How does the pH of 400mL of water change when
a. 100mL 0.0500M NaOH is added?
b. 100mL 0.0500M HCl is added?
To determine how the pH of the water changes when certain substances are added, we need to consider the nature of those substances and their effect on the water's acidity or alkalinity.
a. When 100mL of 0.0500M NaOH (sodium hydroxide) is added to the 400mL of water, it will cause the water to become more alkaline. Sodium hydroxide is a strong base that dissociates completely in water, yielding hydroxide ions (OH-) which results in an increase in the concentration of hydroxide ions. These hydroxide ions then react with the hydrogen ions (H+) present in water and reduce their concentration. As a result, the pH of the water increases, indicating a more alkaline or basic environment.
b. Conversely, when 100mL of 0.0500M HCl (hydrochloric acid) is added to the 400mL of water, it will cause the water to become more acidic. Hydrochloric acid is a strong acid that dissociates completely in water, releasing hydrogen ions (H+). These additional hydrogen ions increase the concentration of protons, which lowers the pH of the water. Thus, the pH of the water decreases, indicating a more acidic environment.
To calculate the exact change in pH, we need to know the initial pH of the water. pH is a logarithmic scale that measures the concentration of hydrogen ions in a solution. Using the initial pH value, we can apply appropriate mathematical calculations to find the final pH after the addition of the sodium hydroxide or hydrochloric acid.
Note: It's important to handle these chemicals with caution and follow proper safety protocols, as they can be hazardous.