Question

Which one of the following results in the formation of a new chemical compound?
\[
  a.{\text{ burning phosphorus in air}} \\
  {\text{b}}{\text{. heating silver wire to 10}}{{\text{0}}^o}C \\
  c.{\text{ dissolving common salt in water}} \\
  {\text{d}}{\text{. melting ice}} \\
 \]

Answer 1

Hint: Phosphorus is a toxic substance, generally produced from rocks. Usually white phosphorus is used in industries to manufacture chemicals, which can be used in fertilizers, additives of food, pesticides,fireworks and in sanitization of places.

Complete answer:
Phosphorus on contact with air it spontaneously ignites and produces phosphorus oxides. These can also be identified by toxic fumes. Phosphorus also reacts violently with oxidants, metals, or halogens, which causes fire and explosion hazard. It can also react with bases present in air to give phosphine gas.it ignites at approximately \[{30^o}C\] in air and the temperature is higher when the air is dry. It burns rapidly and releases dense white fumes. It is used by the military as a smoke producing agent to mislead the enemy. Looking at the other options, silver wire does not give any effect under its melting point which is more than \[{\text{10}}{{\text{0}}^o}C\]. So no new chemical compound is formed by silver wire.
When salt is dissolved in water a homogeneous mixture is formed. The salt component dissociates in ionic form. Again there is no new compound formed. When we simply talk about melting of ice, the formula remains the same. Only its state and the energy changes.
Hence the answer will be burning of phosphorus with air.

Note:
White phosphorus burns in air and causes several burns when in contact with eyes and skin. The smoke produced by phosphorus causes eye and respiratory tract irritation.