7.5.1 Periodic Trends

Section A

Section B

1. Magnesium burns in oxygen to form magnesium oxide which melts at 2800 ^oC.

(a) (i) State the type of bonding in magnesium oxide.

[1]

(ii) Suggest why magnesium oxide has such a high melting point.

[2]

(b) Magnesium oxide dissolves only slightly in water , but enough for the solution to turn litmus blue.

MgO + H₂O Mg²⁺ + 2OH^-

(i) Using the BrØnsted-Lowry theory explain why the solution is alkaline.

[2]

(ii) Calculate the pH of the solution produced when 0.0006 g of magnesium oxide is dissolved in 100 cm³ of water.

[4]

(j) Compare the type of bonding and behaviour with water of aluminium oxide, sulphur dioxide and chlorine(VII) oxide.

[6]