The correct option is Magnesium oxide.
Explanation
The question pertains to the chemical properties of metals, specifically the combustion reaction of magnesium in the presence of atmospheric oxygen. This is a classic example of a combination reaction.Detailed Analysis
- Reaction Process: Magnesium is a reactive metal. When a magnesium ribbon is burnt in air, it reacts chemically with the oxygen present in the atmosphere.
- Observation: The reaction is highly exothermic and is characterized by the emission of a dazzling white flame.
- Product Formation: The magnesium atoms combine with oxygen atoms to form a new compound, Magnesium oxide (MgO). This substance appears as a white powder or ash.
- Chemical Equation: The balanced chemical equation for this reaction is:
2Mg (s) + O2 (g) → 2MgO (s) - Elimination of Other Options:
- Magnesium hydroxide [Mg(OH)2]: This is formed when magnesium oxide is dissolved in water, not directly from burning in air.
- Magnesium carbonate [MgCO3]: This would require a reaction with carbon dioxide. While a dull coating of carbonate may form on magnesium kept in air over time, the white powder from burning is the oxide.
- Magnesium chloride [MgCl2]: This forms when magnesium reacts with chlorine gas or hydrochloric acid.
Key Takeaway
The burning of magnesium ribbon in air is an oxidation reaction that produces magnesium oxide, a white powder.