Now , I know that most of you are going to say that nicotinic acid is a strong acid, but our professor wants us to use the formula for weak acids instead, who knows why
Can somebody check if they get the same answers as I do?
300 g of nicotinic acid (molar mass: 123 g / mol, pKa value: 2.03) are dissolved in 250 ml of water.
A) What is the pH value of the solution?
B) What is the pH value of the solution after six-fold dilution?
I first calculated the amount of substance, I got 2,4 moles.
Then I calculated the concentration.
I got about 9.6 mol /l. And with the pH-value formula for weak acids (pKs-value is small, but according to our professor we should see this as a weak acid!) I got a pH value of 0.52.
For B) I used: c1 * V1 = c2 * V2 considering that V2 = V1 * 6
The concentration for the new solution would thus be 1.6 mol / l. My pH value after my six-fold solution would therefore be 0,91.
Thank you very much guys for helping me!