₐ的阴影面积增大。对于温度升高，整条曲线右移并变得平坦，最概然能量增大。
When using the insert, look for labels showing Eₐ and the mean energy. You must be able to draw the new curve on the same axes for a higher temperature or catalyst.
使用插页时，注意寻找标有Eₐ和平均能量的位置。你需要能够在同一坐标轴上画出温度升高或加入催化剂后的新曲线。
3. Dynamic Equilibria and Le Chatelier’s Principle | 动态平衡与勒夏特列原理
A dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction in a closed system. The insert might include a concentration–time or rate–time graph showing when equilibrium is reached.
动态平衡是在封闭系统中正逆反应速率相等时达到的状态。插页可能包含浓度-时间或速率-时间图，显示何时达到平衡。
Le Chatelier’s principle states that if a system at equilibrium is subjected to a change, the position of equilibrium moves to counteract that change. This explains the effects of changing temperature, pressure or concentration.
勒夏特列原理指出，如果处于平衡的系统受到改变，平衡位置会向抵消该改变的方向移动。这解释了温度、压强或浓度变化的影响。
For example, in the Haber process N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = –92 kJ mol⁻¹, increasing pressure shifts the equilibrium to the right (fewer moles of gas), while increasing temperature shifts it to the left (endothermic reverse).
例如，在哈伯法中 N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = –92 kJ mol⁻¹，增大压强使平衡右移（气体摩尔数减少），升高温度则使平衡左移（逆向吸热）。
4. Equilibrium Constants: Kc and Kp | 平衡常数：Kc 与 Kp
The insert may provide equilibrium concentrations or partial pressures for a reaction. You would then calculate Kc = [products] / [reactants] with each term raised to the power of its stoichiometric coefficient.
插页可能提供反应的平衡浓度或分压。你将计算 Kc = [生成物] / [反应物]，各项的幂指数为其化学计量系数。
Kc = [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ
For gaseous reactions, Kp is expressed in terms of partial pressures. Units of Kc or Kp depend on the total change in moles of gas; you must derive them from the balanced equation. The insert often gives initial amounts and equilibrium moles, so practice constructing an ICE (Initial-Change-Equilibrium) table.
对于气相反应，Kp 用分压表示。Kc 或 Kp 的单位取决于气体总摩尔数的变化；你必须根据配平方程式推导。插页常给出初始量和平衡摩尔数，因此要练习构建 ICE（初始-变化-平衡）表。
Remember: pure solids and liquids are omitted from K expressions. Also, temperature changes alter K, while changes in pressure or concentration do not.
记住：纯固体和纯液体不出现在K表达式中。此外，温度改变会改变K，而压强或浓度变化不会。
5. Oxidation, Reduction and Redox Equations | 氧化、还原与氧化还原方程式
Oxidation is loss of electrons, reduction is gain of electrons. The insert might contain standard electrode potentials or an electrochemical series to help you predict spontaneity.
氧化是失去电子，还原是得到电子。插页可能包含标准电极电势或电化学序，帮助预测反应自发性。
You may need to combine half-equations to produce a full redox equation. Make sure electrons cancel and the number of atoms and charges balance.
你可能需要组合半方程式得到完整氧化还原方程式。确保电子抵消，且原子数和电荷数平衡。
For example, acidified dichromate(VI) oxidises ethanol to ethanal: Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O, combined with the oxidation of ethanol.
例如，酸化的重铬酸根氧化乙醇成乙醛：Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O，再与乙醇的氧化半反应结合。
In the January 2020 insert, you might have seen redox titrations or oxidation state changes. Practise assigning oxidation numbers to every element in a formula.
在2020年1月的插页中，你可能会看到氧化还原滴定或氧化态变化。练习给每个元素指定氧化数。
6. Organic Chemistry: Alkanes and Alkenes | 有机化学：烷烃与烯烃
Alkanes are saturated hydrocarbons, undergoing free-radical substitution with halogens in UV light. The reaction mechanism involves initiation, propagation and termination steps, which are often tested using the insert to suggest products.
烷烃是饱和烃，在紫外光下与卤素发生自由基取代。反应机理包括引发、增长和终止步骤，插页可能提示产物。
Alkenes are unsaturated and undergo electrophilic addition reactions, e.g. with bromine water, hydrogen halides or steam. Markovnikov’s rule may be tested for asymmetric alkenes.
烯烃是不饱和烃，发生亲电加成反应，例如与溴水、卤化氢或水蒸气反应。不对称烯烃可能考查马氏规则。
The insert might contain a reaction scheme showing the synthesis of an alcohol from an alkene, or the polymerisation of an alkene. Identify functional groups and count carbons carefully.
插页可能包含由烯烃合成醇的反应路线，或烯烃的聚合。仔细识别官能团并数清碳原子。
7. Organic Reactions: Halogenoalkanes and Alcohols | 有机反应：卤代烷与醇
Halogenoalkanes undergo nucleophilic substitution with aqueous hydroxide, or elimination with alcoholic hydroxide. The insert may give data about the rate of hydrolysis of different halogenoalkanes, linking to bond enthalpy.
