chemistry

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which solution has the highest concentration of hydroxide ions?

a ph=7.93
b ph=12.59
c ph=7.00
d ph=9.82
e ph=3.21

i know the answer is 7 but why is it seven? would it be different if it said hydronium ions?

• chemistry - ,

Who told you the correct answer is 7.00? That isn't right.
Reason through it.
Low pH means high pOH (since pH + pOH = 14) and that means high H^+. So for high OH^- we want a high pH which means a low pOH and that is a high OH^-. If you don't like that method, go through and calculate the concn of OH^- for each.
For example,
pH = 7.93. pOH = 6.07. OH^- = 8.5E-7
Another.
pH = 7.00. pOH = 7.00. OH^- = 1.00E-7
Another.
pH = 3.21. pOH = 10.79. OH^- = 1.62E-11
Note that for these three examples I've done, pH 7.93 has a higher OH than the other two, (including pH = 7.00).

• chemistry - ,

oh, i see, it was a question on my chem test that i got wrong, the answer sheet said 7. this teacher is always giving questions with wrong answers, its very frustrating.