129. Choose the wrong statement :-
(1) For a neutral solution : [H+] = [OH-] = √Kw
(2) For an acidic solution : [H+] >√ Kw. and
[OH-] < √Kw
(3) For a basic solution : [H+) < √Kw and
[OH-] > √Kw
(4) For a neutral solution at all temperatures
[H+] = [OH-] = 10-7 M
Answers
Explanation:
If the temperature does not vary, the following relationship between the densities of hydrogen ions (H+) and hydroxide ions (OH-) is found with any solution:
[H+][OH-]=Kw=10-14(=fixed) at 25℃
(Kw is called the ion product of water or dissociation constant of water.)
In pure water or neutral solution, the following formula holds true, because
[H+]=[OH-] ,
[H+]=[OH-]=√(Kw)=√10-14=10-7
If you know the value of either [H+] or [OH-], you can find the value of the other.
So, pH is defined by the following formula:
pH=-log10[H+]
The concentration of hydrogen ions in any solution we are likely to encounter will range from 1 mol to 0.000001 mol per liter of solution. However, solutions with extremely low hydrogen-ion concentration could conceivably rack up a pretty long parade of zeros after the decimal point. Danish biochemist S.P.L. Sorensen was the first to use the pH system we know today, which defines inverse numbers of hydrogen-ion concentration shown in common logarithm as pH. That is to say,
pH=-log10[H+]
In the case of a neutral solution,
[H+]=10-7 , which we call a pH of 7.