卤代烷与氢氧化物水溶液发生亲核取代，或与醇性氢氧化物发生消除。插页可能给出不同卤代烷水解速率的数据，与键焓相关联。
Alcohols can be oxidised to aldehydes, ketones or carboxylic acids. Primary alcohols oxidise to aldehydes then carboxylic acids; secondary alcohols oxidise to ketones; tertiary alcohols do not oxidise.
醇可被氧化成醛、酮或羧酸。伯醇先氧化成醛再氧化成羧酸；仲醇氧化成酮；叔醇不被氧化。
Using the insert, you might be asked to distinguish between a primary and tertiary alcohol by referencing a colour change of acidified dichromate from orange to green, or by IR spectra of the product.
利用插页，你可能会被要求通过酸化的重铬酸盐从橙色变为绿色来区分伯醇和叔醇，或通过产物的红外光谱。
8. Spectroscopic Techniques: IR and Mass Spectrometry | 光谱技术：红外与质谱
Infrared (IR) spectroscopy is used to identify functional groups by characteristic absorptions. The insert may include an IR table with wavenumbers for O–H, C=O, C–O, etc.
红外光谱用于通过特征吸收峰鉴定官能团。插页可能包含红外表，列出O–H、C=O、C–O等的波数。
Mass spectrometry gives the relative molecular mass from the molecular ion peak and structural information from fragmentation patterns. The insert may show a mass spectrum with labelled peaks, which you must assign to fragment ions.
质谱通过分子离子峰给出相对分子质量，通过碎片模式给出结构信息。插页可能显示标有峰值的质谱图，你需要将碎片峰归属。
For example, a peak at m/z 29 often corresponds to C₂H₅⁺ or CHO⁺, while m/z 43 corresponds to C₃H₇⁺ or CH₃CO⁺. Always account for isotopes and charges.
例如，m/z 29 的峰通常对应 C₂H₅⁺ 或 CHO⁺，而 m/z 43 对应 C₃H₇⁺ 或 CH₃CO⁺。始终考虑同位素和电荷。
When answering questions on the January 2020 insert, look at the wavenumber ranges given in the table—do not memorise exact values, but interpret them correctly. For IR, mention the specific bond and vibration.
回答2020年1月插页的问题时，查看表格给出的波数范围——不要死记硬背具体数值，而要正确解读。对于红外，要指出具体的键和振动类型。
9. Using the Insert: Data Analysis and Calculations | 利用插页：数据分析与计算
The insert is designed to save you from memorising data, but you must know how to apply it. Common tasks include reading a titration curve, determining the endpoint, or calculating an average titre.
插页的设计是为了避免你记忆数据，但你必须知道如何应用。常见任务包括读取滴定曲线、确定终点或计算平均滴定体积。
You may also be asked to use the insert to find a bond enthalpy, an enthalpy of formation, or an activation energy from an Arrhenius plot. In every case, show your working and include units.
你可能需要插页寻找键焓、生成焓，或从阿伦尼乌斯图中读取活化能。无论如何，都要写出计算过程并带上单位。
For calculations involving the ideal gas equation pV = nRT, the insert may give the value of R. Use the correct units (usually J K⁻¹ mol⁻¹) and convert pressure to Pa, volume to m³.
对于使用理想气体方程 pV = nRT 的计算，插页可能给出 R 的值。使用正确的单位（通常为 J K⁻¹ mol⁻¹），并将压强转换为 Pa，体积转换为 m³。
Always check whether the question gives the data in kJ or J; a common error is failing to convert between them.
始终检查题目给出的数据单位是 kJ 还是 J；一个常见错误是忘记换算。
10. Exam Tips: Common Pitfalls | 考试技巧：常见误区
Read the insert before the question: it gives you a hint about the topic. For example, a table of infrared absorptions suggests an organic question with functional group identification.
先阅读插页再做题目：它会提示你主题。例如，红外吸收表暗示涉及官能团鉴定的有机题。
Be precise with terminology: ‘breaking bonds’ is endothermic, ‘forming bonds’ is exothermic. In equilibrium questions, say ‘position of equilibrium’ not ‘equilibrium constant’ unless asked.
术语要精确：“断裂键”是吸热，“形成键”是放热。在平衡问题中，除非题目要求，否则说“平衡位置”而不是“平衡常数”。
For organic mechanisms, draw curly arrows exactly and show dipole bonds. For redox, balance charges with electrons. For data interpretation, quote numbers from the insert with units.
对于有机机理，准确画出弯箭头并显示极性键。对于氧化还原，用电子平衡电荷。对于数据解读，引用插页中的数值并带单位。
Finally, use the insert as a safety net. If you cannot remember whether an alcohol is primary or secondary, check the IR table for the C–O stretch position or the mass spectrum for fragment masses.
最后，把插页当作安全网。如果你记不住醇是伯醇还是仲醇，查看红外表中 C–O 伸缩位置或质谱中的碎片质量。
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