What is the chemical rain formula

acid rain

Acid rain is precipitation that contains more acid than normal precipitation. In this post, we'll show you what acid rain is, what its effects are, and what countermeasures you can take.

Do you want to understand the content of this article in audiovisual form? Then take a look at our Video to acid rain!

Acid rain explained simply

Under acid rain you can imagine precipitation, the one PH value below 5.5 has. This means that the pH value of acid rain is below that of normal rain, which is 5.5 - 5.7. The pH value is a measure of whether a solution is basic or acidic. The lower the pH, the more acidic the solution.

Acid rain mainly occurs when pollutants emitted (e.g. from power plants) combine with water in the clouds. This lowers the pH of the water. The clouds can also carry this chemical compound to distant regions and release it there.

Acid rain can have negative effects on bodies of water, plants and buildings, among other things.

Acid rain refers to precipitation with a pH value below the pH value of pure rainwater. Below a pH value of 5.5 it is considered acidic. Its acidic properties can negatively affect the entire biosphere.

Acid rain formation

Basically, acid rain occurs in connection with nitrogen oxides (NOX) or sulfur oxides (SOX) like sulfur dioxide (SO2).

Acid rain causes

The biggest cause of acid rain is that Air pollution. This ensures that the composition of the air changes. However, since human activities have polluted the atmosphere in the past few decades, polluted air is the norm these days. Therefore, the “degree of air pollution” is mainly responsible for acid rain.

The causes of air pollution are varied. The following sectors are mainly responsible for this:

  • Industry (especially burning of fossil fuels such as petroleum)
  • Traffic (e.g. cars and aviation)
  • private households (e.g. heating and lighting)
  • Agriculture (e.g. pesticides)

In these sectors in particular, the pollutants are emitted in the form of solid particles, gases or aerosols.

But acid rain can also form in the vicinity of active volcanoes. A lot of gases escape here during the eruption, including sulfur dioxide in particular. This can combine with the rain.

Acid rain formula

You can also describe the formation of acid rain with a chemical reaction equation. As you already know, on the one hand, it can be connected to Sulfur oxides (SOX) like sulfur dioxide and on the other hand through the connection with Nitrogen oxides (NOX) form.

sulfurdioxide (SO2) is formed when sulfur (S) enters the atmosphere and mixes with oxygen (O2) connects:

Some molecules of sulfur dioxide can combine with oxygen again to form sulfurtrioxide (SO3):

Sulfur dioxide and sulfur trioxide dissolve in water and form sulfurous acid (H.2SO3), or sulfuric acid (H2SO4):

The higher the concentration of these acids in the cloud water, the more acidic the rain, i.e. the lower the pH value.

At the high temperatures, especially in industry, nitrogen oxides such as nitrogen dioxide (NO2) form.
To do this, the nitrogen contained in the air (N2) with oxygen first to nitric oxide (2NO):

The nitrogen monoxide combines with oxygen to form nitrogen dioxide. This is also in the gas phase as dinitrogen tetroxide (N.2O4) in front:

NO2 and N2O4 can now with water to nitrous acid (ENT2) and nitric acid (ENT3) respond:

Acid rain effects

Acid rain can have a variety of effects. In particular, bodies of water, plants and the soil as well as buildings are severely affected.

Effects on waters

When acid rain falls in a wide variety of bodies of water, it can cause their pH value to drop sharply. The pH value of natural waters can sometimes fluctuate between 6.5 and 8.5.

The acid rain can bring the pH below this level, which can damage or even kill small organisms and plants. It can also become toxic in the acidic environment Metal ions enrich better, which are also very harmful.

Overall, this low pH can for example be over a longer period of time Metabolic processes inhibit or the biodiversity reduce.

Effects on plants

Plants take up their nutrients primarily through the soil. When the soil becomes acidic, toxic metal ions are deposited again, making it difficult for the plants to absorb nutrients and grow. In addition, the plants are much more susceptible to various diseases.

Over a longer period of time, the acidified soil can even kill entire forests (= Forest dieback) to lead.

Effects on buildings

Not only nature but also some buildings can be damaged by acid rain. Sandstone, limestone, concrete or marble in particular can be attacked by the acid. Due to this acid damage, the weathering (= Rock decomposition) of the building faster and more repairs are necessary.

Many historical buildings and statues such as the Taj Mahal in India or the Acropolis in Athens, which are affected by acid rain for a long time, are significantly damaged.

Acid rain countermeasures

Because of the severe consequences of acid rain, it is important to take countermeasures early on. You can either treat the symptoms or fix the causes directly.

While treating the symptoms is relatively straightforward but short-term, treating the cause can bring relief over the long term.

Measures against symptoms

To alleviate the symptoms, it is used in many areas in Europe lime scattered by helicopter. This lime is able to raise the pH of the soil and improve the soil structure. For example, it can increase the water storage capacity of the soil and improve aeration, which facilitates root growth.

Measures against causes

The first measure against the causes of acid rain took place in Germany in the 1980s. The rule was introduced that in large fossil fuel power plants the outflowing gases desulfurized Need to become. Thus, fewer sulfur oxides (SOX) into the atmosphere and the sulfuric acids were more difficult to form. In internal combustion engines such as cars or airplanes, the sulfur is removed directly from the fuels before use.

While sulfur oxides are relatively easy to remove, nitrogen oxides are much more difficult to remove. This is mainly due to the fact that the air consists to a large extent of nitrogen (approx. 78%).


  • Acid rain is precipitation with one PH value below 5.5
  • It is created by the combination of water with pollutants such as nitrogen oxides and sulfur oxides
  • The acidic properties can have negative effects on water, plants and buildings, among other things
  • Countermeasures can be taken against the symptoms or directly against the causes

PH value

In order for you to understand what constitutes acid rain, it is important to know what the pH value is. We'll explain this to you quickly and easily in our video. Check it out right now!