ΔH 焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV)

使用说明与常见问题How-to & FAQ

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」是什么？What is the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) tool?

三种方法计算焓变：按标准生成焓 ΔH = ΣΔHf(产物) − ΣΔHf(反应物)（每行“系数 生成焓”），按热量 q = m·c·ΔT，或按 ΔH = ΔU + PΔV。可选 J、kJ、cal、kcal，并判断放热、吸热或热中性。本地处理。Enthalpy change three ways: from standard enthalpies of formation, ΔH = ΣΔHf(products) − ΣΔHf(reactants) (one "coefficient value" per line), from heat q = m·c·ΔT, or from ΔH = ΔU + PΔV. Choose J, kJ, cal or kcal; the page says whether the change is exothermic, endothermic or thermoneutral. Processed locally.

如何使用「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」？How do I use the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) tool?

在「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」中，填写「方法」、「质量 m（g）」、「比热容 c（J/(g·°C)）」、「温度变化 ΔT（°C 或 K）」、「内能变化 ΔU（kJ）」等参数，结果会随输入实时计算并显示在下方。In the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV): Fill in "Method", "Mass m (g)", "Specific heat c (J/(g·°C))", "Temperature change ΔT (°C or K)", "Internal energy change ΔU (kJ)"; results are recalculated instantly as you type.

按生成焓怎么算？How does the formation method work?

ΔH° = Σ(系数 × ΔHf°)产物 − Σ(系数 × ΔHf°)反应物，每行写“系数 生成焓（kJ/mol）”。例如甲烷燃烧 CH₄ + 2O₂ → CO₂ + 2H₂O(l)：产物 1 × (−393.5) + 2 × (−285.8)，反应物 1 × (−74.8) + 2 × 0，ΔH° = −890.3 kJ/mol，放热。单质（如 O₂）的标准生成焓为 0。ΔH° = Σ(coefficient × ΔHf°) of the products − Σ(coefficient × ΔHf°) of the reactants, with one line per substance: coefficient and ΔHf in kJ/mol. For methane combustion CH₄ + 2O₂ → CO₂ + 2H₂O(l): products 1 × (−393.5) + 2 × (−285.8), reactants 1 × (−74.8) + 2 × 0, so ΔH° = −890.3 kJ/mol, exothermic. Elements in their standard state, such as O₂, have ΔHf° = 0.

q = mcΔT 是什么？What is q = mcΔT?

物质吸收的热量 q = 质量 × 比热容 × 温度变化，例如 100 g 水（c = 4.184 J/(g·°C)）升温 10 °C 吸收 4,184 J = 4.184 kJ。恒压下这部分热量就是 ΔH。The heat a substance absorbs: q = mass × specific heat × temperature change, so 100 g of water (c = 4.184 J/(g·°C)) warming by 10 °C absorbs 4,184 J = 4.184 kJ. At constant pressure that heat is ΔH.

ΔH = ΔU + PΔV 的单位？What units does ΔH = ΔU + PΔV use?

ΔU 按 kJ，P 按 kPa，ΔV 按 L；1 kPa·L = 1 J，所以 PΔV(kJ) = P × ΔV ÷ 1000。ΔU in kJ, P in kPa and ΔV in L; 1 kPa·L = 1 J, so PΔV in kJ = P × ΔV ÷ 1000.

什么是热中性？What does thermoneutral mean?

ΔH = 0 时既不放热也不吸热，页面显示“热中性”；判断前会把 10⁻⁹ 以下的浮点误差视为 0，例如 0.1 + 0.2 − 0.3 判为 0。When ΔH = 0 the change neither releases nor absorbs heat, and the page says thermoneutral; floating-point noise below 10⁻⁹ is treated as 0 first, so 0.1 + 0.2 − 0.3 counts as 0.

能举个计算实例吗？Can you show a worked example?

