What Will Happen to the pH of Water If HCI Is Added?
26 SEP 2017
The pH scale describes the acidic or basic nature of a solution. The values of pH typically range from zero, which is very acidic, to 14, which is very basic. Water has a neutral pH of seven. HCl is known as hydrochloric acid when it is in an aqueous solution. Hydrochloric acid has a pH of zero in a one molar solution. As you add HCl to water, it will lower the pH of water.
1 The Components of Water
Water's chemical formula is H2O. This means that it has two atoms of hydrogen for every one atom of oxygen. When a hydrogen ion is introduced into water, it will combine with a water molecule to form an H3O+ ion. The pH scale is based on the concentration of H3O+ ions in a solution. In water, the concentration of H3O+ is balanced by an equal concentration of OH- ions. Hence, its pH is neutral. An acidic solution has a higher concentration H3O+ ions than OH- ions. A basic solution has a higher concentration of OH- ions than H3O+ ions.
2 What Happens When HCl is Added?
When HCl is added to water, it donates an H+ ion to the water, leaving a Cl- ion in solution. This increases the H+ activity of the solution without increasing the concentration of OH- ions in the solution. Hence, the pH of water becomes more acidic; as you add an increasing amount of HCl, the pH gets lower.
3 How Do You Detect Changes in pH?
Indicators are chemicals that change color once a solution's pH changes. There are a number of different indicators, each with a specific pH range. If you are monitoring the change in pH as you add HCl to water, you should use an indicator that changes color in a pH range below seven. Thymol blue, methyl orange and methyl red all change color in a pH range below seven.
4 How is pH Calculated?
Because the concentration of H3O+ ions can change drastically with small additions to a solution, this is not a straightforward way of communicating pH. Instead, we look at the exponential nature of that concentration using the logarithmic function. The pH of a solution is defined as the negative base ten logarithm of the H3O+ concentration of a solution. This separates values on the pH scale by powers of ten.