Question

which one of the following involve a chemical reaction ? a) evaporation of water
b) storing of nitrogen gas under pressure
c) keeping Petrol in China dish in open
d) heating magnesium wire in the presence of air at high temperature ​

Answer 1

Answer:

d) heating magnesium wire in the presence of air at high temperature

Answer 2

Answer:

Heating magnesium wire in the presence of air at high temperature involves a chemical reaction.

Explanation

• When one or more substances(elements or Compounds) undergo a chemical change, with the absorption or release of energy, so as to form one or more new products, then the change taking place collectively, is called chemical reaction.
• Evaporation of water is the change of state or physical reaction. Same goes with storing of nitrogen gas under pressure which leads to change of state of nitrogen,from gaseous state to liquid.
• Keeping Petrol in China dish in open is also an example of physical changes where Petrol will evaporate.
• When Magnesium wire is heated in the presence of air at high temperature , the product formed is magnesium oxide(MgO).

2Mg + O2 = 2MgO + Heat energy.

This is a chemical reaction as the new product magnesium oxide(MgO) is forming and heat energy is releasing.