例如在「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」中填 方法 = 标准生成焓，产物（每行：系数 ΔHf kJ/mol） = 1 -393.5（换行）2 -285.8，反应物（每行：系数 ΔHf kJ/mol） = 1 -74.8（换行）2 0，质量 m（g） = 100，比热容 c（J/(g·°C)） = 4.184，温度变化 ΔT（°C 或 K） = 10，结果区显示：ΣΔHf(产物)：-965.1 kJ；ΣΔHf(反应物)：-74.8 kJ；ΔH°：-890.3 kJ（每摩尔反应）；类型：放热（ΔH < 0）For example, entering Method = Enthalpies of formation, Products (each line: coefficient ΔHf in kJ/mol) = 1 -393.5 (new line) 2 -285.8, Reactants (each line: coefficient ΔHf in kJ/mol) = 1 -74.8 (new line) 2 0, Mass m (g) = 100, Specific heat c (J/(g·°C)) = 4.184, Temperature change ΔT (°C or K) = 10 in the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) gives: ΣΔHf(products): -965.1 kJ; ΣΔHf(reactants): -74.8 kJ; ΔH°: -890.3 kJ (per mole of reaction); Type: Exothermic (ΔH < 0)

哪些输入会被检查？Which inputs are validated?

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」会检查这些输入——「质量 m（g）」、「比热容 c（J/(g·°C)）」：必须填写，须大于 0；「温度变化 ΔT（°C 或 K）」、「内能变化 ΔU（kJ）」：所选方式用到时必须填写；「压强 P（kPa）」：不能为负数；「体积变化 ΔV（L）」：可留空；绝对值超过 10¹⁵ 的数也会被拒绝。不符合时结果区显示具体提示，不会给出数字。The Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) checks its inputs — "Mass m (g)", "Specific heat c (J/(g·°C))": required, must be greater than 0; "Temperature change ΔT (°C or K)", "Internal energy change ΔU (kJ)": required when the chosen option uses it; "Pressure P (kPa)": cannot be negative; "Volume change ΔV (L)": optional; numbers above 10¹⁵ in absolute value are rejected too. When a value fails, the result area names the problem instead of showing a number.

有哪些选项可以调整？What options can I adjust?

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」的设置：「方法」可选 标准生成焓、热量 q = m·c·ΔT、ΔH = ΔU + PΔV / ΔH = ΔU + PΔV（默认 标准生成焓）；「质量 m（g）」默认 100；「比热容 c（J/(g·°C)）」默认 4.184；「温度变化 ΔT（°C 或 K）」默认 10；「内能变化 ΔU（kJ）」默认 -50；「压强 P（kPa）」默认 101.325；「体积变化 ΔV（L）」默认 2；「结果单位」可选 kJ / kJ、J / J、kcal / kcal、cal / cal（默认 kJ / kJ）。每次生成结果都按当前设置处理。Settings in the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) — "Method": Enthalpies of formation, Heat q = m·c·ΔT, ΔH = ΔU + PΔV / ΔH = ΔU + PΔV (default Enthalpies of formation); "Mass m (g)" default 100; "Specific heat c (J/(g·°C))" default 4.184; "Temperature change ΔT (°C or K)" default 10; "Internal energy change ΔU (kJ)" default -50; "Pressure P (kPa)" default 101.325; "Volume change ΔV (L)" default 2; "Result unit": kJ / kJ, J / J, kcal / kcal, cal / cal (default kJ / kJ). The result…

计算结果可以用于作业或工程吗？Can I use the results for homework or engineering?

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」使用教科书标准公式（公式写在说明和常见问题中），适合学习和估算核对；涉及安全的工程设计请以规范和实测为准。The Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) uses standard textbook formulas (given in the description and FAQ), which is good for learning and checking estimates; for safety-critical engineering follow codes and measured values.

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」免费吗？需要注册吗？Is the Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) free? Do I need an account?

「焓变计算器（生成焓、q = mcΔT、ΔH = ΔU + PΔV）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Enthalpy Change Calculator (Formation, q = mcΔT, ΔH = ΔU + PΔV) is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.