A solution of ammonia has a pH of 11.8. What is the concentration of OH - ions in the solution? Useful formulas ...

They are asking you for OH - ions concentration, which is why you have to find the pOH of the solution. You can easily do this with this formula:

pH + pOH = 14

Solve for pOH and you get:

pOH = 14 - pH

Replace the pH with it's value:

pOH = 14 - 11.8

pOH = 2.2

Now that you have the pOH you can find the concentration of OH - ions with this formula:

pOH = - log[OH-]

Solve the formula for [OH-] and you get:

[OH-] = 10^ (-pOH)

Now replace pOH with it's value:

[OH-] = 10^ (-2.2)

[OH-] = 0.006309 M

The concentration of OH - atoms is 0.006309M or in the scientific notation 6.309*10^ (-3) M

Its B

Explanation:

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