will the pH of 1M nitric acid and 1M formic acid be the same?

Question

why?

why?
do molarity give effect on pH??

Answer 1

No because HNO3 is a strong acid and formic acid is a weak acid. " Weak " means that only a small fraction of the molecules are dissociated into H+ and another fragment ( such as HCOO-)
To explain this we can consider a solution of 1 M of nitic acid
HNO3 >> H+ + NO3-
[H+] = 1 M
pH = - log 1 =0
Let us consider a solution of 1 M HCOOH ( Ka = 1.8 x 10^-4)
The equilibrium is :
HCOOH <----> H+ + HCOO-
initial concentration
1 M . .. . . .. . . . 0. . . .. 0
at equilibrium
1 - x .. . . . . . . . . x. . . . . x
Ka = x^2 / 1 - x
x = [H+] = 0.0134 M
pH = - log 0.0134 = 1.87

Molarity gives effect on pH because pH = - log [H+]
[H+] is the molar concentration of H+
Example :
we have a solution which is 0.1 M HCl ( strong acid ) and anothe solution which is 0.01 M in HCl.
In the first case pH = - log 0.1 = 1.
In the second case pH = - log 0.01 = 2

Answer 2

No, they will not be the same pH. Each acid breaks up into ions in solution with water, however some acids break up more completely, they are strong acids. The molarity of the acid used does affect the pH but you need to know which acid it is to calculate the pH. 1 M of nitric acid does not produce the same number of "acid ions" as 1M of formic acid.

Answer 3

No.

Nitric acid completely disassociates into nitrate ions and hydrogen ions. Therefore, the pH is directly porportional to the molarity. Nitric acid is a "strong" mineral acid.

Formic acid only partially dissassociates. Besides formate and hydrogen ions, there is still formic acid molecules.The pH is dependant on the dissassociation constant under these circumstances. Formic acid is a "weak" organic acid.

Answer 4

Molarity is not the only factor altering pH - the strength of the acid is also important. Nitric acid is a strong acid, and thusly dissociates completely:

HNO3 (aq) ---> H+ (aq) + NO3- (aq)

1 mol of nitric acid produces 1 mol of hydrogen. Taking the
-log of that gives your pH: 0.

Formic acid, on the other hand is a weak acid. It does not dissociate completely:

HCOOH <==> H+ + HCOO-

To find out how to calculate pH of a weak acid, go to http://www.science.uwaterloo.ca/~cchieh/cact/c123/wkacids.html. You will find that the pH is a lot higher than that of nitric acid. Good Luck

Answer 5

No, The dissociation constant for formic acid will be much less than for nitric acid, because as cappucino noted, formic acid id a weak acid (ie, it does not dissociate completely). If you know the dissociation constant; you can work out the pH.

Answer 6

No, because the dissociation constant, Ka, is much higher for nitric acid than it is for formic acid. That dissociaton constant is what makes an acid strong or weak.