Calculating pH

[Pranav-Arora]

1. The problem statement, all variables and given/known data
x mole of a strong monoacidic base is dissolved in one litre of water. The pH of the solution will be
(a)-log x
(b)14-log x
(c)14+log x
(d)-log (14-x)


2. Relevant equations



3. The attempt at a solution

For instance i assumed that the base is NaOH but it does not react with water to form any compound. So i am confused how should i start?

Thanks! :smile:

[chemisttree]

I'm still working on "monoacidic base"...
What's that?

OK. I just Googled it. So you have a base that generates 1 mole of OH- per mole of base in water. You also know the following:
1) pH = -log[H+]
2) [H+][OH-] = 1.01 X 10-14

Can you get it from there?

[agent99]

First calculate the pOH, which equals to -log[OH-].
Then, pH=14-pOH. That's it.

[Pranav-Arora]

I'm still working on "monoacidic base"...
What's that?

OK. I just Googled it. So you have a base that generates 1 mole of OH- per mole of base in water. You also know the following:
1) pH = -log[H+]
2) [H+][OH-] = 1.01 X 10-14

Can you get it from there?

I think it isn't stated that it generates one mole of OH-. :smile:

[sankalpmittal]

I think it isn't stated that it generates one mole of OH-. :smile:

Monoacidic base is written in the form of MOH where M is any univalent metal.

Hints :
1 mole of MOH in water furnishes one OH- ion.
Then x moles of MOH will furnish.... ?

Write an ionic equation in terms of "x" and think about Mole Concept once again. You can then use the formulas given by chemisttree.

[Borek]

think about Gay Lussac's law and Avogadro's law.

Huh? What do the laws concerning gases have to do with the pH of the solution?

[Pranav-Arora]

This isn't a hard question as i thought of and thanks to chemistree for the idea of pOH.

I found out the pOH which is -log x. Then calculated pH, which is completely easy pH=14-pH.

@sankalp:- I think i am not that bad at chemistry that you need to remind me of Mole concept.

I just forgot to reply in this thread after solving the problem. :P

[Borek]

For a future reference: water ion product, pH and pOH (http://www.chembuddy.com/?left=pH-calculation&right=water-ion-product).