ph and buffers pre-ap biology. bellwork you have a large puddle of water on the floor, explain how...
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![Page 1: PH and Buffers Pre-AP Biology. Bellwork You have a large puddle of water on the floor, explain how the sponge works to remove the water. How do you remove](https://reader036.vdocument.in/reader036/viewer/2022062621/551bd34a550346b4588b55df/html5/thumbnails/1.jpg)
pH and Buffers
Pre-AP Biology
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Bellwork
You have a large puddle of water on the floor, explain how the sponge works to remove the water. How do you remove the water collected by the sponge?
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Objectives
Define pH Explain why the pH scale is logarithmic Distinguish between acids and bases Explain how a buffer works
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Dissociation of Water Water molecules break down
• into hydrogen ions (H+) and hydroxide ions (OH-)
• H2O H+ + OH –
• [ H+][OH-] =10-14
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pH Scale pH = -log [H+] Use logarithms to make scale
more compact Called a “Log Scale”
Like Richter Scale Each pH Unit represents a power of 10
[H+]=[OH-] @pH = 7 (neutral)
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pH Scale Problem
Cola has a pH of 3 and blood plasma has a pH of 7. How much greater is the hydrogen ion concentration of cola than blood plasma?
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pH Scale Problem
Milk of magnesia has a pH of 10. Vinegar has a pH of 3. How much greater is the hydrogen ion concentration of vinegar relative to Milk of Magnesia?
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Acids Increase H+ concentration in solution H+ > OH- is an acidic solution pH < 7; [H+] > [OH-] Example: HCl
HCl H+ + Cl-
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Bases
Created in one of two waysReduce H+ concentration
Ex. NH3 + H+ NH4+
Increase OH- concentration Ex. NaOH Na+ + OH-
pH > 7; [OH-] > [H+]
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pH problems
If [OH-] is 1 x 10-11 M
a.What is the [H+] concentration?
b.What is the pH?
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Practice Problem
If the pH is 1, what is the [H+] and [OH-]?
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Biological Significance
Strong acids aid in digestion Blood = 7.4, which helps carry oxygen
throughout your body
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Role of Buffers
Chemicals that moderate pH by accepting H+ when too acidicby donating H+ when too basic
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Link to Bellwork
How is a Buffer like a sponge?
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Buffer Question
If I add an acid to water what will happen to the pH?
If I add an acid to a buffer what will happen to pH?
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17
SnapshotSnapshotWrite a
“snapshot” of today’s
learning in 25 words or less.
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