Which of the following solutions will show the largest pH change when 10 mL of 1 M NaOH is added to it?
(a) 10 mL of 1 M NaOH
(b) 100 mL of water
(c) 10 mL of 1 M NaNO3
(d) 10 mL of 0.01 M HOAc
(e) 100 mL of 0.1 M HOAc and 0.1 M NaOAc
Chemistry · Sun Jul 10 2022
Answered on
The solution that will show the largest pH change when 10 mL of 1 M NaOH is added to it is option (e) 100 mL of 0.1 M HOAc and 0.1 M NaOAc.
To understand why option (e) will show the largest pH change, we need to look at the properties of the different solutions. NaOH is a strong base, meaning it completely dissociates in water to produce hydroxide ions (OH-). When NaOH is added to option (a) 10 mL of 1 M NaOH, there is no change in concentration and therefore no significant pH change.
Option (b) 100 mL of water does not contain any significant amount of acid or base, so adding NaOH to it will not cause a large pH change.
Option (c) 10 mL of 1 M NaNO3 is a salt solution, which will not significantly affect the pH when NaOH is added.
Option (d) 10 mL of 0.01 M HOAc is a weak acid solution. Adding NaOH to it will cause neutralization, but the change in pH will not be as large as in option (e).
Option (e) 100 mL of 0.1 M HOAc and 0.1 M NaOAc is a buffer solution. A buffer solution is a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists changes in pH when small amounts of acid or base are added. Adding NaOH to this buffer solution will cause the acid (HOAc) to react with the base (NaOH) to form water and the conjugate base (OAc-), resulting in a significant pH change.