Comparisons of reaction heat and related calculation rules
1. **反应热大小比较规则** - **根据物质状态判断**：当物质由固态变为液态再变为气态时，这个过程需要吸收热量。所以在比较反应热大小时，如果反应产物状态不同，气态产物对应的反应通常比液态产物对应的反应吸收更多热量（反应热数值更大且为正值），液态产物对应的反应比固态产物对应的反应吸收更多热量（反应热数值更大且为正值）;反之，在放热反应中，气态反应物变为液态或固态反应物时，反应放出的热量更多（反应热数值更大且为负值）。 - **根据反应类型判断**：不同类型的反应热效应不同。例如，燃烧反应通常是放热反应，反应热为负值;而分解反应有些是吸热反应，反应热为正值。一般来说，放热反应的反应热（\(\Delta H\)）数值小于0，放热越多，\(\Delta H\)数值越小;吸热反应的反应热（\(\Delta H\)）数值大于0，吸热越多，\(\Delta H\)数值越大。 - **根据化学计量数判断**：在热化学方程式中，反应热数值与各物质的化学计量数成正比。例如，对于反应\(aA + bB=cC + dD\)，如果化学计量数变为\(2aA + 2bB = 2cC+2dD\)，则反应热\(\Delta H\)也变为原来的2倍。在比较反应热大小时，如果两个反应相似，化学计量数大的反应，其反应热数值也会按比例增大（吸热反应增大正值，放热反应增大负值）。 2. **反应热计算规则** - **根据盖斯定律计算** - 首先要明确所求反应的始态和终态、各物质的化学计量数及反应的吸、放热情况。不同途径对应的最终结果应一样。 - 当热化学方程式乘以或除以某一个数时，\(\Delta H\)也应乘以或除以同一个数;方程式进行加减运算时，\(\Delta H\)也同样要进行加减运算，注意各步反应\(\Delta H\)的正负。 - 将一个热化学方程式逆向书写时，\(\Delta H\)的符号也随之改变，但绝对值不变。 - **根据标准摩尔生成焓计算（定温定压过程）**：反应的标准摩尔焓变等于产物的标准摩尔生成焓之和减去反应物的标准摩尔生成焓之和，即\(\Delta_{r}H_{m}=\sum\Delta_{f}H_{m}\)（总生成物）\(-\sum\Delta_{f}H_{m}\)（总反应物）（如果有参考状态单质，则其标准摩尔生成焓为零）。 - **根据标准摩尔燃烧焓计算（定温定压过程）**：反应的标准摩尔焓变等于反应物的标准摩尔燃烧焓之和减去产物的标准摩尔燃烧焓之和，即\(\Delta_{r}H_{m}=\sum\Delta_{c}H_{m}\)（总反应物）\(-\sum\Delta_{c}H_{m}\)（总生成物）（参考状态单质只适用于标准摩尔生成焓，其标准摩尔燃烧焓不为零）。 - **根据化学键的键能计算**：化学反应中的反应热\(\Delta H=\)反应物的总键能 - 生成物的总键能;也可以根据\(\Delta H=\)生成物的总能量 - 反应物的总能量计算。 - **根据热化学方程式计算**：热化学方程式中反应热数值与各物质的化学计量数成正比。例如已知生成一定量某物质的反应热，可根据化学计量数比例关系计算其他量对应的反应热。 点击前往免费阅读更多精彩小说
What are the questions about the calculation of the heat of chemical reaction?
