Question

Rain is called acid rain when pH is below?
A. 7
B. 6.5
C. 6
D. 5.6

Answer 1

Hint: Acid precipitation/ acid deposition are synonyms of acid rain. The word acid rain was first used in 1852 by Scottish chemist Robert Angus Smith when he was investigating rainwater chemistry near industrial cities in England and Scotland.

Complete answer: Acid rain was recognized as a regional environmental issue which affects the large areas of western Europe and eastern North America. It also occurs in Asia and parts of Africa, South America, and Australia. However the problem of acid rain has been reduced in some areas, but it became an important environmental issue in major industrial and industrial agricultural regions worldwide. Acid rain means acid deposition, acidity can move from the atmosphere to Earth’s surface in many ways. It includes acidic rain as well as other forms of acidic wet deposition—such as snow, sleet, hail, and fog. Acid deposition also includes the dry deposition of acidic particles and gases, which can
affect landscapes during dry periods. Thus, acid deposition affects the landscapes and the living things
which are present within them. Acid deposition reduces the pH of surface waters and lowers biodiversity. It weakens the trees and increases their susceptibility to damage by various means such as drought, extreme cold, and pests. In acid-sensitive areas, acid rain also depletes the soil, it contributes to the corrosion of surfaces exposed to air pollution and is responsible for the deterioration of limestone and marble buildings and monuments. The pH scale measures the solution whether it is acidic or basic. Substances are considered acidic below a pH of 7. The rain is called acidic when its pH reaches below 6.0 because the pH of normal rain is 6−6.5. It is caused by the large-scale emission of acidic gases into the atmosphere from thermal power plants, industries and automobiles.
So the correct answer is option C

Note: Acid deposition also affects human-made structures. It affects the marble and limestone, which are common building materials found in many historic structures, monuments, and gravestones. The staining of the Taj Mahal is the best example of the effects of acid rain on marbles and
monuments.