Sodium Oxide (Na₂O) and Water
* Reaction: Sodium oxide reacts vigorously with water to form sodium hydroxide (NaOH):
Na₂O + H₂O → 2NaOH
* NaOH is a strong base: Sodium hydroxide completely dissociates in water, releasing hydroxide ions (OH⁻) which make the solution highly alkaline, resulting in a high pH.
Calcium Oxide (CaO) and Water
* Reaction: Calcium oxide reacts with water to form calcium hydroxide (Ca(OH)₂):
CaO + H₂O → Ca(OH)₂
* Ca(OH)₂ is a strong base but less soluble: Calcium hydroxide is also a strong base, meaning it also releases hydroxide ions (OH⁻) into solution. However, it is less soluble in water than sodium hydroxide. This means that less Ca(OH)₂ dissolves, producing fewer OH⁻ ions compared to NaOH in a similar solution.
Why Sodium Oxide Solution has Higher pH
The higher pH of the sodium oxide solution is due to:
* Higher Concentration of OH⁻: Because sodium hydroxide is more soluble, it produces a higher concentration of hydroxide ions in solution, making the solution more alkaline.
* Stronger Base: Both sodium hydroxide and calcium hydroxide are strong bases, but their solubility difference significantly affects the hydroxide ion concentration.
In summary: Although both sodium oxide and calcium oxide react with water to form strong bases, the higher solubility of sodium hydroxide leads to a higher concentration of hydroxide ions, resulting in a higher pH compared to the calcium oxide solution.
