You need to calculate the extent of dissociation of acid for calculating the pH. It will be closer to 7 but will never equal to 7 as its an acid.
can u explain me..pls..how to calculate the extent of dissociation..?
Degree of dissociation i not required for the strong acids like HCl etc that dissociates completely but for the organic acids like acetic acid that dissociae partially leaving the proton conc. lower than expected.
Consider an example for calculating pH of 6X10^-9
You still CAN use the equation pH = -log [H+]
Just be careful when finding the value of [H+]
If there is no dissolved HCl ; pH of water is 7
which means that [H+] = 10^-7
with 6 x 10^-9 M HCl
= ( 1 x 10^-7 ) + ( 6 x 10^-9 )
= ( 1.06 x 10^-7 )
pH = - log ( 1.06 x 10^-7 )
= - ( -7 + 0.0253 )
= 7 - 0.0253
= 6.9747 ____ ( round up to 6.97 )
Hope that helps you understand a bit better
ya..thank u very much..