Practice MCQ Questions and answers on Chemistry-GK

Bleaching powder, CaOCl₂ or calciumoxychloride is used to kill germs and bacteria of water because it contains chlorine element, which is good disinfecting agent.

Softening is the process of removing the dissolved calcium and magnesium salts that cause hardness in water. Water softening is achieved either by adding chemicals that form insoluble precipitates or by ion exchange.

Hard water and soft water can be distinguished by using detergent.

Soap solution is used to measure the hardness of rain water, temporarily hard water and sea-water. Hard water does not form soap lather. This is because magnesium ions or calcium ions present in hard water react with soap to form calcium stearate or magnesium stearate and thus forms scum.

The purest form of water is rain water.

Water cycle, also called hydrologic cycle, cycle that involves the continuous circulation of water in the Earth-atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation, transpiration, condensation, precipitation, and runoff. Although the total amount of water within the cycle remains essentially constant, its distribution among the various processes is continually changing.

Hardness can be removed by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column.

Acid rain is caused by a chemical reaction that begins when compounds like sulphur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

Sulphur dioxide (SO₂) and Nitrogen oxides (NO_x) are responsible for acid rain.

Power plants release the majority of sulphur dioxide and much of the nitrogen oxides when they burn fossil fuels, such as coal, to produce electricity. In addition, the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause acid rain.