以下是一些关于化学反应热计算的题目类型： **一、根据键能计算反应热** 1. 例如已知反应方程式中各物质所含化学键的键能，通过公式\(\Delta H=\)反应物的键能总和\(-\)生成物的键能总和来计算反应热。像给出\(H-H\)、\(O = O\)和\(O-H\)键的键能，以及反应\(C(s)+H_{2}O(g)=CO(g)+H_{2}(g)\)，让求反应热\(\Delta H\)的值。 **二、根据反应物和生成物的总能量计算反应热** 1. 利用公式\(\Delta H = E\)（生成物）\(-E\)（反应物）。例如给出反应物和生成物的能量数值，计算反应是吸热还是放热以及\(\Delta H\)的具体数值。 **三、根据图像计算反应热** 1. 对于放热反应，\(\Delta H=(E_{2}-E_{1})kJ/mol=(a - b)kJ/mol=-c kJ/mol\);对于吸热反应，\(\Delta H=(E_{2}-E_{1})kJ/mol=(a - b)kJ/mol=+c kJ/mol\)。题目可能会给出反应的能量图像，要求根据图像确定反应热\(\Delta H\)的值，或者判断反应是吸热还是放热。 **四、热化学方程式相关的反应热计算** 1. 已知某个热化学方程式及其\(\Delta H\)，对热化学方程式进行左右颠倒同时改变正负号，或者各物质的化学计量数及其\(\Delta H\)的数值同时扩大或者缩小相同的倍数后，计算新反应的反应热。例如已知\(N_{2}(g)+3H_{2}(g)\rightleftharpoons2NH_{3}(g)\ \Delta H = - 92.2kJ/mol\)，求\(2NH_{3}(g)\rightleftharpoons N_{2}(g)+3H_{2}(g)\)的\(\Delta H_{1}\)以及\(\frac{1}{2}N_{2}(g)+\frac{3}{2}H_{2}(g)\rightleftharpoons NH_{3}(g)\)的\(\Delta H_{2}\)。 **五、根据燃烧热计算反应热** 1. 利用公式：可燃物完全燃烧产生的热量\(=\)可燃物的物质的量\(\times\)其燃烧热。例如已知乙醇的燃烧热是\(1366.8kJ/mol\)，求乙醇燃烧生成\(1mol\)液态水时放出的热量。 **六、根据中和热计算反应热** 1. 利用公式：中和反应放出的热量\(=n(H_{2}O)\times|\Delta H|\)。例如向\(1L 0.5mol/L\)的\(NaOH\)溶液中加入稀醋酸、稀盐酸、浓硫酸等物质，恰好完全反应时，比较对应的热效应\(\Delta H_{1}\)、\(\Delta H_{2}\)、\(\Delta H_{3}\)的大小关系。 **七、根据盖斯定律计算反应热** 1. 将两个或者两个以上的热化学方程式（包括\(\Delta H\)）相加或者相减（很多时候，在热化学方程式相加或相减之前需要乘以或者除以一个数），得到一个新的热化学方程式，从而计算反应热。例如给出多个热化学方程式，通过盖斯定律计算由特定反应物生成特定生成物的反应热。 2. 还会有一些综合题目，例如在一个反应体系中有多个反应同时发生，通过各反应的反应热以及物质之间的转化关系，计算某个反应的反应热或者某种物质的生成量等。 <a href="/?from=ask_words" style="color:red" target="_blank">点击前往免费阅读更多精彩小说</a>
reaction heat exchange
The reaction heat exchange was also known as the heat exchange reactor, and its structure was mostly similar to the shell-and-tube heat exchange. The catalyst could be placed in the tube or between the tubes, but it was rare to place it between the tubes. In a heat-exchange fixed-bed reactor, the gas flows from the top of the reactor down into the catalyst bed and flows out at the bottom. In actual production, this top-down flow method is mostly used. For the heat-exchange tube reactor, the reasonable choice of heat carrier was the key to control the reaction temperature and maintain the stable operating conditions of the reactor. The temperature difference between the heat carrier and the reaction temperature of the bed should be small, but it must be able to take away the heat released by the reaction. This required a large heat transfer coefficient under the condition of a certain heat transfer area. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Does the decomposition reaction release heat and the combination reaction absorb heat?
