Question

Magnesium continues to burn in nitric oxide, while burning of sulphur is extinguished. Why?

Answer 1

The heat that is evolved by the burning of magnesium (Mg) is quite sufficient to decompose nitric oxide (NO) into nitrogen $\left( {{N_2}} \right)$ and oxygen $\left( {{O_2}} \right)$. Thus, the oxygen that is obtained supports combustion, but the burning of sulphur does not decompose nitric oxide and hence it is extinguished.

Complete step by step answer:
Magnesium is a metal. It acts as a strong reducing agent with each atom of Mg losing its two outermost electrons thus forming $M{g^{2 + }}$ ions. Therefore, it is able to reduce nitric oxide (NO) to $M{g_3}{N_2}$​. The reaction between magnesium and oxygen is highly exothermic i.e. heat that is evolved during burning of Mg is enough to break down of Nitric oxide (NO) into Nitrogen $\left( {{N_2}} \right)$ and Oxygen $\left( {{O_2}} \right)$. Oxygen​ allows combustion or burning and thus helps the burning of Magnesium to continue.
While sulphur is a non-metal. It acts as an oxidizing agent. It does not conduct heat and electricity because unlike metals, it does not have free electrons. In contrast to Mg, the heat evolved during the burning of sulphur is not sufficient to decompose NO to $\left( {{N_2}} \right)$ and $\left( {{O_2}} \right)$​. As a result, sulphur stops burning in NO.
Hence, the magnesium (Mg) continues to burn in NO, but the burning Sulphur (S) is extinguished

Note: Magnesium (Mg) and sulphur (S), both need oxygen for burning to occur and continue and the amount of oxygen that is available determines whether the burning will continue or be extinguished. Dropping burning magnesium or sulphur into a jar causes oxygen to become a limiting factor in the combustion reactions.