化学反应

AP 化学 · 第 4 主题

训练

讲义词汇表

4.1

化学反应导论

大纲

Learning Objective

Essential Knowledge

4.1.A
Identify evidence of chemical and physical changes in matter.

4.1.A.1 A physical change occurs when a substance undergoes a change in properties but not a change in composition. Changes in the phase of a substance (solid, liquid, gas) or formation/separation of mixtures of substances are common physical changes.
4.1.A.2 A chemical change occurs when substances are transformed into new substances, typically with different compositions. Production of heat or light, formation of a gas, formation of a precipitate, and/or color change provide possible evidence that a chemical change has occurred.

来源:美国大学理事会 AP 课程与考试说明

一个化学反应(chemical reaction)把原子重新排列成新物质。一个已经发生的迹象:一个颜色变化、一个气体或沉淀(precipitate)形成,或一个温度变化。原子守恒,所以一个方程必须配平(balanced)——两侧每个元素的数目相同。

词汇表训练

英文	中文	拼音
chemical reaction	化学反应	huà xué fǎn yìng
precipitate	沉淀	chén diàn

练习卷

4.2

净离子方程式

大纲

Learning Objective

Essential Knowledge

4.2.A
Represent changes in matter with a balanced chemical or net ionic equation:
i. For physical changes.
ii. For given information about the identity of the reactants and/or product.
iii. For ions in a given chemical reaction.

4.2.A.1 All physical and chemical processes can be represented symbolically by balanced equations.
4.2.A.2 Chemical equations represent chemical changes. These changes are the result of a rearrangement of atoms into new combinations; thus, any representation of a chemical change must contain equal numbers of atoms of every element before and after the change occurred. Equations thus demonstrate that mass and charge are conserved in chemical reactions.
4.2.A.3 Balanced molecular, complete ionic, and net ionic equations are differing symbolic forms used to represent a chemical reaction. The form used to represent the reaction depends on the context in which it is to be used.

来源:美国大学理事会 AP 课程与考试说明

对于在水里的反应,离子化合物分裂成离子。一个净离子方程式(net ionic equation)只显示实际变化的物种,略去在两侧不变出现的旁观离子(spectator ions)。它捕捉真正的化学(例如 $\text{Ag}^+ + \text{Cl}^- \rightarrow \text{AgCl}(s)$)。

混合两个溶液能形成一个不溶的沉淀

词汇表训练

英文	中文	拼音
net ionic equation	净离子方程式	jìng lí zi fāng chéng shì
spectator ions	旁观离子	páng guān lí zi

练习卷

4.3

反应的表示方法

大纲

Learning Objective	Essential Knowledge
4.3.A Represent a given chemical reaction or physical process with a consistent particulate model.	4.3.A.1 Balanced chemical equations in their various forms can be translated into symbolic particulate representations.

来源:美国大学理事会 AP 课程与考试说明

同一个反应能被显示为一个符号方程、一幅微粒图(原子和分子),和一个宏观观察(你看到的)。在这些层次之间移动——把方程连接到粒子连接到烧杯——是一项核心技能。

一个配平的方程两侧每个原子的数目相同

练习卷

4.4

物理变化与化学变化

大纲

Learning Objective

Essential Knowledge

4.4.A
Explain the relationship between macroscopic characteristics and bond interactions for:
i. Chemical processes.
ii. Physical processes.

4.4.A.1 Processes that involve the breaking and/or formation of chemical bonds are typically classified as chemical processes. Processes that involve only changes in intermolecular interactions, such as phase changes, are typically classified as physical processes.
4.4.A.2 Sometimes physical processes involve the breaking of chemical bonds. For example, plausible arguments could be made for the dissolution of a salt in water, as either a physical or chemical process, involves breaking of ionic bonds, and the formation of ion-dipole interactions between ions and solvent.

来源:美国大学理事会 AP 课程与考试说明

一个物理变化(physical change)改变形式但不改变身份(熔化、溶解);一个化学变化(chemical change)通过破坏和形成键制造新物质。溶解盐是物理的;盐不变并可回收。

词汇表训练

英文	中文	拼音
physical change	物理变化	wù lǐ biàn huà
chemical change	化学变化	huà xué biàn huà

练习卷

4.5

化学计量

大纲

Learning Objective

Essential Knowledge

4.5.A
Explain changes in the amounts of reactants and products based on the balanced reaction equation for a chemical process.

4.5.A.1 Because atoms must be conserved during a chemical process, it is possible to calculate product amounts by using known reactant amounts, or to calculate reactant amounts given known product amounts.
4.5.A.2 Coefficients of balanced chemical equations contain information regarding the proportionality of the amounts of substances involved in the reaction. These values can be used in chemical calculations involving the mole concept.
4.5.A.3 Stoichiometric calculations can be combined with the ideal gas law and calculations involving molarity to quantitatively study gases and solutions.

