IB Chemistry HL — Reactivity 1: What Drives Chemical Reactions?

IB-Style Practice Questions — Reactivity 1.1–1.4IB 风格练习题 —— 覆盖 Reactivity 1.1–1.4

Multiple Choice选择题

Each item carries 1 mark. No calculator, no data booklet. Items tagged HL test content beyond the standard-level syllabus (entropy, Gibbs energy, Born–Haber cycles).每题 1 分。不可使用计算器与数据手册（data booklet）。标记 HL 的题目考查超出标准级别（SL）大纲的内容：熵（entropy）、吉布斯自由能（Gibbs energy）、玻恩-哈伯循环（Born–Haber cycle）。

Q1EASY Paper 1 1.1 Exo/Endo Signs [1]

Which combination of observations correctly describes an exothermic reaction?下列哪一组描述正确对应一个放热反应？

(A) Temperature of surroundings decreases; $\Delta H$ negative; products more stable than reactants.环境温度降低；$\Delta H$ 为负；产物比反应物更稳定。
(B) Temperature of surroundings increases; $\Delta H$ negative; products more stable than reactants.环境温度升高；$\Delta H$ 为负；产物比反应物更稳定。
(C) Temperature of surroundings increases; $\Delta H$ positive; products less stable than reactants.环境温度升高；$\Delta H$ 为正；产物比反应物更不稳定。
(D) Temperature of surroundings decreases; $\Delta H$ positive; products less stable than reactants.环境温度降低；$\Delta H$ 为正；产物比反应物更不稳定。

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Q2MEDIUM Paper 1 1.1 Calorimetry Sign [1]

In a calorimetry experiment, the temperature of the water surrounding a reaction vessel increases. Which statement correctly gives the sign of $\Delta H$ for the reaction, with the correct reason?在一次量热实验中，反应容器周围的水温升高。下列哪一项正确给出了反应 $\Delta H$ 的符号及其理由？

(A) $\Delta H$ positive, because the reaction absorbed heat from the water.$\Delta H$ 为正，因为反应从水中吸收了热量。
(B) $\Delta H$ negative, because the reaction released heat to the water.$\Delta H$ 为负，因为反应向水释放了热量。
(C) $\Delta H$ positive, simply because the water's temperature increased.$\Delta H$ 为正，仅仅因为水的温度升高了。
(D) $\Delta H$ negative, because the water's temperature decreased.$\Delta H$ 为负，因为水的温度降低了。

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Q3MEDIUM Paper 1 1.2 Bond Enthalpy Direction [1]

Using average bond enthalpies, the enthalpy change of a reaction is calculated as用平均键能计算反应焓变时，正确的表达式是

(A) $\sum(\text{bonds formed}) - \sum(\text{bonds broken})$$\sum(\text{成键}) - \sum(\text{断键})$
(B) $\sum(\text{bonds broken}) - \sum(\text{bonds formed})$$\sum(\text{断键}) - \sum(\text{成键})$
(C) $\sum(\text{bonds broken}) + \sum(\text{bonds formed})$$\sum(\text{断键}) + \sum(\text{成键})$
(D) $-[\sum(\text{bonds broken}) + \sum(\text{bonds formed})]$$-[\sum(\text{断键}) + \sum(\text{成键})]$

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Q4MEDIUM Paper 1 1.2 Hess's Law: Combustion Data [1]

Using standard enthalpies of combustion, $\Delta H^\ominus$ for a reaction is correctly calculated as用标准燃烧焓计算反应的 $\Delta H^\ominus$ 时，正确的表达式是

(A) $\Delta H^\ominus = \sum \Delta H_f^\ominus(\text{products}) - \sum \Delta H_f^\ominus(\text{reactants})$
(B) $\Delta H^\ominus = \sum \Delta H_c^\ominus(\text{products}) - \sum \Delta H_c^\ominus(\text{reactants})$
(C) $\Delta H^\ominus = \sum \Delta H_c^\ominus(\text{reactants}) - \sum \Delta H_c^\ominus(\text{products})$
(D) $\Delta H^\ominus = \sum \Delta H_c^\ominus(\text{reactants}) + \sum \Delta H_c^\ominus(\text{products})$

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Q5MEDIUM Paper 1 1.3 Incomplete Combustion [1]

Which statement best explains why larger hydrocarbon molecules are more prone to incomplete combustion than smaller ones, under the same oxygen supply?在相同供氧条件下，为何较大的烃分子比较小的烃分子更容易发生不完全燃烧？下列哪一项解释最合理？

