# Which of the following has the greatest concentration of hydrogen ions? How is this determined?

Cola (pH 3)

#### Spiegazione:

pH is a shorthand numerical value that represents the concentration of hydrogen ions in solution.

The scale 0-14 represents the usual range of possible concentrations of protons (H^+) in an aqueous system.

Possiamo considerare H^+ to mean the same as H_3O^+ (a water molecule carries
il H^+).

"pH" is the negative log of hydrogen ion concentration, meaning that:

"pH" = -log[H_3O^+] = -log[H^+]

and therefore:

10^-"pH" = [H^+]
10^(-3) = 1.0 × 10^(-3)color(white)(l) "mol/L"

Let's simplify:

"pH"color(white)(m) [H^+] ("mol/L")
color(white)(ll)3color(white)(mml)1 × 10^(-3)
color(white)(ll)5color(white)(mml)1 × 10^(-5)
color(white)(ll)7color(white)(mml)1 × 10^(-7)
color(white)(ll)9color(white)(mml)1 × 10^(-9)
color(white)(l)11color(white)(mm)1 × 10^(-11)

This is counter-intuitive without the background information (i.e. the negative log) but, as you increase pH, you decrease the concentration of H^+.

As you decrease the pH, you increase the concentration of H^+.