acid/base chemistry
DESCRIPTION
Acid/Base Chemistry. The pH scale and what does it mean?. pH. What is it? What does it mean? How do you measure it? Can you determine other things from pH?. pH an Overview. pH is the measure of the concentration of hydrogen ions is a solution. pH is measured on a log scale. - PowerPoint PPT PresentationTRANSCRIPT
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Acid/Base Chemistry
The pH scale and what does it mean?
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pH
• What is it? • What does it mean? • How do you measure it?• Can you determine other things
from pH?
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pH an Overview
pH is the measure of the concentration of hydrogen ions is a solution. pH is measured on a log scale.
pH = - log[H+] pH is used to indicate the degree of acidity or
alkalinity (basic) of a solution. A solution is of a water solvent (polar)
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When there is a high [H+], the solution is acidic. On the other hand when the [H+] concentration is
low, the solution is basic.
So if there is a high [H+], there must be a low [OH-] If there is a low [H+], there must be a high [OH-]
So what does H+ and OH- create?
H2O
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Water
Pure water should have a neutral pH, due to have equal amounts of [H+] & [OH-].
Acid and bases are created by adding polar molecules to water to increase [H+], or increase [OH-]
The pH scale is used to measure the acidity or alkalinity of a solution.
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pH ScaleThe pH scale ranges from 0 to 14. 0 being the most acidic and 14 being the most basic.
So what does the pH tell us about [H+] of a solution?
If something has a pH of:pH 1 = [H+] = 0.1 MpH 2 = [H+] = 0.01 MpH 3 = [H+] = 0.001MpH 4 = [H+] = 0.0001MpH 5 = [H+] = 0.00001MpH 6 = [H+] = 1X 10-6MpH 7 = [H+] = 1X 10-7MpH 8 = [H+] = 1X 10-8MpH 9 = [H+] = 1X 10-9MpH 10=[H+] = 1X 10-10MpH 11=[H+] = 1X 10-11MpH 12=[H+] = 1X 10-12MpH 13=[H+] = 1X 10-13MpH 14=[H+] = 1X 10-14M
Representative pH Values
Substance pH
battery acid 0.5
gastric acid 1.5-2.0
lemon juice 2.4
cola 2.5
vinegar 2.9
orange juice 3.5
acid rain 4.5-5.0
tea 5.5
milk 6.5
pure water 7.0
saliva 7.0-7.4
blood 7.3-7.5
sea water 8.0
soap 9.0-10.0
ammonia 11.5
household bleach 12.5
lye (sodium hydroxide) 13.5
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How to Figure it out?
If you were given HCl with a concentration of 0.003M, what would be the pH?
pH = -log [H+]pH = -log[0.003M]
pH = 2.52
pH will not have a unit!!!
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How does pH and pOH relate?
pH and pOH relate in the following way pH + pOH = 14
pOH is the measure of the [OH-], in a solution.
What would be the pOH of an solution with a pH of 5.75?
pOH = 14 - 5.75pOH = 8.25
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If given pH
To determine the concentration from pH, one must do the following:
[H+] = 10 (-pH)
So what is the [H+] of a solution with a pH of 12.05?[H+] = 10 (-12.05)
[H+] = 8.91 X 10 -13 M
antilog
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Sample Problem 1
What is the pH and pOH of an solution with [H+] of 3.33 X 10-9 M?
1st solve for pH pH = -log [H+]pH = - log[3.33 X 10-9 M]pH = 8.48
2nd solve for pOH pOH = 14 – pHpOH = 14 - 8.48pOH = 5.52 (acidic)
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Sample Problem 2
What is the [H+] of a solution with a pOH of 4.14?1st determine pH pH = 14 – pOH
pH = 14 – 4.14pH = 9.86 (basic)
2nd determine [H+] [H+] = 10 (-pH)
[H+] = 10 (-9.86)
[H+] = 1.38 X 10 -10 M11Created by Seth Floyd - What's on Your
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Sample Problem 3
What is the pH of a solution with a [OH-] = 2.35 X 10-9?1st determine pOH pOH = -log [OH-]
pOH = -log[2.35X10-9 M]pOH = 8.63
2nd determine pH pH = 14 – pOHpH = 14- 8.63pH = 5.37 (acidic)
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Sample Problem 4
What is the pH of a solution that was made from 4.57g of HCl dissolved in 750 mL of water?
1st determine moles of HCl
4.57g HCl
36.46 g HCl1 mol HCl = 0.125 mol
HCl
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Sample 4 ….
2nd determine concentration of [H+], since this is an acid the [H+] would be the same as the concentration of the whole molecule of HCl. We will get [H+] & [Cl-], both with the total of 0.125 moles each.
So concentration will be moles / volume (L)[H+] = 0.125 moles/ 0.750 L
[H+] = 0.333M
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Problem 4…
Next determine pHpH = -log [H+]
pH = -log [0.333M]pH = 0.48 (very acidic)
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Your Turn..
1. What is the [H+] of an acid with a pH of 5.56?2. Determine the pH of a 0.0045 M HCl?3. Determine pOH of a solution with a pH of 8.65?4. What is the pH of a base with an [OH-] of 3.44X10-5
M?Ans: 1. 1.35
2. 2.75X 10-6M
3. 5.35
4. 9.5416Created by Seth Floyd - What's on Your
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