📚 Complete and Incomplete Combustion | 完全燃烧与不完全燃烧
Combustion reactions power transport, heating and electricity generation, yet many AQA exam questions test the difference between complete and incomplete combustion. This article reviews definitions, equations, energy changes, oxidation states, practical tests and environmental consequences.
燃烧反应驱动交通、供暖和发电，但许多AQA考题会考察完全燃烧与不完全燃烧的区别。本文复习定义、方程式、能量变化、氧化数、实验检验和环境后果。
1. Defining Combustion | 燃烧的定义
Combustion is an exothermic redox reaction in which a fuel reacts rapidly with an oxidant, normally oxygen. For hydrocarbon fuels, carbon and hydrogen are oxidised while oxygen is reduced.
燃烧是一种放热的氧化还原反应，燃料与氧化剂（通常是氧气）快速反应。对于碳氢化合物燃料，碳和氢被氧化，氧被还原。
In AQA terminology, complete combustion occurs when there is a plentiful supply of oxygen, producing carbon dioxide and water only. Incomplete combustion occurs when oxygen is limited, leading to carbon monoxide, solid carbon or both.
在AQA术语中，完全燃烧发生在氧气充足时，只生成二氧化碳和水；不完全燃烧发生在氧气不足时，会生成一氧化碳、固体碳或两者兼有。
2. Complete Combustion of Alkanes | 烷烃的完全燃烧
The general equation for complete combustion of an alkane is:
烷烃完全燃烧的通式如下：
CₙH₂ₙ₊₂ + (3n+1)/2 O₂ → n CO₂ + (n+1) H₂O
For methane and propane, the balanced equations are:
以甲烷和丙烷为例，配平后的方程式为：
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)
Complete combustion releases the maximum chemical energy stored in the fuel because carbon is fully oxidised to carbon dioxide.
完全燃烧释放燃料中储存的最大化学能，因为碳被完全氧化为二氧化碳。
3. Incomplete Combustion of Alkanes | 烷烃的不完全燃烧
When the oxygen supply is restricted, carbon may be only partially oxidised. The most important incomplete combustion product is carbon monoxide, CO, but solid carbon particles, known as soot, can also form.
当氧气供应受限时，碳可能只被部分氧化。最重要的不完全燃烧产物是一氧化碳CO，但也会形成固体碳颗粒，即炭黑。
Two typical incomplete combustion equations for methane are:
甲烷不完全燃烧的两个典型方程式为：
2CH₄(g) + 3O₂(g) → 2CO(g) + 4H₂O(g)
CH₄(g) + O₂(g) → C(s) + 2H₂O(g)
In car engines, incomplete combustion produces CO, unburned hydrocarbons and soot, especially during cold starts or when the air-to-fuel ratio is too low.
在汽车发动机中，不完全燃烧会产生CO、未燃烧的碳氢化合物和炭黑，尤其是在冷启动或空燃比过低时。
4. Balanced Equations and Mole Ratios | 配平方程式与摩尔比
Balancing combustion equations requires careful accounting of oxygen. A simple method is to balance carbon first, then hydrogen, and finally oxygen.
配平燃烧方程式需要仔细计算氧原子数。一个简单的方法是先配平碳，再配平氢，最后配平氧。
O. This gives 13 oxygen atoms on the right, so 13/2 O₂ is needed, or multiply through by 2 to give:
以丁烷C₄H₁₀的完全燃烧为例，先写出C₄H₁₀ + O₂ → 4CO₂ + 5H₂O。右边共有13个氧原子，因此需要13/2个O₂，或者整体乘以2得到：
2C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(g)
Exam questions often ask for the volume of oxygen required to burn a given volume of a gaseous alkane. Use Avogadro's law: equal volumes of gases at the same temperature and pressure contain equal numbers of moles.
考题经常要求计算燃烧一定体积气态烷烃所需的氧气体积。使用阿伏伽德罗定律：同温同压下，相同体积的气体含有相同的物质的量。
5. Conditions Affecting Combustion Type | 影响燃烧类型的条件
The type of combustion depends mainly on the availability of oxygen, the air-to-fuel ratio, mixing and temperature. A plentiful oxygen supply favours complete combustion.
燃烧类型主要取决于氧气的供应量、空燃比、混合程度和温度。氧气充足有利于完全燃烧。
In a Bunsen burner, a fully open air hole allows enough oxygen for complete combustion, giving a blue flame with little light. A closed air hole restricts oxygen, causing incomplete combustion and a yellow, luminous, sooty flame.
在本生灯中，空气孔完全打开时氧气充足，发生完全燃烧，火焰呈蓝色且几乎不光亮；空气孔关闭时氧气受限，发生不完全燃烧，火焰呈黄色、明亮并产生炭黑。
In internal combustion engines, a fuel-rich mixture may produce more power but also more CO and soot emissions.
在内燃机中，富燃料混合气可能产生更多动力，但也会排放更多CO和炭黑。
6. Products and Their Identification | 产物及其检验
Carbon dioxide can be identified by bubbling the gas through limewater, which turns milky due to the formation of insoluble calcium carbonate.
二氧化碳可通过将气体通入石灰水来检验，石灰水因生成不溶性碳酸钙而变浑浊。
Water can be detected using anhydrous copper(II) sulfate, which changes from white to blue, or by observing condensation on a cold surface.
水可通过无水硫酸铜检验，颜色由白色变为蓝色，或通过观察冷表面上的冷凝现象来检测。
Carbon monoxide is much harder to identify directly in the school laboratory. Its presence is usually inferred from a yellow, sooty flame or from incomplete combustion conditions.
