Question

Calculate the pH of a 0.01M of HCl solution.

Answer 1

Hint: To answer this question, we must know that pH stands for power of hydrogen. It is actually based on the concentration of hydrogen ions in an aqueous solution.

Complete step by step answer:
We know that pH is a measure of how acidic or basic a substance is. The scale ranges from 0 to 14, with 7 being the neutral mark. A pH of less than 7 indicates the solution is acidic while a value more than 7 indicates it is a base.
pH paper made of universal paper is a visual indicator. Different colors are associated with each pH. Strong acids and bases are compounds that are completely dissociated in water. Under normal circumstances this means that the concentration of hydrogen ions in acidic solution can be taken to be equal to the concentration of the acid. The pH is then equal to minus the logarithm of the concentration value. Hydrochloric acid is a strong acid which makes our calculation easier.

As the concentration of hydrogen ions is the same as concentration of acid in case of HCl. We can write:
\[\left[ {{H^ + }} \right] = 0.01M\]
We know, \[pH = - \log \left[ {{H^ + }} \right]\]
Therefore, substituting the concentration in the formula we get,
\[pH = - \log \left[ {0.01M} \right]\]
\[pH = - ( - 2)\]
\[pH = 2\]
Hence, the correct answer is 2.

Additional information:
pH is essential to determine the quality of water. It also indicates its solubility, biological availability of chemical constituents and heavy metals which may render it undrinkable.

Note: We must always remember that as concentration changes with temperature, the pH scale also shifts. With increase in temperature the pH decreases. This however does not mean that water becomes acidic at higher temperature. It simply means that the scale shifts and 7 is the neutral point only at normal temperature.