(A) Larger molecules have weaker C–H bonds, which break more easily.较大分子的 C–H 键更弱，更容易断裂。
(B) Larger molecules require more $\mathrm{O_2}$ per mole burned, so a fixed oxygen supply is depleted (locally) before combustion completes.较大分子每摩尔燃烧所需 $\mathrm{O_2}$ 更多，因此固定的供氧量（局部）在燃烧完成前就被耗尽。
(C) Larger molecules have lower boiling points, so they vaporize before reacting.较大分子沸点更低，会在反应前先汽化。
(D) Larger molecules always undergo complete combustion to only $\mathrm{CO_2}$.较大分子总是完全燃烧只生成 $\mathrm{CO_2}$。

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Q6MEDIUM Paper 1 1.3 Fuel Cells [1]

Which statement about hydrogen fuel cells is correct?关于氢燃料电池，下列哪一项陈述是正确的？

(A) Hydrogen is reduced at the anode.氢气在阳极被还原。
(B) The only product of the overall cell reaction is water.整个电池反应唯一的产物是水。
(C) Fuel cells release $\mathrm{CO_2}$ as a byproduct, like combustion.燃料电池像燃烧一样会释放 $\mathrm{CO_2}$ 副产物。
(D) Fuel cells store chemical energy without ever converting it to electrical energy.燃料电池只储存化学能，从不将其转化为电能。

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Q7HARD Paper 1 HL 1.4 Entropy Prediction [1]

For which of the following reactions would $\Delta S^\ominus$ be expected to be most positive?下列哪个反应的 $\Delta S^\ominus$ 预期最正（增大最多）？

(A) $2\mathrm{SO_2(g)} + \mathrm{O_2(g)} \rightarrow 2\mathrm{SO_3(g)}$
(B) $\mathrm{CaCO_3(s)} \rightarrow \mathrm{CaO(s)} + \mathrm{CO_2(g)}$
(C) $\mathrm{N_2(g)} + 3\mathrm{H_2(g)} \rightarrow 2\mathrm{NH_3(g)}$
(D) $\mathrm{H_2O(g)} \rightarrow \mathrm{H_2O(l)}$

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Structured Response结构化解答题

Show all working in the space provided. Marks for correct method are awarded even if the final numerical answer is wrong. State units and significant figures appropriately.在指定区域写出全部解题过程。即便最终数值错误，方法正确仍可得分。注意单位与有效数字（significant figures）。

SR 1MEDIUM Paper 2 1.1 Calorimetry + Hess's Law [14]

A student determines the enthalpy of combustion of ethanol using a spirit burner to heat water in a calorimeter. A mass of $200.0~\mathrm{g}$ of water is heated from $21.0~\mathrm{°C}$ to $47.5~\mathrm{°C}$. The spirit burner (with ethanol) has mass $87.42~\mathrm{g}$ before burning and $86.57~\mathrm{g}$ after burning.某学生用酒精灯燃烧乙醇加热量热计中的水，以测定乙醇的燃烧焓。$200.0~\mathrm{g}$ 水从 $21.0~\mathrm{°C}$ 升温至 $47.5~\mathrm{°C}$。酒精灯（含乙醇）燃烧前质量为 $87.42~\mathrm{g}$，燃烧后为 $86.57~\mathrm{g}$。

(a) Calculate the heat absorbed by the water, the amount (in mol) of ethanol burned, and hence the experimental enthalpy of combustion of ethanol, $\Delta H_c^\ominus(\mathrm{exp})$, in $\mathrm{kJ\,mol^{-1}}$. ($c(\mathrm{H_2O}) = 4.18~\mathrm{J\,g^{-1}\,K^{-1}}$; molar mass of $\mathrm{C_2H_5OH} = 46.08~\mathrm{g\,mol^{-1}}$)计算水吸收的热量、燃烧的乙醇的量（单位 mol），并求出乙醇的实验燃烧焓 $\Delta H_c^\ominus(\mathrm{exp})$（单位 $\mathrm{kJ\,mol^{-1}}$）。（$c(\mathrm{H_2O}) = 4.18~\mathrm{J\,g^{-1}\,K^{-1}}$；$\mathrm{C_2H_5OH}$ 摩尔质量 $= 46.08~\mathrm{g\,mol^{-1}}$） [4]

