Subject Experts Solutions for Chapter: Air and Oxygen, Exercise 2: PRACTICE QUESTIONS (COMPETITION WING)

What is the role of water vapour in the formation of fog?

An inverted glass jar is placed over a burning candle. After a while, the candle is removed and the inverted glass jar is placed in a trough of water. What do you observe, and justify your explanation.

Acid formed as a result of lightning reaches the earth's surface through precipitation, thus contributing to the acid rain as well as to the growth of plants. Justify.

$\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ are four layers of atmosphere. $\mathrm{A}$ helps in long-distance radio communications. In layer $\mathrm{B}$, most of the weather phenomena take place. The pollutants released from air conditioners and aerosols deplete layer $\mathrm{D}$ which also gets depleted by nitrous oxide. Meteorites burn up in layer $\mathrm{C}$. Identify the layers $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ and arrange them in an increasing order of height from the surface of the earth.

The element $\mathrm{X}$ has only three shells in which the difference in number of electrons between the last shell and second-last shell is equal to number of electrons in the first shell. This element $\mathrm{X}$ burns in oxygen to produce compound $\mathrm{Y}$, which turns acidified potassium dichromate paper green. $\mathrm{Y}$ turns moist blue litmus paper red due to the formation of compound $\mathrm{Z}$. Identify $\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$.

Ozone present in the troposphere is a major pollutant. However, ozone formation in aqua purifiers makes drinking water pure and safe. Explain.

Carbon dioxide is used for extinguishing fire caused by petroleum products but not fires caused by metals like $\mathrm{Na}$ or $\mathrm{Mg}$. Explain.

Explain the principle behind the usage of electrical precipitators on industries and catalytic converters in automobiles for controlling air pollution.