What is the concentration of hydroxide ions in a solution with a pH of 9.00?
pH = 9
pOH = 14-9
pOH = -log(OH^-)
To find the concentration of hydroxide ions ([OH-]) in a solution with a given pH, we can use the pH scale and the relationship between [H+] (concentration of hydrogen ions) and [OH-] in water.
The pH scale measures the acidity or alkalinity of a solution. On the pH scale, a solution with a pH of 7 is considered neutral, while solutions with pH values less than 7 are acidic, and values greater than 7 are alkaline or basic.
The pH scale is defined as:
pH = -log[H+]
where [H+] represents the concentration of hydrogen ions in mol/L.
In pure water, [H+] and [OH-] are equal since water molecules dissociate into equal amounts of hydroxide and hydrogen ions. So, the product of [H+] and [OH-] in water remains constant:
[H+][OH-] = 1 x 10^(-14) (at 25°C)
By rearranging this equation, we can express [OH-] in terms of [H+] as:
[OH-] = 1 x 10^(-14) / [H+]
Since the given pH of the solution is pH 9.00, we can calculate [H+] using the definition of pH and the reverse of the logarithmic equation:
pH = -log[H+]
Rearranging for [H+], we get:
[H+] = 10^(-pH)
Thus, [H+] = 10^(-9.00).
Now, substituting this value into the equation for [OH-]:
[OH-] = 1 x 10^(-14) / [H+]
[OH-] = 1 x 10^(-14) / 10^(-9.00)
Simplifying this equation by using the rule of exponents (subtracting exponents when dividing):
[OH-] = 1 x 10^(-14 + 9.00)
[OH-] = 1 x 10^(-5.00)
Therefore, the concentration of hydroxide ions ([OH-]) in the solution with a pH of 9.00 is 1 x 10^(-5.00) M.