Question

*****CHEMISTRY HELP IN EXCHANGE FOR MEDAL *****

What would the pH of a solution that had a hydroxide ion concentration of 1 x 10-9 M be?

I want to know how to do the math, and would appreciate a step by step explanation with numbers.

Answer 1

Ok since we have the hydroxide ion concentration we are going to need to get the pOH then solve for the pH using that.

Answer 2

pOH = -log [OH^-] is the equation we are going to use to get the pOH.
Using what you gave 1 * 10^9 M we are going to plug this in as
pOH = -log [OH^-]
pOH = -log [1x10^9]

Answer 3

Thank you @DKace! You're amazing. (-^J^-)

Answer 4

There are 2 methods to solve this problem. The first method is to calculate from [OH] the pOH and from the pOH determine the pH.

Step 1: To calculate the pOH take the -log of [OH] which is: \[-log[1\times 10 ^{-9}] = 9 \]
Step 2: pH + pOH = 14
To solve for pH write the following equation pH + 9 = 14. Subtract 9 from both sides pH = 5.

The second method is to calculate the [H3O] and from [H3O] calculate the pH.
\[[H_{3}
O][OH] = 10^{-14}\]
Step 1: Write out the following equation [H3O][1x10^-9] = 10^-14. Divide both sides by 1x10^-9. [H3O] = 1x10^-5M.

Step 2: Calculate pH directly from [H3O]. -log[1x10^-5] = 5