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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Enthalpy of neutralization ： ウィキペディア英語版 Enthalpy of neutralization The enthalpy of neutralization (Δ''H''n) is the change in enthalpy that occurs when one equivalent of an acid and one equivalent of a base undergo a neutralization reaction to form water and a salt. It is a special case of the enthalpy of reaction. It is defined as the energy released with the formation of 1 mole of water. When a reaction is carried out under standard conditions at the temperature of 298 K (25 degrees Celsius) and 1 atm of pressure and one mole of water is formed it is called the ''standard enthalpy of neutralization'' (Δ''H''no). The energy (''Q'') released during a reaction is $Q\; =\; mc\_\; \backslash Delta\; T$ where ''m'' is the mass of the solution, ''cp'' is the specific heat capacity of the solution, and ∆''T'' is the temperature change observed during the reaction. From this, the standard enthalpy change (∆H) is obtained by division with the amount of substance (in moles) involved. $\backslash Delta\; H\; =\; -\; \backslash frac$ The standard enthalpy change of neutralization for a strong acid and base is -55.8 kJ/mol.〔 The standard enthalpy of neutralization〔(【引用サイトリンク】url=http://faculty.ccri.edu/aahughes/GenChemII/Lab%20Experiments/Enthalpy_of_Neutralization.pdf )〕 for organic acids is slightly less exothermic than that of mineral acids because of the partially ionizing property of weak organic acids. The bond between the proton and its conjugate base requires energy to be broken, hence the lower measured value enthalpy change. For weak acids and bases, heat of neutralization is different because they are not dissociated completely and during dissociation some heat is absorbed - total heat evolved during neutralization will be smaller. e.g. $HCN\; +\; NaOH\; \backslash rightarrow\; NaCN\; +\; H\_O;\; \backslash Delta\; H\; =\; -12\; kJ/mol$ Heat of ionization in this reaction is equal to (–12 + 57.3) kJ/mol = 45.3 kJ/mol == Enthalpy change of a reaction of neutralization an acid and a base == When a powerful acid and a powerful base react, enthalpy change is unique. It may be more clear in the example below, $NaOH\_\; +\; HCl\_\; \backslash rightarrow\; NaCl\_+H\_O\_$ when we consider the above reaction it is clear the only reaction we can see inside this is, $H^\_\; +\; OH^\_\; \backslash rightarrow\; H\_O\_$ Enthalpy change of this reaction is -57.7 kJ mol−1 When a weak acid reacts with a powerful base the enthalpy change must be a lesser enthalpy change than -55.8 kJ mol−1, as weak acids in solution do not fully dissociate to their respective anions and cations. To dissociate these bonds some amount of energy is needed; the enthalpy change reduces. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Enthalpy of neutralization」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.