Seawater is salty because rainwater dissolves the salt minerals found in soil and rocks as it travels through rivers and streams en route to the sea The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid. The rain physically erodes the rock and the acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers and then to the ocean which makes them salty.

Correct Option: C

Seawater is salty because rainwater dissolves the salt minerals found in soil and rocks as it travels through rivers and streams en route to the sea The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid. The rain physically erodes the rock and the acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers and then to the ocean which makes them salty.

The allotropic form of Phosphorus (white phosphorus) is less stable and therefore highly reactive because of angular strain in P₄ molecule where the angles are only 60o. Having very low ignition temperature, it readily catches fire in air to give dense white fumes of P₄O₁₀. So it is kept in water to avoid oxidation by the oxygen present in air.

Correct Option: B

The allotropic form of Phosphorus (white phosphorus) is less stable and therefore highly reactive because of angular strain in P₄ molecule where the angles are only 60o. Having very low ignition temperature, it readily catches fire in air to give dense white fumes of P₄O₁₀. So it is kept in water to avoid oxidation by the oxygen present in air.

Chlorofluorocarbons (CFCs), also known as Freon, cause the breakdown of the ozone layer that protects the earth from the sun’s ultraviolet (UV) radiation.In the upper atmosphere, the UV-induced breakdown of CFCs releases free, highly reactive chlorine and bromine atoms that lead to the breakdown of the stratospheric ozone layer. Owing to ozone depletion in the upper atmosphere, CFCs have been phased out under the Montreal Protocol of 1987.

Correct Option: C

Chlorofluorocarbons (CFCs), also known as Freon, cause the breakdown of the ozone layer that protects the earth from the sun’s ultraviolet (UV) radiation.In the upper atmosphere, the UV-induced breakdown of CFCs releases free, highly reactive chlorine and bromine atoms that lead to the breakdown of the stratospheric ozone layer. Owing to ozone depletion in the upper atmosphere, CFCs have been phased out under the Montreal Protocol of 1987.

Quartz is a compound of one part silicon and two parts of oxygen, silicon dioxide, SiO₂. Quartz is the most abundant silica mineral. It is used in a number of industries, the important being glass, foundry, sodium silicate, silicon alloys, etc. The various grades of sodium silicate are characterized by their SiO₂:Na₂O weight ratio.

Correct Option: D

Quartz is a compound of one part silicon and two parts of oxygen, silicon dioxide, SiO₂. Quartz is the most abundant silica mineral. It is used in a number of industries, the important being glass, foundry, sodium silicate, silicon alloys, etc. The various grades of sodium silicate are characterized by their SiO₂:Na₂O weight ratio.

Fire extinguishers use carbon dioxide to displace the oxygen necessary for a fire to burn, extinguishing the blaze. Fires need oxygen, fuel, and heat to ignite, and removing any one of those three components can put out a fire. It is useful for electrical fires and some flammable liquid fires, but may make some gasoline or paper fires worse by dispersing burning material.

Correct Option: C

Fire extinguishers use carbon dioxide to displace the oxygen necessary for a fire to burn, extinguishing the blaze. Fires need oxygen, fuel, and heat to ignite, and removing any one of those three components can put out a fire. It is useful for electrical fires and some flammable liquid fires, but may make some gasoline or paper fires worse by dispersing burning material.