(b) The data-booklet (theoretical) magnitude of $\Delta H_c^\ominus$ for ethanol is considerably larger than the experimental value from part (a). Suggest three distinct reasons for this discrepancy.数据手册（理论值）给出的乙醇 $\Delta H_c^\ominus$ 大小远大于 (a) 中的实验值。请提出三个不同的原因来解释这一差异。 [3]

(c) Given $\Delta H_f^\ominus(\mathrm{C_2H_5OH,\,l}) = -278~\mathrm{kJ\,mol^{-1}}$, $\Delta H_f^\ominus(\mathrm{CO_2,\,g}) = -394~\mathrm{kJ\,mol^{-1}}$, and $\Delta H_f^\ominus(\mathrm{H_2O,\,l}) = -286~\mathrm{kJ\,mol^{-1}}$, use Hess's law to calculate the theoretical $\Delta H_c^\ominus$ of ethanol for $\mathrm{C_2H_5OH(l)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{CO_2(g)} + 3\mathrm{H_2O(l)}$, and compare it (as a percentage difference) with your answer to (a).已知 $\Delta H_f^\ominus(\mathrm{C_2H_5OH,\,l}) = -278~\mathrm{kJ\,mol^{-1}}$，$\Delta H_f^\ominus(\mathrm{CO_2,\,g}) = -394~\mathrm{kJ\,mol^{-1}}$，$\Delta H_f^\ominus(\mathrm{H_2O,\,l}) = -286~\mathrm{kJ\,mol^{-1}}$，用盖斯定律计算反应 $\mathrm{C_2H_5OH(l)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{CO_2(g)} + 3\mathrm{H_2O(l)}$ 的理论 $\Delta H_c^\ominus$，并与 (a) 的结果比较（给出百分比差异）。 [4]

(d) Suggest one modification to the apparatus that would reduce heat loss to the surroundings, and briefly explain why it works.建议一项能减少向环境散热的装置改进，并简要说明其原理。 [3]

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SR 2HARD Paper 2 HL 1.4 Entropy + Gibbs Energy + Equilibrium [14]

Dinitrogen tetroxide dissociates according to: $\mathrm{N_2O_4(g)} \rightleftharpoons 2\mathrm{NO_2(g)}$, $\Delta H^\ominus = +57.2~\mathrm{kJ\,mol^{-1}}$. Standard entropy values: $S^\ominus(\mathrm{N_2O_4,\,g}) = 304~\mathrm{J\,K^{-1}\,mol^{-1}}$, $S^\ominus(\mathrm{NO_2,\,g}) = 240~\mathrm{J\,K^{-1}\,mol^{-1}}$.四氧化二氮按下式解离：$\mathrm{N_2O_4(g)} \rightleftharpoons 2\mathrm{NO_2(g)}$，$\Delta H^\ominus = +57.2~\mathrm{kJ\,mol^{-1}}$。标准熵值：$S^\ominus(\mathrm{N_2O_4,\,g}) = 304~\mathrm{J\,K^{-1}\,mol^{-1}}$，$S^\ominus(\mathrm{NO_2,\,g}) = 240~\mathrm{J\,K^{-1}\,mol^{-1}}$。

(a) Calculate $\Delta S^\ominus$ for the reaction as written.计算上述反应的 $\Delta S^\ominus$。 [3]

(b) Calculate $\Delta G^\ominus$ at 298 K. Comment on whether the forward reaction is spontaneous at this temperature.计算 298 K 时的 $\Delta G^\ominus$，并说明正反应在此温度下是否自发。 [3]

(d) Using $\Delta G^\ominus = -RT\ln K$ and $R = 8.314~\mathrm{J\,K^{-1}\,mol^{-1}}$, calculate the equilibrium constant $K$ at 298 K. State whether reactants or products are favored at 298 K, and explain how your value of $K$ is consistent with your answer to (b).用 $\Delta G^\ominus = -RT\ln K$（$R = 8.314~\mathrm{J\,K^{-1}\,mol^{-1}}$）计算 298 K 时的平衡常数 $K$。说明 298 K 时是反应物还是产物占优，并解释你所得的 $K$ 值如何与 (b) 的结论一致。 [3]

(e) State one reason, in terms of particles and disorder, why $\Delta S^\ominus$ for this reaction is positive.从粒子数与混乱度的角度，说明该反应 $\Delta S^\ominus$ 为正的一个原因。 [2]

