What is the pH of a 1.00 x 10–9 molar solution of HCl?

Question

What is the pH of a 1.00 x 10–9 molar solution of HCl?

Answer 1

The first two answerers are simply blindly shoving numbers into an equation without thinking. What, adding acid to water will make the solution become basic?? The fact is pure water has a pH of 7 meaning it already has proton concentration of 10^-7, 100x more than 10^-9 HCl. The amount of HCl here is minuscule. This is a trick question; the answer is the pH will be 7.00 (sig figs!).

Answer 2

No! In Q1, the pH of HCl can't in any respect be more beneficial than 7.0. you should operate a million x 10^7M (from the water) to a million x 10^-9M (from the HCl), and then take the unfavourable logarithm. In Q2 the pH is two.0.

Answer 3

You can't get alkaline pH for acids !!!

It is so dilut that you need to take into account the self dissociation of water. The later is an equilibrium so you ought to treat as such and see how it will occur in the presence of the H+ from the acid (some would simply add 10^-7 from water to that of the acid but that is wrong).

.. .. .. .. .. H2O <=> H+ +OH-
Initial .. .. .. .. .. .. .10^-9
Dissoc... ..x
Produce .. .. .. .. .. .. x .. .. .x
At Equil .. .. .. . . x+10^-9.. x

Kw=[H+][OH-] =(x+10^-9)x=10^-14 =>
x^2+10^-9x-10^-14=0
x= 9.95*10^-8

so pH= -log((9.95*10^-8)+10^-9) = 6.998
It is so dilute that the water is buffering the effect of HCl.

Answer 4

Normally, in an aqueous solution of HCl, the major species are H+, Cl-, and water. However, in this case, the amount of HCl in solution is so small that it has no effect; the only major species is water. Therefore, the pH will be that of pure water or pH = 7.00.

Answer 5

pH= -log[H+]
therefore the concentration of H+ in HCl is the same as given=1*10^-9

therefore pH=-log[ 1*10^-9]
=9

the more we increase the concentration of the acid, the more H+ are there and the lower the pH(the more acidic the solution becomes)
thus for concentation of 1*10^-5
we get:

pH=-log[ 1*10^-5]
=5

hope you are helped