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?

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).

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.

1 x 10-3 is bigger than 8,5 x10-3 so ph of 7 is right as it have high concetration of OH ions

No im wrong vice versa ph of 7.93 is right sorry

Wouldn’t it be 12.6 since thats the highest concentration

To determine which solution has the highest concentration of hydroxide ions, we need to consider the pH values given in the question.

The pH scale measures the concentration of hydrogen ions (H+) in a solution. It is a logarithmic scale, which means that every unit change in pH represents a tenfold difference in the concentration of hydrogen ions.

The concentration of hydroxide ions (OH-) can be calculated using the equation:

pOH = 14 - pH

where pOH is the negative logarithm of the hydroxide ion concentration. Since we are looking for the solution with the highest concentration of hydroxide ions, we need to find the solution with the lowest pOH value.

Let's calculate the pOH values for the given pH values:

a) pH = 7.93
pOH = 14 - 7.93 = 6.07

b) pH = 12.59
pOH = 14 - 12.59 = 1.41

c) pH = 7.00
pOH = 14 - 7.00 = 7.00

d) pH = 9.82
pOH = 14 - 9.82 = 4.18

e) pH = 3.21
pOH = 14 - 3.21 = 10.79

From these calculations, we can see that the solution with the lowest pOH value (highest concentration of hydroxide ions) is option c) with a pH of 7.00.

If the question asked for the solution with the highest concentration of hydronium ions, the answer would be different. Hydronium ions (H3O+) are formed when a water molecule combines with a hydrogen ion. In an aqueous solution, the concentration of hydronium ions is the same as the concentration of hydrogen ions (H+).

In that case, the answer would be the solution with the lowest pH value because a low pH indicates a high concentration of hydrogen (hydronium) ions.