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SR 3HARD Paper 2 1.2 Bond Enthalpies vs Formation Data [15]

Consider the complete combustion of propane in the gas phase: $\mathrm{C_3H_8(g)} + 5\mathrm{O_2(g)} \rightarrow 3\mathrm{CO_2(g)} + 4\mathrm{H_2O(g)}$.考虑丙烷在气相中的完全燃烧：$\mathrm{C_3H_8(g)} + 5\mathrm{O_2(g)} \rightarrow 3\mathrm{CO_2(g)} + 4\mathrm{H_2O(g)}$。

Bond键	C–C	C–H	O=O	C=O	O–H
Bond enthalpy (kJ mol⁻¹)键能（kJ mol⁻¹）	346	414	498	804	463

(a) Using the average bond enthalpies given, calculate $\Delta H$ for this reaction. Show clearly the bonds broken and the bonds formed.用给定的平均键能计算该反应的 $\Delta H$。清楚列出断裂的键与形成的键。 [5]

(b) Given $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g}) = -104~\mathrm{kJ\,mol^{-1}}$, $\Delta H_f^\ominus(\mathrm{CO_2,\,g}) = -394~\mathrm{kJ\,mol^{-1}}$, and $\Delta H_f^\ominus(\mathrm{H_2O,\,g}) = -242~\mathrm{kJ\,mol^{-1}}$, calculate $\Delta H$ for the same reaction using standard enthalpies of formation.已知 $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g}) = -104~\mathrm{kJ\,mol^{-1}}$，$\Delta H_f^\ominus(\mathrm{CO_2,\,g}) = -394~\mathrm{kJ\,mol^{-1}}$，$\Delta H_f^\ominus(\mathrm{H_2O,\,g}) = -242~\mathrm{kJ\,mol^{-1}}$，用标准生成焓计算同一反应的 $\Delta H$。 [4]

(c) Compare the two values obtained in (a) and (b). Explain briefly why they are not identical, referencing the nature of "average" bond enthalpies.比较 (a) 与 (b) 所得的两个值。结合"平均"键能的本质，简要解释二者为何不完全相同。 [3]

(d) $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g})$ cannot be measured directly, since carbon and hydrogen do not react cleanly to form propane. Using Hess's law, suggest how $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g})$ could instead be determined indirectly from combustion data. Give the general expression in terms of enthalpies of combustion.碳与氢气不能干净地直接反应生成丙烷，因此 $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g})$ 无法直接测量。利用盖斯定律，说明如何用燃烧焓数据间接求出 $\Delta H_f^\ominus(\mathrm{C_3H_8,\,g})$。写出以燃烧焓表示的一般表达式。 [3]

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Data-Based Questions (HL)数据题（HL）

These questions test the experimental skills and data analysis associated with Reactivity 1. Higher-level students should attempt all parts.本部分考查与 Reactivity 1 相关的实验技能与数据分析能力。HL 学生应作答全部小题。

P3-1HARD Paper 3 HL 1.3 Fuels, Energy Density & Emissions [15]

A team compares two liquid fuels, methanol and octane, as candidates for a small generator.某研究小组为一台小型发电机比较两种液体燃料：甲醇与辛烷。

Fuel燃料	Formula分子式	Molar mass (g mol⁻¹)摩尔质量（g mol⁻¹）	$\Delta H_c^\ominus$ (kJ mol⁻¹)
Methanol甲醇	$\mathrm{CH_3OH(l)}$	$32.05$	$-726$
Octane辛烷	$\mathrm{C_8H_{18}(l)}$	$114.26$	$-5470$

(a) Calculate the energy released per gram (in $\mathrm{kJ\,g^{-1}}$) for each fuel. State which fuel has the higher energy density by mass.计算每种燃料每克释放的能量（单位 $\mathrm{kJ\,g^{-1}}$），并指出哪种燃料的单位质量能量密度更高。 [4]

(b) The complete combustion of octane is: $\mathrm{C_8H_{18}(l)} + \tfrac{25}{2}\mathrm{O_2(g)} \rightarrow 8\mathrm{CO_2(g)} + 9\mathrm{H_2O(l)}$. Calculate the mass of $\mathrm{CO_2}$ (in g) produced per MJ of energy released from burning octane. (Molar mass $\mathrm{CO_2} = 44.01~\mathrm{g\,mol^{-1}}$)辛烷完全燃烧：$\mathrm{C_8H_{18}(l)} + \tfrac{25}{2}\mathrm{O_2(g)} \rightarrow 8\mathrm{CO_2(g)} + 9\mathrm{H_2O(l)}$。计算辛烷燃烧每释放 1 MJ 能量所产生 $\mathrm{CO_2}$ 的质量（单位 g）。（$\mathrm{CO_2}$ 摩尔质量 $= 44.01~\mathrm{g\,mol^{-1}}$） [4]