Most of the chemical reactions were exothermic, because the chemical reaction was a bond formation process, and the bond formation process was exothermic. However, there were also some chemical reactions that were xenothermic, such as C + CO2 = 2CO2. Most of the decomposition reactions were heat-absorbing reactions because the process of the decomposition reaction was a bond breaking process, and the bond breaking process was an heat-absorbing process. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
The relationship between reaction heat and heat release
The heat of reaction refers to the heat released or absorbed by a chemical reaction under constant pressure and without any non-expansion work. If the temperature of the product returns to the initial temperature of the reagent, the system will release or absorb heat. When the heat of reaction is less than 0, it is an exhalation process, that is, the value of the heat of reaction is equal to the amount of heat released (at this time, the amount of heat released is positive); when the heat of reaction is greater than 0, it is an absorption process. At this time, the reaction absorbs heat instead of releasing heat. In short, the heat of the reaction was a representation of the amount of heat released (the values were equal, but the signs were opposite). <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
supersonic heat reaction equipment
The working principle of the ultrasonic heating reaction equipment was that the energy-gathering ultrasonic horn was directly immersed in the reaction liquid of the reaction kettle, and a large amount of energy was directly transmitted to the reaction medium, effectively transforming the electrical energy into mechanical energy or ultrasonic energy. The ultrasonic energy could be controlled by changing the amplitude of the ultrasonic wave transmitted to the probe through the ultrasonic generator. For example, the Voshin - 1200 UIG high-pressure and high-temperature ultrasonic reactor was commonly used in laboratory extraction and chemical reaction research. It solved the problem of sealing the horn and the reactor. It could also be equipped with various chemical reactor accessories at high temperatures to achieve the reaction system atmosphere isolation and vapor condensation. There were also related ultrasonic heating machines available on the market. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Heat Reaction of Iodide and Amylum
Based on context alone At room temperature, there was no reaction between potassium iodate (Ki) and starch. However, if the mixture of potassium iodate and starch was heated under acidic conditions, a reaction would occur. Under acidic conditions, the ion equation of the potassium iodate is: 4I +4H + O 2 = 2I 2 + 2H 2 O. Iodine (I <2>) could turn the starch blue because it was embedded in the gaps of the starch's spiral structure, forming a blue clathrate. In general, the essence of the heating reaction between potassium iodate and starch was that the potassium iodate was first oxided to produce iodate, and then the iodate reacted with the starch. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Heat Reaction of Dibasic Acid
Oxalic acid was a dibasic acid. The two groups of the acid could be decarboxylated at a lower temperature to form formated acid and CO2. At a higher temperature, formated acid would undergo a dehydration reaction to form CO2 and water. The reaction equation was as follows: At lower temperatures: <<<p>></p>H - COOH + CO_2↑\); At higher temperatures: <br><br><br>> br><br>> br></br>>CO_2↑+ CO↑+ H_2O\)。 After the dibasic acid was heated, due to the different positions of the two carboxy groups, different chemical reactions such as water loss, loss of esh, or loss of esh at the same time would occur. At 300 ° C, the substituted dibasic acid could also undergo the above reactions. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Solar heat, physical reaction
The physical reaction of the sun's heat is nuclear fusion. In the high-temperature and high-pressure environment inside the sun, under extremely high temperature and pressure, the electrons outside the nucleus were freed from the constraints of the nucleus, and the nuclei attracted each other and collided with each other. To be specific, it was a reaction where four hydrogen atoms fused into one helium atom. This process would release a huge amount of energy, which was the principle of the sun's heat. According to the mass-energy equation E = MC2, the sun could emit a steady stream of light and heat by losing a little mass in this process. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Is the weak acid reaction heat-absorbing or heat-releasing?
It was too general to say that the weak acid reaction was either heat absorbing or heat releasing. For example, the weak acid's ionisation process was heat absorbing. This was because the weak acid needed to overcome the effect of chemical bonds to absorb energy when it was ionised. However, if a weak acid is involved in the neutralizing reaction, since the weak acid is not completely ionised, it absorbs heat during the neutralizing reaction at the same time. Therefore, the heat released by the neutralizing reaction of the weak acid and the strong base (or strong acid) is less than the neutralizing heat of the strong acid and strong base neutralizing reaction.(The neutralizing reaction of a diluted solution of a strong acid and base: H+(aq)+Oh-(aq) H2O(l); AH = -57.3kJ/mole), but the whole reaction was still an exothermic reaction, but the heat released was less than that of a strong acid and base neutralizing reaction. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
The difference and connection between reaction heat and combustion heat
The heat of reaction refers to the heat released or absorbed by the system when the temperature of the product returns to the initial temperature of the reagent after the chemical reaction occurs under constant pressure and without non-expansion work. It is the heat released or absorbed by the system when the chemical change occurs in the process of constant temperature and constant pressure. The heat of combustion is the heat released when 1 mole of pure substance is completely burned to form a specified product at 101 kPa. The difference between the two was: 1. The heat of reaction was a broader concept, covering the heat changes in various chemical reactions, while the heat of combustion was specific to the reaction of complete combustion of matter and oxygen. 2. The heat of reaction occurs under the conditions of constant temperature, constant pressure, and no non-expansion work. The heat of combustion is clearly defined as the heat of complete combustion of 1 mole of pure substance under 101 kPa. 3. The calculation of the heat of reaction is related to the type of reaction, the amount of substance, and the degree of reaction. The heat of combustion is only the heat of the complete combustion of 1 mole of pure substance to produce a specified product. The connection between the two was that the heat of combustion was a special form of reaction heat. The measurement of the heat of combustion could help to calculate the heat of formation of a compound, the heat of reaction of a chemical reaction, and the bond energy. The data of the heat of combustion could provide a basis for the calculation and research of the heat of reaction. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>