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### Calculating pH or pOH with Molarity

Posted: Sat Dec 08, 2018 8:27 pm
Are there questions where you have to find the molarity or will that always be a given?

### Re: Calculating pH or pOH with Molarity

Posted: Sat Dec 08, 2018 8:33 pm
Dr. Lavelle might give us a multistep question to involves both fundamentals as well as acids and bases. So he might first ask for us to calculate the molarity of a solution by only giving us the amount of substance and the total volume of the solution, and then ask us to find the pH of the solution.

### Re: Calculating pH or pOH with Molarity

Posted: Sat Dec 08, 2018 8:39 pm
In order to calculate the pH of an aqueous solution you will need to know the concentration of the hydronium ion in Molarity. pH=-log[H30+]. For example if given the problem pH of a 0.0025 M HCl. pH= -log(0.0025) = 2.60. Similar process with pOH, but you must know the concentration of the hydroxide in Molarity.

### Re: Calculating pH or pOH with Molarity

Posted: Sat Dec 08, 2018 8:48 pm
Even when the molarity of a substance is given, sometimes the molarity used to calculate pH will be different because it is based on molarity of H3O+ and not the given molarity.