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# pH Scale

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by

## Katherine Crocker

on 4 February 2016

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#### Transcript of pH Scale

What is a “mole”?
A mole is a measurement of the amount of a chemical substance that contains as many atoms, molecules, ions, electrons, protons, etc., as there are atoms in 12 grams of pure carbon-12.
A mole is represented by the number 6.02x10^23.
What does "moles per liter” mean?
Moles per liter is the amount of moles of a substance per liter of a solution.
To calculate the pH of a solution you need to know the hydrogen ion concentration in moles per liter also know as molarity.
pH Scale Project
What does pH stand for?
Power of hydrogen
'p' stands for "Potenz", a German word, which means power
'H' is the symbol for the element "Hydrogen"
Delaney Taylor, Holly Prince, Katherine Crocker
What does “hydrogen ion concentration” mean?
The pH scale
The 3 examples from the video with work
A solution with a concentration of hydrogen ions higher than 10-7mol/L is acidic
A solution with a lower concentration is basic.
The formula is pH=-log[H+].
1-6 acid
7 neutral
8-14 alkaline
Example One
Example Two
Lemon Juice is pH 2
What is the concentration of H+ ions? Use pH formula.
ph = -log [H+]
2 = -log [H+]
divide both sides by -1
-2 = log [H+]
take the inverse log
10^-2 = 10^(log[H+])
recall 10^log(x) = x
0.01 = [H+]
[H+] = 1 x 10^-2 moles/liter
Laundry Detergent is pH 8.5.
What is the concentration of H+ ions?
Problem One
pH=-log[H+]

The H+ concentration of a solution is 0.0001 M/l, what is the pH of the solution?
-8.5=log[H+]

Example Three
Soda [H+] = 3.16 x 10^-3 moles/liter
What is the pH?
ph = -log [H+]
pH = -log (3.16 x 10^-3)
pH = 2.5 moles/liter
pH = - (-4) = 4
10^-8.5=10^(log[H+])
Use the equation pH = -log[H+]
[H+]=3.16x10^-9 moles/liter
So, the pH is 4 if the H+ concentration is 0.0001 moles/liter.
divide both sides by -1
take the inverse log
What is more dangerous, an acid or a base?
A base is more dangerous but they can both be harmful, an acid can burn through our teeth enamel but bases can burn our skin and organs.
Sources
https://spinel-science.wikispaces.com/Acids+and+Bases

http://www3.epa.gov/acidrain/education/site_students/whatcauses.html
Problem Two
Problem Three
The pH of blood is 7.35, what is the H+ concentration?
The lowest pH recorded for rain was 3.6 in the Great Smoky Mountains National Park. Determine the H+ concentration and research what causes acid rain. Cite your source.
7.35= -log[H+]
-7.35=log[H+]
10^-7.35=10^(log[H+])
0.000000045 = [H+]
H+ = 4.5*10^-8 moles/liter
pH = -log[H+]
3.6 = -log[H+]
-3.6 = log[H+]
10^-3.6 = 10^(log[H+])
0.00025 = [H+]
[H+] = 0.00025
H+ = 2.5*10^-4 moles/liter
According to EPA.gov "acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain. Sulfur dioxide and nitrogen oxides dissolve very easily in water and can be carried very far by the wind. As a result, the two compounds can travel long distances where they become part of the rain, sleet, snow, and fog that we experience on certain days."
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