*Warm Up

*Name the following acids:

*HI

*HNO3

*HCl

*Write the formula for the following acids:

*Hydrofluoric Acid

*Nitrous Acid

*Hydrobromic acid

Unit 10, Day 2

Kimrey

17 May 2013

*pH Calculations

*Objectives

*Identify strong and weak acids

*Calculate the pH and pOH of an acid given a concentration.

*Determine the concentration of an acid given a pH or pOH.

*Strong Acids and Weak Acids

*There are two strengths of acids: strong and weak.

*Strong acids completely dissociate (break up) in water.

*Weak acids do not completely dissociate.

*There are 6 strong acids.

*HCl

*HBr

*HI

*H2SO4

*HNO3

*HClO4

*pH

*pH is a logarithmic scale that measures the concentration of the [H+] ion in solution.

*Goes from 0 -14

* 0 - 6.99 is acidic

*14 – 7.01 is basic

*pH = -log[H+]

*[H+]=10-pH

*Logs and anti logs…oh my!

*Don’t freak over logs and anti-logs, your calculator does them for you!

*Ex. Find the pH of a HCl solution with a H+ concentration of 1 x 10-6.

*pH = -log[H+]

*pH = 6

*Hydronium

*When acids break up, the concentration of hydrogen is sometimes explained by using hydronium

*Hydronium is H3O

*Water + Hydrogen

*Just do math the same way!

*Example

*Find the pH of a 0.03 M solution of HBr.

*pH = -log[H+]

*pH = 1.5

*Example

*What is the concentration of a HCl solution that has a pH of 3?

*[H+]=10-pH

*[H+] = .001M

*pOH

*Same as pH, but opposite.

*Goes from 0 -14

* 0 - 6.99 is basic

*14 – 7.01 is acidic

*pOH = -log[OH-]

*[OH-]=10-pOH

*Example

*Calculate the pOH for a solution of NaOH with a concentration of 1 x 10-4 M.

*pOH = -log[OH-]

*pOH = 4

*Example

*Calculate the pOH for a solution of KOH with a concentration of 0.45 M.

*pOH = -log[OH-]

*pOH = .35

*Example

*What is the concentration of a solution the has a pOH of 13.5?

*[OH-] = 10-pOH

*[OH-] = 3.16 x 10 -14 M

*pH and pOH

*Remember that both the pH and pOH scale go from 0-14.

*As the concentration of [H+] or [OH-] goes up the other must go down.

*These two relationships allows us to assume that:

*pH + pOH = 14

*Example

*What is the pH of a solution that is found to have a pOH of 10?

*pH = 4

*Example

*What is the pH of a .067 M solution of LiOH?

*pOH = 1.17

*pH = 12.8

*Example

*What is the pOH of a 0.0056 M solution of HCl?

*pH = 2.25

*pOH = 11.75

*Exit Card

*What is the pH of a solution HI with a concentration of .0089 M?

*What is the concentration of a strong acid with a pH of 3.45?

*What is the pH of a solution of a NaOH with a concentration of 5.67 x 10-4 M?