Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H...
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Transcript of Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H...
![Page 1: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/1.jpg)
Acids, Bases, &
SaltsChapter 20Lesson 1
![Page 2: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/2.jpg)
What is an ACID?• pH less than 7• Neutralizes bases• Forms H
+ ions in solution
• Corrosive-reacts with most metals to form hydrogen gas
• Good conductors of electricity
![Page 3: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/3.jpg)
Acids Generate Ions
HNO3 + H2O H3O+ + NO3
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Weak vs. Strong Acids
• Weak Acids do not ionize completely: Acetic, Boric, Nitrous, Phosphoric, Sulfurous
• Strong Acids ionize completely: Hydrochloric, Nitric; Sulfuric, Hydriodic
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Common Acids • HCl- hydrochloric- stomach acid
• H2SO4- sulfuric acid - car batteries
• HNO3 – nitric acid - explosives
• HC2H3O2- acetic acid - vinegar
• H2CO3-carbonic acid – sodas
• H3PO4- phosphoric acid -flavorings
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What is a BASE?
• pH greater than 7• Feels slippery• Dissolves fats and oils• Usually forms OH- ions in
solution• Neutralizes acids
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Weak vs. Strong Bases
• Weak Bases: ammonia; potassium carbonate, sodium carbonate
• Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide; calcium hydroxide
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Common Bases
• NaOH- sodium hydroxide (LYE) soaps, drain cleaner
• Mg (OH)2 - magnesium hydroxide-antacids
• Al(OH)3-aluminum hydroxide-antacids, deodorants
• NH4OH-ammonium hydroxide- “ammonia”
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Types of Acids and Bases
• In the 1800’s chemical concepts were based on the reactions of aqueous solutions.
• Svante Arrhenius developed a concept of acids and bases relevant to reactions in H2O.
• Arrhenius acid – produces hydrogen ions in water.• Arrhenius base – produce hydroxide ions in water.
![Page 10: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/10.jpg)
A broader ,more modern concept of acids and bases was developed later.
Bronsted-Lowry acid- donates a hydrogen ion in a reaction.
Bronsted – Lowry base – accepts a hydrogen in a reaction.
![Page 11: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/11.jpg)
• Conjugate acid- compound formed when an base gains a hydrogen ion.
• Conjugate base – compound formed when an acid loses a hydrogen ion.
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12
BrØnsted-Lowry Acids and Bases
• acids donate a proton (H+).
• bases accept a proton (H+).
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13
Conjugate Acid-Base Pairs
In the reaction of HF and H2O,
• one conjugate acid-base pair is HF/F−.
• the other conjugate acid-base pair is H2O/H3O+.
• each pair is related by a loss and gain of H+.
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14
Learning Check
Write the conjugate base of the following.
1. HBr
2. H2S
3. H2CO3
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15
Solution
Remove H+ to write the conjugate base.
1. HBr Br-
2. H2S HS-
3. H2CO3 HCO3-
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pH Scale
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pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
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Acid – Base Reactions
• A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.
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Reactions with indicators
Indicator Acid color
Neutral color
Base color
Phenolphthalein Colorless Faint pink Dark pink
Bromthymol blue
Yellow Green Blue
Litmus Red ----- Blue
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Kw of Water
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Kw is the ion-product
• Kw is aka dissociation constant of water
• It has been found experimentally that at 25 °C,
• [H+ ]=[OH-] and they both equal 1X10-7M
• Since Kw= [H+ ][OH-] = [1X10-7M]2
• Then Kw = 1X 10-14.
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What does this mean?
• This means that any aqueous solution at 25 ° C, no matter what it (the water) contains, the product of [H+] and [OH-] MUST always equal 1.0 X 10-14.
• There are 3 possibilities:
• A neutral solution where [H+]=[OH-].
• An acid solution where [H+]>[OH-].
• A basic solution where [H+]<[OH-].
![Page 24: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/24.jpg)
In all 3 of the situations:
• Kw = [H+][OH-] = 1.0 X 10-14.
• So in any given aqueous situation, one may calculate the [H+] or [OH-] as required for any solution at 25°C.
• State if Acidic, Basic or Neutral.
• A. 1.0X10-5 M OH- 1.0 X10-9 M H+
• B. 1.0X10-7 M OH- 1.0 X10-7 M H+
• C. 1.0X10-15 M OH- 10.0 M H+
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Answers
• A. Basic
• B. Neutral
• C. Acid
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How to Solve for the [ions]
• Kw = [H+][OH-]
• 1.0 X 10-14= [H+][OH-]
• [H+] = [OH-]/(1.0 X 10-14)
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pH scale is an easy way to represent acidity.
• pH = -log[H+]
• At a neutral solution at 25 °C
• [H+] = [OH-] = (1.0 X 10-14)½ = 1.0 X 10-7
• What is the pH of this?
• pH = -log[H+]
• = -log(1.0 X 10-7)
• Take out you calculator and what do you get?
• 7.00
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Sig Figs in Log problems• The number of sig figs in an original number
equals the number of decimal places in the pH.
• Example:
• If sample is Kw= [H+] = 1.0 X 10-7
• How many sig fig?
• 2
• This pH is …
7.00 2 decimal places for the two sig figs.
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pH vs. pOH
• If pH is = -log [H+]
• Then pOH = -log [OH-]
• And pK = -log K
• Note that pH changes by 1 for every power of 10 in the change of concentration.
![Page 30: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/30.jpg)
Examples
• Calculate the pH and pOH of each• 1.0 X 10-3 M OH-• pOH = 3.00 pH = 11.00• H+ = Kw/[OH-] = (1.0 X 10-14)/(1.0 X 10-3)• = 1.0 x 10-11
• 1.0 M H+ • pH = 0.00 [OH-]=Kw/[H+]= 1.0x10-14/1• pOH = 14
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Remember
• Kw =[H+][OH-]
• And therefore,
• -log K = -log [H+] + -log [OH-]
• log K = log[H+] + log[OH-]
• pKw = pH = pOH therefore
• pH + pOH = 14
• At 25 °C pKw = 14.00 (1.0 X 10-14)
• Thus pH = pOH = 14 at 25 °C
![Page 32: Acids, Bases, & Salts Chapter 20 Lesson 1. What is an ACID? pH less than 7 Neutralizes bases Forms H + ions in solution Corrosive-reacts with most metals.](https://reader030.fdocuments.in/reader030/viewer/2022032803/56649e395503460f94b2a302/html5/thumbnails/32.jpg)
Example Problem
• If the [H+] in a solution is 1.0 x 10-5M, is the solution acidic, basic, or neutral? What is the [OH-] of this solution?