alevel化学中两个比较容易混淆的概念：
       Standard enthalpy change of hydration n. 标准水和焓变
     The standard enthalpy change of hydration is the enthalpy change when one mole of a gaseous ion dissolves in water to give an infinitely dilute solution . 
       标准水和焓变是1 mol气态离子溶入水形成稀溶液所放出的能量。
           Na+ (g) +aq → Na+ (aq) ; ΔHΘhydrogen=-406 kJ mol-1
       Standard enthalpy change of solution n. 标准溶解焓变 
     The standard enthalpy change of solution is the enthalpy change when one mole of a solute dissolves in a solvent to give an infinitely dilute solution. 
         NaCl (s) +aq→ NaCl (aq); ΔHΘsolution= +1 kJ mol-1
       标准水和焓变是1 mol溶质溶于溶剂后形成稀溶液所放出的能量。
     这两种焓变的区别是可溶物质的种类，前一种必须是气态离子，后一种是任意一种溶剂。