反应热热

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How are diamonds made?
::钻石是如何制造的?

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Natural diamonds are mined from sites around the world. However, the price of natural diamonds is carefully controlled, so other sources for diamonds are being explored. Several different methods for producing synthetic diamonds are available, usually involving treating carbon at very high temperatures and pressures. The diamonds produced are now of high quality, but are primarily used in industrial applications. Diamonds are one of the hardest materials available and are widely used for cutting and grinding tools.
::天然钻石是从世界各地开采的,但天然钻石的价格受到谨慎控制,因此正在探讨其他钻石来源,有几种生产合成钻石的不同方法,通常涉及在极高的温度和压力下处理碳,生产的钻石现在质量很高,但主要用于工业用途,钻石是最难获得的材料之一,广泛用于切割和研磨工具。

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Calculating Heat of Reaction from Heat of Formation
::调制热反应反应的计算热热量

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An application of Hess’s law allows us to use standard heats of formation to indirectly calculate the heat of reaction for any reaction that occurs at standard conditions. An change that occurs specifically under standard conditions is called the standard enthalpy (or heat) of reaction and is given the symbol $\begin{array}{r}\mathrm{\Delta }{H}^{\circ }\end{array}$ . The standard heat of reaction can be calculated by using the following equation.
::赫斯法的运用允许我们使用标准电热来间接计算在标准条件下发生的任何反应的反应热。 在标准条件下具体发生的变化被称为标准(或热 ) , 并给它一个符号。 标准电热反应可以通过以下方程式来计算。

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::HnHf(产品) nHff(反应剂)

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The symbol Σ is the Greek letter sigma and means “the sum of”. The standard heat of reaction is equal to the sum of all the standard heats of formation of the products minus the sum of all the standard heats of formation of the reactants . The symbol “ $\begin{array}{r}n\end{array}$ ” signifies that each of formation must first be multiplied by its coefficient in the balanced equation .
::标准反应热等于产品形成的所有标准热量总和减去反应器形成的所有标准热量总和。 “n”符号表示每个形成系数必须首先乘以平衡方程中的系数。

Standard Heats of Formation of Selected Substances

Substance	$\begin{array}{r}\mathrm{\Delta }{H}_f^{\circ }\end{array}$   (kJ/mol)	Substance	$\begin{array}{r}\mathrm{\Delta }{H}_f^{\circ }\end{array}$   (kJ/mol)
Al 2 O 3 (s)	-1669.8	H 2 O 2 (l)	-187.6
BaCl 2 (s)	-860.1	KCl(s)	-435.87
Br 2 (g)	30.91	NH 3 (g)	-46.3
C (s, graphite)	0	NO(g)	90.4
C (s, diamond)	1.90	NO 2 (g)	33.85
CH 4 (g)	-74.85	NaCl	-411.0
C 2 H 5 OH(l)	-276.98	O 3 (g)	142.2
CO(g)	-110.5	P(s, white)	0
CO 2 (g)	-393.5	P(s, red)	-18.4
CaO(s)	-635.6	PbO(s)	-217.86
CaCO 3 (s)	-1206.9	S(rhombic)	0
HCl(g)	-92.3	S(monoclinic)	0.30
CuO(s)	-155.2	SO 2 (g)	-296.1
CuSO 4 (s)	-769.86	SO 3 (g)	-395.2
Fe 2 O 3 (s)	-822.2	H 2 S(g)	-20.15
H 2 O(g)	-241.8	SiO 2	-859.3
H 2 O(l)	-285.8	ZnCl 2	-415.89

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Sample Problem: Calculating Standard Heat of Reaction
::抽样问题:计算反应标准热量

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Calculate the standard heat of reaction  $\begin{array}{r}(\mathrm{\Delta }{H}^{\circ })\end{array}$ for the reaction of nitrogen monoxide with oxygen to form nitrogen dioxide gas.
::计算一氧化氮与氧反应形成二氧化氮气体的标准反应热(H) 。

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Step 1: List the known quantities and plan the problem .
::第1步:列出已知数量并规划问题。

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Known
::已知已知

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• $\begin{array}{r}\mathrm{\Delta }H{{}_f}^{\circ }\text{for NO}(\text{g})=90.4\text{ kJ/mol}\end{array}$
  ::NO(g)=90.4 kJ/mol
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• $\begin{array}{r}\mathrm{\Delta }H{{}_f}^{\circ }{\text{for O}}_2(\text{g})=0(\text{element})\end{array}$
  ::O2(g)=0 (元素)
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• $\begin{array}{r}\mathrm{\Delta }H{{}_f}^{\circ }{\text{for NO}}_2(\text{g})=33.85\text{ kJ/mol}\end{array}$
  ::NO2(g)=33.85 kJ/mol

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Unknown
::未知

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• $\begin{array}{r}\mathrm{\Delta }{H}^{\circ }=?\text{ kJ}\end{array}$
  ::哈?

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First write the balanced equation for the reaction. Then apply the equation to calculate the standard heat of reaction for the standard heats of formation.
::首先写入反应的平衡方程式。 然后应用方程式来计算标准形成热的标准反应热。

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Step 2: Solve .
::步骤2:解决。

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The balanced equation is: $\begin{array}{r}2\text{NO(g)}+{\text{O}}_2(\text{g})\to 2{\text{NO}}_2(\text{g})\end{array}$
::平衡方程是: 2NO(g)+O2(g)+2NO2(g)+2NO2(g)

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Applying the equation form the text:
::应用方程式的文本 :

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::*H[2 mol NO2(33.85 kJ/mol)] -[2 mol NO(90.4 kJ/mol)+1 mol O2(0 kJ/mol)]113 kJ

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The standard heat of reaction is -113 kJ.
::标准反应热为-113 kJ。

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Step 3: Think about your result .
::步骤3:想想你的结果。

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The reaction is exothermic , which makes sense because it is a and combustion reactions always release heat.
::反应是过热的,这是有道理的,因为它是一种燃烧反应, 燃烧反应总是释放热量。

 

 

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Summary
::摘要

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• Standard heats of reaction can be calculated from standard heats of formation.
  ::标准反应热可以从标准形成热中计算出来。

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Review
::回顾

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1. Is a Hess’s Law calculation a direct determination of a standard heat of reaction?
   ::a 赫斯定律计算是否直接确定标准反应热?
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2. What is the purpose of the  $\begin{array}{r}n\end{array}$ in the equation?
   ::等式中n的目的是什么?
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3. What does  $\begin{array}{r}\sum \end{array}$ stand for?
   ::这代表什么?