一氧化碳在学校实验室中很难直接检验。通常通过黄色、带炭黑的火焰或根据不完全燃烧条件来推断其存在。
7. Oxidation Numbers in Combustion | 燃烧中的氧化数
Oxidation numbers provide a useful way to show that combustion is a redox reaction. In methane, carbon has an oxidation number of -4; in carbon dioxide it is +4, and in carbon monoxide it is +2.
氧化数可以有效地说明燃烧是氧化还原反应。在甲烷中，碳的氧化数为-4；在二氧化碳中为+4，在一氧化碳中为+2。
Oxygen is reduced from 0 in O₂ to -2 in H₂O and CO₂. Carbon is oxidised from negative values in the fuel to positive values in the products.
氧从O₂中的0价被还原为H₂O和CO₂中的-2价。碳从燃料中的负价被氧化为产物中的正价。
In incomplete combustion, the smaller increase in carbon's oxidation number from -4 to +2 in CO shows that less oxidation has occurred.
在不完全燃烧中，碳的氧化数从-4仅增加到CO中的+2，表明氧化程度较低。
8. Energy Released: Enthalpy of Combustion | 释放的能量：燃烧焓
The standard enthalpy change of combustion, ΔcH°, is the enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions, with all reactants and products in their standard states.
标准燃烧焓变ΔcH°是指在标准条件下，1摩尔物质在氧气中完全燃烧时的焓变，所有反应物和产物均处于标准状态。
Combustion is always exothermic, so ΔcH° values are always negative. Complete combustion releases more energy per mole than incomplete combustion because carbon is fully oxidised.
燃烧总是放热的，因此ΔcH°值总是负值。完全燃烧每摩尔释放的能量比不完全燃烧多，因为碳被完全氧化。
ed is calculated using q = mcΔT, and the molar enthalpy change is found using ΔH = -q / n.
在简单的量热实验中，传递的能量用q = mcΔT计算，摩尔焓变用ΔH = -q / n求得。
9. Environmental and Health Impacts | 环境与健康影响
Carbon monoxide is highly toxic because it binds strongly to haemoglobin in red blood cells, forming carboxyhaemoglobin and reducing the blood's ability to carry oxygen.
一氧化碳具有剧毒，因为它与红细胞中的血红蛋白强结合，形成碳氧血红蛋白，降低血液输送氧气的能力。
Solid carbon particles, or soot, can worsen respiratory conditions such as asthma and contribute to blackening of buildings. Unburned hydrocarbons contribute to photochemical smog.
固体碳颗粒即炭黑会加重哮喘等呼吸系统疾病，并使建筑物变黑。未燃烧的碳氢化合物会促进光化学烟雾的形成。
Carbon dioxide from complete combustion is a major greenhouse gas, driving global warming and climate change.
完全燃烧产生的二氧化碳是一种主要的温室气体，导致全球变暖和气候变化。
10. Catalytic Converters and Complete Oxidation | 催化转化器与完全氧化
Catalytic converters in vehicle exhaust systems use platinum, palladium and rhodium catalysts to promote more complete oxidation of harmful gases.
汽车排气系统中的催化转化器使用铂、钯和铑催化剂，促进有害气体更完全的氧化。
Key reactions include the oxidation of carbon monoxide to carbon dioxide and the reduction of nitrogen monoxide to nitrogen:
关键反应包括一氧化碳氧化为二氧化碳，以及一氧化氮还原为氮气：
2CO(g) + O₂(g) → 2CO₂(g)
2NO(g) + 2CO(g) → N₂(g) + 2CO₂(g)
Unburned hydrocarbons such as CₓHᵧ are also oxidised to CO₂ and H₂O, helping to reduce emissions from incomplete combustion.
未燃烧的碳氢化合物如CₓHᵧ也会被氧化为CO₂和H₂O，有助于减少不完全燃烧产生的排放。
11. Practical Measurement of Combustion Products | 燃烧产物的实验测量
In the laboratory, a spirit burner can burn a liquid fuel under a copper calorimeter containing a known mass of water. The temperature rise allows the enthalpy change of combustion to be estimated.
在实验室中，可以用酒精灯在装有已知质量水的铜量热器下方燃烧液体燃料。通过测量温升可以估算燃烧焓变。
To collect and test combustion products, the gases from a burning candle or gas flame can be drawn through anhydrous copper sulfate and limewater in sequence.
为了收集并检验燃烧产物，可以将蜡烛或气体火焰产生的气体依次通过无水硫酸铜和石灰水。
Accurate enthalpy values require insulation, stirring, and corrections for heat loss to the surroundings, which are common sources of error in AQA required practicals.
准确的焓值需要隔热、搅拌以及对周围环境散热进行校正，这些是AQA必修实验中常见的误差来源。
12. Exam Tips for AQA | AQA考试提示
Learn the definition of standard enthalpy change of combustion word-for-word, and always quote 'oxygen under standard conditions' and 'one mole of substance'.
请逐字记住标准燃烧焓变的定义，并始终写出“标准条件下的氧气”和“1摩尔物质”。
When writing equations, balance carbon and hydrogen before oxygen. State symbols are often required, so include (g), (l) and (s) where appropriate.
书写方程式时，先配平碳和氢，再配平氧。通常需要写出状态符号，因此在适当位置标注(g)、(l)和(s)。
O formation and soot. In calculations, show all steps when using q = mcΔT and ΔH = -q / n.
在回答不完全燃烧时，明确联系氧气供应不足、CO的生成和炭黑。在计算题中，使用q = mcΔT和ΔH = -q / n时要展示所有步骤。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图