Question

A student measures the pH of a solution to be 6.8. Which should the student add if she wants to decrease the pH of the solution?

Answer 1

To decrease the pH of a solution measured at 6.8, a student should add an acid like hydrochloric acid (HCl) dropwise to increase the hydronium ion concentration and lower the pH value.

Step-by-step explanation:

If a student measures the pH of a solution to be 6.8 and wants to decrease the pH of the solution, they should add an acid, because acids increase the hydronium ion concentration ([H3O+]) which lowers the pH. A common acid used in laboratories for this purpose is hydrochloric acid (HCl). The student can add 0.5 M HCl dropwise to the solution to carefully lower the pH to the desired level. It's important to add the acid slowly and measure the pH after each addition to avoid overshooting the target pH.

As the acidity of the solution increases, the pH value decreases. This is because the pH is defined as the negative logarithm of the hydronium ion concentration, and when that concentration increases, the logarithm becomes more negative, hence a lower pH.

Answer 2

The answer would be to add an acid. This would decrease its pH. Hope I helped!