Question

1. na2o(s) + h2o(ℓ) → naoh(aq) → na+(aq) + oh−(aq) 13. k2o(s) + h2o(ℓ) → koh → k+ 14. mgo(s) + h2o(ℓ) → mg(oh)2 → mg2+ 15. cao(s) + h2o(ℓ) → ca(oh)2 → ca2+ d. soluble metal oxides react with water to form hydroxides which dissociate in solution

Explanation:

Step1: Recall metal - oxide reactions

Soluble metal oxides react with water to form metal hydroxides. The general reaction is \(MO + H_2O
ightarrow M(OH)_2\) for divalent metals (\(M^{2 +}\)) and \(M_2O+H_2O
ightarrow 2MOH\) for monovalent metals (\(M^{+}\)).

Step2: Analyze given reactions

• For \(Na_2O(s)+H_2O(l)

ightarrow 2NaOH(aq)\), \(NaOH\) dissociates into \(Na^{+}(aq)\) and \(OH^{-}(aq)\) in solution.

• For \(K_2O(s)+H_2O(l)

ightarrow 2KOH(aq)\), \(KOH\) dissociates into \(K^{+}(aq)\) and \(OH^{-}(aq)\) in solution.

• For \(CaO(s)+H_2O(l)

ightarrow Ca(OH)_2\). Although \(Ca(OH)_2\) is less soluble than \(NaOH\) and \(KOH\), it still dissociates into \(Ca^{2 +}(aq)\) and \(2OH^{-}(aq)\) in the solution it forms.

• For \(MgO(s)+H_2O(l)\), \(MgO\) is insoluble in water and does not react readily with water to form a soluble hydroxide in significant amounts under normal conditions.

Answer:

1. \(Na_2O(s)+H_2O(l)

ightarrow NaOH(aq)\), \(NaOH(aq)
ightarrow Na^{+}(aq)+OH^{-}(aq)\)

1. \(K_2O(s)+H_2O(l)

ightarrow KOH(aq)\), \(KOH(aq)
ightarrow K^{+}(aq)+OH^{-}(aq)\)

1. \(MgO(s)+H_2O(l)\) - \(MgO\) is insoluble and does not react to form a soluble hydroxide easily.
2. \(CaO(s)+H_2O(l)

ightarrow Ca(OH)_2\), \(Ca(OH)_2
ightarrow Ca^{2 +}(aq)+2OH^{-}(aq)\)