Calculating pH

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Miriam Sheetz 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:25 am

Calculating pH

Postby Miriam Sheetz 2B » Thu Dec 06, 2018 1:14 pm

How do you calculate the pH of an NaOH solution when given the molarity of the NaOH?

905109118
Posts: 34
Joined: Mon Oct 01, 2018 12:16 am

Re: Calculating pH

Postby 905109118 » Thu Dec 06, 2018 1:43 pm

You will need to know the molarity of the NaOH. Let's assume the solution is 0.1M. NaOH is a strong base, so this will produce 0.1mol/L of OH ions in solution. This will produce a pH of 13.
You will need to take the negative log of 0.1 to find the pOH. This will work out to be 1.
Since pH + pOH = 14
We can calculate the pH to be 13.
This assumption can only be used for strong bases which dissociate completely in water.

Catly Do 2E
Posts: 64
Joined: Fri Sep 28, 2018 12:24 am

Re: Calculating pH

Postby Catly Do 2E » Thu Dec 06, 2018 1:50 pm

For example, we are given that the molarity of a solution is 0.1M NaOH. Since we know that NaOH is a strong base, we know that it will fully dissociate. Therefore,
0.1 M NaOH --> 0.1 M OH-
pH = 14 - pOH = 14 - (-log([OH-])) = 14 - (-log([0.1M)) = 14 - 1 = 13

So, the final answer is pH = 13.


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