2.19 describe the reactions of magnesium, carbon and sulfur with oxygen in air, and the acid-base character of the oxides produced

Oxygen is a reactive gas.
Any substance that burns in air will burn more brightly and more vigorously with oxygen. 

Magnesium burns with bright, white flame to form a white powder.

Carbon burns with a yellow-orange flame to form a colourless gas, CO2.

Sulfur burns with a blue flame to form a colourless gas.