## M

ductivity measurements of pure water, is 1.8 X 10 at 25 °C. Substituting this value for Keq in Equation 2-4 gives the value of the ion product of water:

Kw = [H+][OH-] = (55.5 m)(1.8 X 10-16 m) = 1.0 X 10-14 m2

Thus the product [H+][OH-] in aqueous solutions at 25 °C always equals 1 X 10-14 m2. When there are exactly equal concentrations of H+ and OH-, as in pure water, the solution is said to be at neutral pH. At this pH, the concentration of H+ and OH- can be calculated from the ion product of water as follows:

As the ion product of water is constant, whenever [H+] is greater than 1 X 10-7 m, [OH-] must become less than 1 X 10-7 m, and vice versa. When [H+] is very high, as in a solution of hydrochloric acid, [OH-] must be very low. From the ion product of water we can calculate [H+] if we know [OH-], and vice versa (Box 2-2).

## Lose 10 Pounds Naturally

Studies show obesity may soon overtake tobacco as the leading cause of death in America. Are you ready to drop those extra pounds you've been carrying around? Awesome. Let's start off with a couple positive don't. You don't need to jump on a diet craze and you don't need to start exercising for hours each day.

## Post a comment