Question

The old camera flash bulb used Mg metal sealed in a bulb with oxygen. At 25°C, the reaction is:

Mg(s) + ¹/²O₂(a) → MgO₍ₛ₎
∆S (J/K.mol): Mg=32.7; O₂=205.0; MgO=26.9
∆H (kJ/mol: Mg=0; O₂=0; MgO=-601.2

Answer 1

Magnesium reacts with oxygen in a combination reaction to form magnesium oxide. The reaction is exothermic and produces heat and light. This chemical change can be identified by the formation of a crumbly white powder and the evolution of a bright white flame.

Step-by-step explanation:

When magnesium reacts with oxygen, it undergoes a combination reaction to form magnesium oxide. The balanced chemical equation for this reaction is: 2Mg (s) + O₂(g) → 2MgO (s).

During the reaction, two magnesium atoms combine with one molecule of oxygen gas to produce two units of magnesium oxide. The reaction is exothermic, meaning heat is evolved during the process. Additionally, the reaction is highly reactive and produces a bright white flame and a crumbly white powder of MgO.

The reaction between magnesium and oxygen is an example of a chemical change, which can often be identified by the evolution of heat or light, the formation of new substances, or the change in color. Magnesium's reactivity with oxygen makes it useful in various applications such as flares, fireworks, and as a component in camera flash bulbs.