NaOH 同埋 NaCl 邊個 Boiling Point/ Melting Point 高 D?

Sodium chloride (m.p. 801oC / b.p. 1465oC) has a higher melting point and a higher boiling point than sodium hydroxide (m.p. 318oC / b.p. 1390oC).

Both sodium chloride and sodium hydroxide are ionic compounds. Although the hydroxide ion is formed by linking an O atom and an H atom together by covalent bonds, sodium hydroxide is found to be having giant ionic structure which consisting a huge number of Na+ and OH- ions. Besides, the O-H covalent bonds in OH- ions would not be broken during melting or boiling.

In NaCl, Na+ and Cl- ions are held together by electrostatic forces. Similarly, in NaOH, the Na+ and OH- ions are held together by electrostatic forces. Since Cl- ion is smaller in size than OH- , the Na+-Cl- distance in NaCl is shorter than the Na+- OH- distance in NaOH. Therefore, the ionic bonds in NaCl are stronger than those in NaOH. Conclusively, NaCl has a higher melting point and a higher boiling point than NaOH.

請問點解說 Cl- ion is smaller in size than OH-
cl不是有大d的relative atomic mass 嗎?

還有mg2cl 同nacl 比哪個boiling pt 較大?

sodium chloride has higher boiling point and melting point
than sodium hydroxide. the ionic bond between sodium ion
and chloride ion is stronger. so more energy is needed to break
the bond.