pH AND CALCULATIONS Flashcards
WHAT IS pH?
negative logarithm of activity (or concentration) of hydroxonium cations H3O+ in a solution; pH scale is a logarithmic scale for expressing the acidity or alkalinity of a solution
pH = - log c(H3O+) = - log c(H+)
HOW DO YOU CALCULATE A WEAK ACID?
pH = ½ pKa - ½ log ca
HOW DO YOU CALCULATE A STRONG ACID?
pH = - log ca
WHAT DEFINES A WEAK ACID?
pKa > 2 or K ˂ 10-2
HOW DO YOU CALCULATE A WEAK BASE?
pOH = ½ pKb - ½ log cb
pH = 14 - pOH
HOW DO YOU CALCULATE A STRONG BASE?
pOH = - log cb
WHAT DEFINES A WEAK BASE?
weak base: pKb > 2 or Kb ˂ 10-2
WHAT DOES K EQUAL TO?
10^(-pK)
WHAT DOES Pk EQUAL TO?
-log (K)
WHAT DOES AMPHOTERIC MEAN?
It can act as both an acid and a base (NH3 and H2O)
WHAT IS THE DISSOCATION CONSTANT FOR WATER - Kw?
Kw = [H+] [OH-] = 1.0 x 10-14 (at 25°C)
WHAT DO YOU DO WHEN YOURE ASKED TO FIND THE pH OF A SOLUTION HAVING A CONCENTRATION OF 1.0 x 10^(-z)?
pH = “z”
1 x 10-9 M H+ ➞ pH = 9.00
CALCULATE THE pH AND THE pOH OF A 2.6 x 10-12 M OH- solution
pOH = -log (2.6 x 10-12) = 11.58
pOH + pH = 14
pH = 14 - 11.58 = 2.42
HOW DO YOU FIND THE CONCENTRATION OF [H+]?
pH = -log(H+)
-pH = log(H+)
10^-pH = 10^log(H+)
10^-pH = (H+) (10 to the log of something = that something)
HOW DO YOU FIND THE CONCENTRATION OF [OH-]?
pOH = -log(OH-)
-pOH = log(OH-)
10^-pOH = 10^log(OH-)
10^-pOH = (OH-)
CALCULATE THE CONCENTRATION OF H30+ IN A SOLUTION WITH A pH OF 5
pH = -log(H+) = -log(H30+)
[H30+] = 10^-pH
if pH = 5 solution is an acid
concentration of [OH-] = 10^-9 and [H+] = 10^-5
CALCULATE THE pH OF A 0.005M SOLUTION OF Ba(OH)2
pOH = 10^-(0.005) (2) = 1.96
pOH = 14-2
pOH = 12
CALCULATING PH
