Q. Why burning Mg continues to burn in NO, but burning sulphur is extinguished?
Ans. Magnesium being a metal acts as a strong reducing agent with each atom of Mg losing its two outermost electrons to form Mg2+ ions. Hence, it reduces nitric oxide (NO) to Mg3N2.
Heat evolved during burning of Mg is enough to decompose NO to N2 and O2. O2 thus produced keeps Mg burning.
On the other hand, sulphur, being a non-metal 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 produced during burning of sulphur is not sufficient to decompose NO to N2 and O2. As a result, sulphur stops burning in NO.