Question #13933

1 Answer
Sep 29, 2015

4.0 * 10^(-5)"mM"4.0105mM

Explanation:

Extracellular fluid, or ECF, is being kept at a pH of approximately 7.47.4, which means that the concentration of hydrogen ions, "H"^(+)H+, is

["H"^(+)] = 10^(-"pH")[H+]=10pH

["H"^(+)] = 10^(-7.4) = color(green)(4.0 * 10^(-8)"M")[H+]=107.4=4.0108M

In the context of extracellular liquid, it's useful to express this value in milimoles per liter, or milimolar

4.0 * 10^(-8)color(red)(cancel(color(black)("moles")))/"L" * (10^3"mmoles")/(1color(red)(cancel(color(black)("mole")))) = 4.0 * 10^(-5)"mM"

By comparison, the concentration of sodium cations, "Na"^(+), is in the range

["Na"^(+)] = "136-145 mEq/L"

and the concentration of bicarbonate anions, "HCO"_3^(-), is in the range

["HCO"_3^(-)] = "22-28 mM"

http://anaphyteachushowtoblog.blogspot.ro/2012/01/chapter-23-urinary-system-and-body.htmlhttp://anaphyteachushowtoblog.blogspot.ro/2012/01/chapter-23-urinary-system-and-body.html

For example, the concentration of the bicarbonate anions is

(28color(red)(cancel(color(black)("mM"))))/(4.0 * 10^(-5)color(red)(cancel(color(black)("mM")))) = 7 * 10^5

higher than the concentration of hydrogen ions.

As a cool fact, concentrations of hydrogen ions that either exceed 12.0 * 10^(-5)"mM" or fall below 2.0 * 10^(-5)"mM" are not compatible with life.