# 化学反応式

## 概要

 反応物 ${\displaystyle {\ce {->}}}$  生成物

### 具体例

• ${\displaystyle {\ce {HCl}}}$ 塩酸
• ${\displaystyle {\ce {NaOH}}}$ 水酸化ナトリウム

が化学反応して生成物である

• ${\displaystyle {\ce {H2O}}}$ 水分子
• ${\displaystyle {\ce {NaCl}}}$ 食塩

ができあがる状況を示した化学反応式は

 ${\displaystyle {\ce {HCl + NaOH -> H2O + NaCl}}}$

と表記される。

### 一般的な記号

• 「=」- 化学量論的関係を示すために使用される
• 「→」- 正順方向反応を示すために使用される
• 「⇄」 - 両方向の反応を示すために使用される[2]
• ${\displaystyle {\ce {<=>}}}$ 」 - 平衡を示すために使用される[3]

 ${\displaystyle {\ce {NH3 + H2O <=> NH4^+ + OH^-}}}$

### 化学式に付加する記号

• （s） - 固体
• （l） - 液体
• （g） - 気体
• （aq） - 水溶液を示す

## 化学量論的反応式

${\displaystyle {\ce {2CuO + C -> 2Cu + CO2}}}$

と表される。

## 脚注

1. ^ Crosland, M.P. (1959). “The use of diagrams as chemical 'equations' in the lectures of William Cullen and Joseph Black”. Annals of Science 15 (2): 75–90. doi:10.1080/00033795900200088.
2. ^ The notation ${\displaystyle \rightleftarrows }$  was proposed in 1884 by the Dutch chemist Jacobus Henricus van 't Hoff. See: van 't Hoff, J.H. (1884) (フランス語). Études de Dynamique Chemique. Amsterdam, Netherlands: Frederik Muller & Co.. pp. 4–5  Van 't Hoff called reactions that didn't proceed to completion "limited reactions". From pp. 4–5: "Or M. Pfaundler a relié ces deux phénomênes … s'accomplit en même temps dans deux sens opposés." (Now Mr. Pfaundler has joined these two phenomena in a single concept by considering the observed limit as the result of two opposing reactions, driving the one in the example cited to the formation of sea salt [i.e., NaCl] and nitric acid, [and] the other to hydrochloric acid and sodium nitrate. This consideration, which experiment validates, justifies the expression "chemical equilibrium", which is used to characterize the final state of limited reactions. I would propose to translate this expression by the following symbol: HCl + NO3 Na ${\displaystyle \rightleftarrows }$  NO3 H + Cl Na. I thus replace, in this case, the = sign in the chemical equation by the sign ${\displaystyle \rightleftarrows }$ , which in reality doesn't express just equality but shows also the direction of the reaction. This clearly expresses that a chemical action occurs simultaneously in two opposing directions.)
3. ^ The notation ${\displaystyle {\ce {<=>}}}$  was suggested by Hugh Marshall in 1902. See: Marshall, Hugh (1902). “Suggested Modifications of the Sign of Equality for Use in Chemical Notation”. Proceedings of the Royal Society of Edinburgh 24: 85–87. doi:10.1017/S0370164600007720.
4. ^ The symbol is more properly denoted as a simple triangle (△), which was originally the alchemical symbol for fire.
5. ^ This symbol comes from the Planck equation for the energy of a photon, ${\displaystyle E=h\nu }$ . It is sometimes mistakenly written with a 'v' ("vee") instead of the Greek letter '${\displaystyle \nu }$ ' ("nu")

## 外部リンク

• 西川友成「化学反応式(<特集>現代化学の神話)」『化学教育』第15巻第1号、日本化学会、1967年、 18-25頁、 doi:10.20665/kagakukyouiku.15.1_18NAID 110001821160