The hydroxide ion concentration in pure water at 25ºc is not equal to
a. the hydronium ion concentration.
b.1 x 10^-7 m.
c. the hydroxide concentration in a solution with a ph of 7.
d.1 x 10^7 m.

The hydroxide ion concentration in pure water at 25ºC is NOT equal to 1×10⁷ M

Option D. 1×10⁷ M gives the correct answer to the question.

Water has the following ions

1. Hydrogen ion (H⁺)

2. Hydroxide ion (OH¯)

H₂O <=> H⁺ + OH¯

From the above equation, we can see that water contains equal amount of Hydrogen ion, H⁺ and hydroxide ion, OH¯.

Pure water has a pH of 7 and a pOH of 7.

Thus, the concentration of Hydroxide ion, OH¯ can be obtained as follow:

pOH = 7

pOH = –Log [OH¯]

7 = –Log [OH¯]

Multiply through by –1

–7 = Log [OH¯]

Take the antilog –7

[OH¯] = antilog (–7)

From the above illustration, we can conclude that the hydroxide ion concentration in pure water at 25ºC is NOT equal to 1×10⁷ M

Option D. 1×10⁷ M gives the correct answer to the question.

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