17.17 燃烧热
章节大纲
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What is gasohol?
::什么是气相醇?In efforts to reduce consumption from oil, ethanol is often added to regular gasoline. It has a high octane rating and burns more slowly than regular gas. This “gasohol” is widely used in many countries. It produces somewhat lower carbon monoxide and carbon dioxide emissions, but does increase air pollution from other materials.
::在减少石油消耗方面,乙醇往往被添加到常规汽油中,其辛烷含量高,燃烧速度比正常气体慢。 这种“加索醇”在许多国家被广泛使用。 它产生一氧化碳和二氧化碳排放量略低,但确实增加了其他材料的空气污染。Molar Heat of Combustion
::燃烧摩拉热热热Many are combustion reactions. It is often important to know the energy produced in such a reaction so we can determine which fuel might be the most efficient for a given purpose. The molar heat of combustion (ΔH c °) is the released when one mole of a substance is completely burned.
::许多是燃烧反应。 了解这种反应产生的能量往往很重要,这样我们才能确定哪些燃料对特定目的最有效。 燃烧的摩尔热(-Hc°)是当一种物质的一个摩尔完全燃烧时释放出来的。Typical combustion reactions involve the reaction of a carbon-containing material with oxygen to form carbon dioxide and water as products. If methanol is burned in air, we have:
::典型的燃烧反应涉及含碳的含氧材料的反应,以形成二氧化碳和水作为产品。
::CH3OH+O2CO2+2H2OH2OHc890千焦/摩尔In this case, one mole of oxygen reacts with one mole of methanol to form one mole of carbon dioxide and two moles of water.
::在这种情况下,一种氧的摩尔与一种甲醇的摩尔发生反应,形成一种二氧化碳的摩尔和两种水的摩尔。It should be noted that inorganic substances can also undergo a form of :
::应当指出,无机物质也可以有某种形式的:
::2兆克+O2+%2兆克OIn this case there is no water and no carbon dioxide formed. These reactions are generally not what we would be talking about when we discuss combustion reactions.
::在这种情况下,没有水,也没有形成二氧化碳。 这些反应通常不是我们在讨论燃烧反应时要谈论的。Sample Problem: Calculation of Heat of Combustion
::抽样问题:计算燃烧热量Heats of combustion are usually determined by burning a known amount of the material in a bomb calorimeter with an excess of oxygen. By measuring the temperature change, the heat of combustion can be determined.
::燃烧热通常通过用超氧量的炸弹卡路里计燃烧已知数量的材料来确定,通过测量温度变化,可以确定燃烧热。A 1.55 gram sample of ethanol is burned and produced a temperature increase of 55°C in 200 grams of water. Calculate the molar heat of combustion.
::乙醇的1.55克样本被焚烧,200克水的温度上升55°C,计算燃烧的摩尔热。Step 1: List the known quantities and plan the problem.
::第1步:列出已知数量并规划问题。Known
::已知已知-
mass of ethanol = 1.55 grams
::乙醇质量=1.55克 -
of ethanol = 46.1 g/mol
::乙醇=46.1克/摩尔 -
mass of water = 200 grams
::水质量=200克 -
::水:4.18 J/gC -
temperature increase = 55°C
::温度上升=55°C
Unknown
::未知-
ΔH
c
°
of ethanol
::乙醇浓度
Step 2: Solve .
::步骤2:解决。amount of ethanol used:
::1.55 g46.1 g/mol=0.0336 摩尔energy generated:
::产生能量: 4.184 J/gCx200 gx55C=46024 J=46.024 kJmolar heat of combustion:
::摩尔燃烧热: 46.024 kJ0.0336 摩尔= 1369 kJ/摩尔Step 3: Think about your result.
::步骤3:想想你的结果。The burning of ethanol produces a significant amount of heat.
::乙醇燃烧产生大量热量。Summary
::摘要-
The molar heat of combustion is defined.
::燃烧的摩尔热是有定义的。 -
Calculations using the molar heat of combustion are described.
::说明使用燃烧的摩尔热的计算方法。
Review
::回顾-
Write the reaction for the combustion of ethanol in oxygen?
::写下乙醇在氧气中燃烧的反应? -
What would be the limiting reactant in the reaction?
::反应中的限制反应者是什么? -
If you made an error in weighing the ethanol and added less than you planned on, would the heat of combustion result be higher or lower?
::如果你在乙醇重量方面犯了一个错误, 加的比计划少, 燃烧的热会更高还是更低?
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mass of ethanol = 1.55 grams