Question

What is the pH of normal rainwater?

Answer 1

Hint: pH is a chemistry scale for determining the acidity or basicity of aqueous solutions. Acidic solutions (those with a greater concentration of H⁺ ions) have a lower pH than basic or alkaline solutions. The pH scale is logarithmic, indicating the concentration of hydrogen ions in a solution in reciprocal order. Since the pH formula approximates the negative of the base $10$ logarithm of the molar concentration of hydrogen ions in the solution, this is the case. pH is defined as the negative of the base $10$ logarithm of the H⁺ ion's action.

Complete step by step answer:
We must know that because of the presence of carbonic acid (${H_2}C{O_3}$), most rainwater has a pH of $5.6$ to $5.8$. The above is made up of $C{O_2}$ gas dissolved in water. The $C{O_2}$ is from the atmosphere, which has about $380$ parts per million of $C{O_2}$. Acid rain is defined as pH values of less than $5.6$, while simple rain is defined as pH values of greater than 5.6. These names are somewhat at odds with the standard pH scale, which classifies $7$ as "neutral," $7$ as "acid," and $7$ as "base." In the case of rain, excessive acidity or basicity is measured in relation to $C{O_2}$-${H_2}O$ equilibrium levels of $5.6$ to $5.8$. Rain pH will deviate from the $C{O_2}$-${H_2}O$ equilibrium due to both natural and non-natural sources of materials.
Hence the pH of normal rainwater is $5.6$ to $5.8$.

Note: It must be noted that the pH value of pure water is $7$. This attribute is neutral, meaning it is neither acidic nor basic. The pH of normal, clean rain is between $5.0$ and $5.5$, which is mildly acidic. Rain becomes even more acidic as it mixes with sulfur dioxide or nitrogen oxides, which are formed by power plants and vehicles. Acid rain usually has a pH of $4.0$. As the pH drops from $5.0$ to $4.0$, the acidity increases by a factor of ten.