来源:美国大学理事会 AP 课程与考试说明

化学计量(stoichiometry)用配平方程的摩尔比来关联反应物和产物的量。路径总是克 → 摩尔 → (摩尔比) → 摩尔 → 克。限量反应物(limiting reactant)首先耗尽并设定最大产物(理论产量(theoretical yield));百分产率(percent yield)把实际与理论比较。

限量反应物首先耗尽并决定形成多少产物

Worked example. 当 $4.0\ \text{g}$ 的氢在过量氧里燃烧时形成多少水?$2\text{H}_2+\text{O}_2\rightarrow2\text{H}_2\text{O}$。转换成摩尔、跨过摩尔比(这里 $2:2=1:1$)、转换回:

$$n(\text{H}_2)=\frac{4.0}{2.0}=2.0\ \text{mol}\;\Rightarrow\;n(\text{H}_2\text{O})=2.0\ \text{mol}\;\Rightarrow\;m=2.0\times18=36\ \text{g}.$$

Worked example (limiting reactant). $10.0\ \text{g}$ 的 N$_2$ 与 $5.0\ \text{g}$ 的 H$_2$ 反应($\text{N}_2+3\text{H}_2\rightarrow2\text{NH}_3$)。哪个耗尽?摩尔:$n(\text{N}_2)=10.0/28=0.36$,$n(\text{H}_2)=5.0/2=2.5$。反应每 N$_2$ 需要 $3$ H$_2$;你有 $2.5/0.36=7.0$,远多于 $3$,所以 N$_2$ 是限量的。它制造 $2\times0.36=0.72\ \text{mol}$ 的氨,有氢剩余。

探索

Scale reactants and products by the mole ratio

A balanced equation fixes the mole ratio between species. Product amount is proportional to the limiting reactant, scaled by that ratio.

词汇表训练

英文	中文	拼音
Stoichiometry	化学计量	huà xué jì liàng
limiting reactant	限量反应物	xiàn liàng fǎn yìng wù
theoretical yield	理论产量	lǐ lùn chǎn liàng

练习卷

4.6

滴定导论

大纲

Learning Objective

Essential Knowledge

4.6.A
Identify the equivalence point in a titration based on the amounts of the titrant and analyte, assuming the titration reaction goes to completion.

4.6.A.1 Titrations may be used to determine the amount of an analyte in solution. The titrant has a known concentration of a species that reacts specifically and quantitatively with the analyte. The equivalence point of the titration occurs when the analyte is totally consumed by the reacting species in the titrant. The equivalence point is often indicated by a change in a property (such as color) that occurs when the equivalence point is reached. This observable event is called the endpoint of the titration.

来源:美国大学理事会 AP 课程与考试说明

酸碱滴定曲线

一个滴定(titration)通过把一个未知浓度与一个已知浓度的溶液反应直到它们达到等当点(equivalence point)(化学计量相等)来求它。从已知的体积和浓度,用摩尔比来求未知的。一个指示剂(indicator)或一条 pH 曲线发出终点信号。

滴定装置:一个滴定管把一个已知溶液送入一个锥形瓶

Worked example. $25.0\ \text{mL}$ 的盐酸被 $30.0\ \text{mL}$ 的 $0.100\ \text{M}$ NaOH 恰好中和。求酸的浓度。反应是 $1:1$,所以摩尔匹配:

$$n(\text{NaOH})=0.0300\times0.100=3.00\times10^{-3}\ \text{mol}=n(\text{HCl}),\qquad [\text{HCl}]=\frac{3.00\times10^{-3}}{0.0250}=0.120\ \text{M}.$$

A titration setup: reacting volumes from a burette find the concentration of an unknown solution

探索

Titrate an acid and find the equivalence point

Adding base to acid raises the pH slowly, then sharply at the equivalence point where moles of acid and base are equal. The steep jump locates that volume.

词汇表训练

英文	中文	拼音
titration	滴定	dī dìng
equivalence point	等当点	děng dāng diǎn

练习卷

4.7

化学反应的类型

大纲

Learning Objective

Essential Knowledge

4.7.A
Identify a reaction as acid-base, oxidation-reduction, or precipitation.