(c) A supplier markets a bioethanol blend as "carbon neutral." Discuss, with reference to production energy inputs, whether this label is fully justified.某供应商将其生物乙醇混合燃料宣传为"碳中和"。结合生产过程的能量投入，讨论这一说法是否完全站得住脚。 [3]

(d) Evaluate hydrogen fuel cells as an alternative to hydrocarbon combustion for powering the generator. Refer to both an advantage and a limitation.评价氢燃料电池作为该发电机烃类燃烧替代方案的可行性。须同时提及一项优点与一项局限。 [4]

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P3-2HARD Paper 3 HL HL 1.2 Born–Haber Cycle [15]

A Born–Haber cycle is constructed for magnesium oxide, $\mathrm{MgO(s)}$. The lattice enthalpy $\Delta H_{\text{latt}}^\ominus$ is defined for $\mathrm{Mg^{2+}(g)} + \mathrm{O^{2-}(g)} \rightarrow \mathrm{MgO(s)}$. The following data are given.为氧化镁 $\mathrm{MgO(s)}$ 构建玻恩-哈伯循环。晶格焓 $\Delta H_{\text{latt}}^\ominus$ 定义为 $\mathrm{Mg^{2+}(g)} + \mathrm{O^{2-}(g)} \rightarrow \mathrm{MgO(s)}$ 对应的焓变。给出以下数据。

Step步骤	Atomization of MgMg 原子化	$IE_1(\mathrm{Mg})$	$IE_2(\mathrm{Mg})$	Atomization of OO 原子化	$EA_1(\mathrm{O})$	$EA_2(\mathrm{O})$	$\Delta H_f^\ominus(\mathrm{MgO})$
kJ mol⁻¹	$+148$	$+738$	$+1451$	$+249$	$-141$	$+798$	$-602$

(a) State the meaning of "electron affinity," and explain why the second electron affinity of oxygen, $EA_2(\mathrm{O})$ (i.e. $\mathrm{O^-(g)} + e^- \rightarrow \mathrm{O^{2-}(g)}$), is endothermic even though electron affinities are usually exothermic.说明"电子亲和能"的含义，并解释为何氧的第二电子亲和能 $EA_2(\mathrm{O})$（即 $\mathrm{O^-(g)} + e^- \rightarrow \mathrm{O^{2-}(g)}$）是吸热的，尽管电子亲和能通常是放热的。 [2]

(b) Using the Born–Haber cycle and the data given, calculate the lattice enthalpy $\Delta H_{\text{latt}}^\ominus(\mathrm{MgO})$.利用玻恩-哈伯循环及所给数据，计算晶格焓 $\Delta H_{\text{latt}}^\ominus(\mathrm{MgO})$。 [6]

(c) The lattice enthalpy of $\mathrm{CaO}$ is considerably less exothermic than that of $\mathrm{MgO}$, even though both compounds have $2+$ and $2-$ ions. Using the factors that determine lattice enthalpy magnitude, explain this trend.尽管 $\mathrm{CaO}$ 与 $\mathrm{MgO}$ 都由 $2+$、$2-$ 离子组成，$\mathrm{CaO}$ 的晶格焓放热程度却明显小于 $\mathrm{MgO}$。请用决定晶格焓大小的因素解释这一趋势。 [4]

(d) For a compound such as $\mathrm{AgCl}$, the Born–Haber (experimental) lattice enthalpy differs significantly from the value predicted by a purely ionic (theoretical) model, whereas for $\mathrm{MgO}$ the two agree much more closely. Explain this difference in terms of ionic polarization.对于 $\mathrm{AgCl}$ 这类化合物，玻恩-哈伯循环得到的（实验）晶格焓与纯离子模型（理论）预测值差异显著，而 $\mathrm{MgO}$ 的两者则吻合得多。请用离子极化的概念解释这一差异。 [3]

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Thermochemistry & Spontaneity热化学与自发性

Multiple Choice选择题

Structured Response结构化解答题

Data-Based Questions (HL)数据题（HL）