pH of ions

[Shreya Thyagarajan Dis1A]

Hi, I’m still a little bit confused on how to determine which ions will affect pH and which ones won’t?

[Arjan G 2H]

Hi! An easy way to see if an ion will affect pH is to remember what type of acid or base the conjugate molecule comes from. Typically, a strong base has a weak conjugate acid and a strong acid has a weak conjugate base. But, a weak acid has a strong conjugate base and a weak base has a strong conjugate acid. So, the conjugate acids and bases that derive from weak acids and bases are the ones that will have an effect on the pH. If the conjugates are a weak acid and a strong base, then the pH will increase and if the conjugates are a strong acid and weak base, then the pH will decrease. I hope this helps!

[Mari Masunaga 1G]

Hi. I think it helps to think about the salts conjugate acids and bases. For example, when NaF is dissolved in water it will form NaOH and HF. NaOH is a strong base however HF is a weak acid, therefore the pH of the solution is affected more by the NaOH and it will be more basic. If NaCl were to be dissolved in water however the pH would be unaffected because both NaOH is a strong base HCl is a strong acid. I like to think they kind of "cancel" each other out. hope this helps

[Ethan Mai 1D]

One way to determine whether ions will make a solution more basic or acidic is to determine the conjugate base or acid for each ion. If the conjugate base/acid of the ion is strong, then the ion itself is weak and has little effect on the pH. If the conjugate base/acid of the ion is weak, then the ion is stronger than its conjugate counterpart and will accordingly affect the pH of the solution in that manner.