4.7.A.1 Acid-base reactions involve transfer of one or more protons ($\text{H}^+$ ions) between chemical species.
4.7.A.2 Oxidation-reduction (redox) reactions involve transfer of one or more electrons between chemical species, as indicated by changes in oxidation numbers of the involved species. Combustion is an important subclass of oxidation-reduction reactions, in which a species reacts with oxygen gas. In the case of hydrocarbons, carbon dioxide and water are products of complete combustion.
4.7.A.3 In a redox reaction, electrons are transferred from the species that is oxidized to the species that is reduced.
- Exclusion statement: The meaning of the terms "reducing agent" and "oxidizing agent" will not be assessed on the AP Exam.
4.7.A.4 Oxidation numbers may be assigned to each of the atoms in the reactants and products; this is often an effective way to identify the oxidized and reduced species in a redox reaction.
4.7.A.5 Precipitation reactions frequently involve mixing ions in aqueous solution to produce an insoluble or sparingly soluble ionic compound. All sodium, potassium, ammonium, and nitrate salts are soluble in water.
- Exclusion statement: Rote memorization of "solubility rules" other than those implied in 4.7.A.5 will not be assessed on the AP Exam.

来源:美国大学理事会 AP 课程与考试说明

常见的模式包括化合(synthesis)(结合)、分解(decomposition)(拆开)、燃烧(combustion)(与氧,释放能量)、沉淀(precipitation)(形成一个不溶的固体)、酸-碱(acid–base)(质子转移),和氧化还原(redox)(电子转移)。辨认类型帮助预测产物。

词汇表训练

英文	中文	拼音
acid	酸	suān
base	碱	jiǎn
redox	氧化还原	yǎng huà huán yuán

练习卷

4.8

酸碱反应导论

大纲

Learning Objective

Essential Knowledge

4.8.A
Identify species as Brønsted-Lowry acids, bases, and/or conjugate acid-base pairs, based on proton-transfer involving those species.

4.8.A.1 By definition, a Brønsted-Lowry acid is a proton donor and a Brønsted-Lowry base is a proton acceptor.
4.8.A.2 Only in aqueous solutions, water plays an important role in many acid-base reactions, as its molecular structure allows it to accept protons from and donate protons to dissolved species.
4.8.A.3 When an acid or base ionizes in water, the conjugate acid-base pairs can be identified and their relative strengths compared.
- Exclusion statement: Lewis acid-base concepts will not be assessed on the AP Exam. The emphasis in AP Chemistry is on reactions in aqueous solution.

来源:美国大学理事会 AP 课程与考试说明

一个酸(acid)给出一个质子($\text{H}^+$);一个碱(base)接受一个(布朗斯特-劳里)。它们反应形成水和一个盐:$\text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O}$。强酸和强碱完全解离;弱的只部分。

布朗斯特-劳里:一个酸把一个质子给一个碱,形成两个共轭对

探索

Move along the pH scale

pH measures how acidic or basic a solution is. Each step of 1 pH is a tenfold change in hydrogen-ion concentration; 7 is neutral, below is acidic, above is basic.

练习卷

4.9

氧化还原反应

大纲

Learning Objective	Essential Knowledge
4.9.A Represent a balanced redox reaction equation using half-reactions.	4.9.A.1 Balanced chemical equations for redox reactions can be constructed from half-reactions.

来源:美国大学理事会 AP 课程与考试说明

在一个氧化还原(redox)反应里,电子在物种之间转移。氧化(oxidation)是电子的失去(氧化数上升);还原(reduction)是获得(氧化数下降)。用氧化数(oxidation numbers)追踪变化,并记住每个氧化与一个还原配对——失去的电子等于获得的电子。

氧化还原是电子转移:还原剂被氧化、氧化剂被还原

Worked example. 求高锰酸盐 $\text{KMnO}_4$ 里锰的氧化数。钾是 $+1$ 而每个氧是 $-2$(四个,$-8$)。整个公式是中性的,所以 $(+1)+\text{Mn}+(-8)=0$,给出 $\text{Mn}=+7$ ——它的最大值,这就是为什么高锰酸盐是一个强的氧化剂(它只能获得电子)。

探索

Watch electrons transfer in a redox reaction

In a redox reaction one species is oxidised (loses electrons) and another is reduced (gains them). Follow the electrons move from the metal to the non-metal.

词汇表训练

英文	中文	拼音
Oxidation	氧化	yǎng huà
reduction	还原	huán yuán

练习卷

4.9

考试技巧

配平每个方程并以摩尔工作——转换克→摩尔、跨过摩尔比,然后转换回。
通过比较摩尔比找到限量反应物;它设定最大产物(理论产量)。
在氧化还原里,记住 OIL RIG:氧化是电子的失去(Oxidation Is Loss)、还原是获得(Reduction Is Gain);每个氧化与一个还原配对。
对于滴定用配平的比在等当点联系已知和未知。
一个净离子方程式只显示变化的物种;略去旁观离子。

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