Normal rain has a pH of 6 while acid rain has pH of 5. Why is it so harmful in terms of acidity?
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Rain (or other forms of precipitation) that is acidic can cause damage to the tissues of organisms. The outer coverings of animals can be damaged (imagine if you took a bath in water that was acidic), and plant tissues can be hurt as well. Acid precipitation has been linked to the deterioration of some lakes and forests. The acid can leach calcium, potassium, and other nutrients from the soil (these are nutrients that plants need to grow); the growth of plants can suffer as a result. When plants become weakened or die, many animals who rely on them for food or a home also suffer.
- Acid rain causes acidification of lakes and streams and contributes to the damage of trees.
- Acid rain can damage soil by destroying many vital substances and washing away the nutrients.
- Soils naturally contain small amounts of poisonous minerals such as mercury and aluminium.
- Normally these minerals do not cause serious problems, but when acid rain falls on the ground and the acidity of the soil increases, chemical reactions occur allowing the poisonous minerals to be taken up by the plant roots
- Famous buildings like the Statue of Liberty in New York, the Taj Mahal in India and St. Paul's Cathedral in London have all been damaged by this sort of acid rain.
The pH scale is actually a logarithmic scale. What this means is pH is the negative of the logarithm of the concentration of hydrogen ions in a substance. Essentially, the more hydrogen ions there are, the smaller the number (and more acidic) a substance becomes. The formula is
pH = -log [H+]
So, to answer your question, while a range of 0 to 14 sounds small, the difference between a 5 and a 6 on the pH scale is by a factor of 10.
5 is stronger than a 6 by a factor of 10!
Sulphuric acids and nitric acid are the two main acids, which then dissolve in the water in the atmosphere and fall to the ground as acid rain or may remain in the atmosphere in clouds and fogs. Acidification of environment is a man made phenomenon. The acid rain is in fact a cocktail of sulphuric acid and nitric acid. Acid rains are a great threat to environment. Acid rains create complex problems and their impacts are far reaching. They increase soil acidity, thus affecting land, flora and fauna, causing acidification of lakes and streams thus affecting aquatic life, and affects crop productivity and human health.
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