pH

How do acids and bases work? In solution, acids RELEASE hydrogen ions

In solution, bases RECEIVE hydrogen ions

Acids… H+

React with metals

Watery

They burn!!!

HCl, H2NO3, H2SO4, HNO3

Bases… OH-

Does not react with metals

Slimy

Burn!!!

NaOH

KOH

What happens if I mix a strong acid with a strong base?

Let’s mix HCl with NaOH….

What is pH? What does that mean?

0-14 scale used to specify acidity or alkalinity of an aqueous solution

Measure of the STRENGTH of the acid or base character of a substance

Mathematical definition? pH = -log[H+] Sometimes written as

pH= log [H3O+]

pH Calculation Concentrations are small numbers! It’s only a measure of the concentration of hydrogen ions, and those are small

Ex: Let’s figure out the pH of a solution with the H+ concentration 1x10-3◦ What is that in standard form? 0.001◦ All you do is take the negative log of that number… -log(1x10-3) and you get a pH of 3!

Types of Acids and Bases Strong Acids (about 0-2) battery acid, stomach acid, vinegar

Weak Acids (about 4-6) tea, coffee, sweat

Neutral Stuff (around 6-8) pure water, urine, saliva, blood, milk, tears

Weak Bases (about 8-10) sea water, baking soda, eggs, deodorant

Strong Bases (about 12-14) bleach, detergents, drain cleaner

Strong Acids vs Weak Acids Strong acids ionize strongly and completely and release a lot of protons!

Weak acids disassociate incompletely and release a smaller amount of hydrogen ions

Strong Bases vs Weak Bases Strong bases consume large amount of hydrogen ions, leaving the concentration low. Large pHs!

Weak bases do not consume as much hydrogen ions like their strong counterparts, so there will be more hydrogen ions left. Not as large pHs!

Flip Side! Yes, there’s a pOH –log[OH-]

How do you get it? Subtract the pH from 14!

pH + pOH = 14 ALWAYS, or 1.0x10-14 mol/L = [H+][OH-]

So, if the pH is 3.5, what’s the pOH?

YouTube Overview https://www.youtube.com/watch?v=LS67vS10O5Y