Acid-base equilibrium pH scale, weak acids bases, salt of weak acid and bases.
The Chemistry of Acids and Bases. Acid and Bases.
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Transcript of The Chemistry of Acids and Bases. Acid and Bases.
The Chemistry of The Chemistry of Acids and BasesAcids and BasesThe Chemistry of The Chemistry of Acids and BasesAcids and Bases
Acid and BasesAcid and Bases
Acid and BasesAcid and Bases
Acid and BasesAcid and Bases
Acids
Have a sour taste. Vinegar is a solution of acetic acid. CitrusHave a sour taste. Vinegar is a solution of acetic acid. Citrusfruits contain citric acid.fruits contain citric acid.
React with certain metals to produce hydrogen gasReact with certain metals to produce hydrogen gas..
React with carbonates and bicarbonates to produce carbon React with carbonates and bicarbonates to produce carbon dioxide gasdioxide gas
Have a bitter taste.Have a bitter taste.
Feel slippery. Many soaps contain bases.Feel slippery. Many soaps contain bases.
Bases
Some Properties of Acids
Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion
attached to a water molecule)
Taste sour
Corrode metals
Electrolytes
React with bases to form a salt and water
pH is less than 7
Turns blue litmus paper to red “Blue to Red A-CID”
Some Properties of Bases
Produce OHProduce OH-- ions in water ions in water
Taste bitter, chalkyTaste bitter, chalky
Are electrolytesAre electrolytes
Feel soapy, slipperyFeel soapy, slippery
React with acids to form salts and waterReact with acids to form salts and water
pH greater than 7pH greater than 7
Turns red litmus paper to blue “Basic Blue”Turns red litmus paper to blue “Basic Blue”
Some Common Bases
NaOHNaOH sodium hydroxidesodium hydroxide lyelye
KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap
Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics
Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia
Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)
Acid/Base definitions
• Definition #1: Arrhenius (traditional)
Acids – produce H+ ions (or hydronium ions H3O+)
Bases – produce OH- ions
(problem: some bases don’t have hydroxide ions!)
Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
Acid/Base Definitions
• Definition #2: Brønsted – Lowry
Acids – proton donor
Bases – proton acceptor
A “proton” is really just a hydrogen atom that has lost it’s electron!
A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor
acid conjugate base
base conjugate acid
Conjugate PairsConjugate Pairs
Learning Check!
Label the acid, base, conjugate acid, and Label the acid, base, conjugate acid, and conjugate base in each reaction:conjugate base in each reaction:
HCl + OHHCl + OH-- Cl Cl-- + H + H22OO HCl + OHHCl + OH-- Cl Cl-- + H + H22OO
HH22O + HO + H22SOSO44 HSO HSO44-- + H + H33OO
++ HH22O + HO + H22SOSO44 HSO HSO44-- + H + H33OO
++
The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases. Instead of acids and bases. Instead of using very small numbers, using very small numbers, we just use the NEGATIVE we just use the NEGATIVE power of 10 on the Molarity power of 10 on the Molarity of the Hof the H++ (or OH (or OH--) ion.) ion.
Under 7 = acidUnder 7 = acid 7 = neutral 7 = neutral
Over 7 = baseOver 7 = base
pH of Common SubstancespH of Common Substances
Calculating the pH
pH = - log [H+](Remember that the [ ] mean Molarity)
Example: If [H+] = 1 X 10-10
pH = - log 1 X 10-10
pH = - (- 10)pH = 10
Example: If [H+] = 1.8 X 10-5
pH = - log 1.8 X 10-5
pH = - (- 4.74)pH = 4.74
Try These!Try These!
Find the pH of these:Find the pH of these:1) A 0.15 M solution of 1) A 0.15 M solution of
Hydrochloric acidHydrochloric acid2) A 3.00 X 102) A 3.00 X 10-7-7 M M
solution of Nitric acidsolution of Nitric acid
pH calculations – Solving for pH calculations – Solving for H+H+pH calculations – Solving for pH calculations – Solving for H+H+
If the pH of Coke is 3.12, [HIf the pH of Coke is 3.12, [H++] = ???] = ???
Because pH = - log [HBecause pH = - log [H++] then] then
- pH = log [H- pH = log [H++]]
Take antilog (10Take antilog (10xx) of both) of both sides and get sides and get
1010-pH -pH == [H[H++]][H[H++] = 10] = 10-3.12-3.12 = 7.6 x 10 = 7.6 x 10-4-4 M M *** to find antilog on your calculator, look for “Shift” or “2*** to find antilog on your calculator, look for “Shift” or “2nd nd function” and function” and
then the log buttonthen the log button
pH calculations – Solving for H+pH calculations – Solving for H+• A solution has a pH of 8.5. What is the A solution has a pH of 8.5. What is the
Molarity of hydrogen ions in the solution?Molarity of hydrogen ions in the solution?
pH = - log [HpH = - log [H++]]
8.5 = - log [H8.5 = - log [H++]]
-8.5 = log [H-8.5 = log [H++]]
Antilog -8.5 = antilog (log [HAntilog -8.5 = antilog (log [H++])])
1010-8.5-8.5 = [H = [H++]]
3.16 X 103.16 X 10-9-9 = [H = [H++]]
pH = - log [HpH = - log [H++]]
8.5 = - log [H8.5 = - log [H++]]
-8.5 = log [H-8.5 = log [H++]]
Antilog -8.5 = antilog (log [HAntilog -8.5 = antilog (log [H++])])
1010-8.5-8.5 = [H = [H++]]
3.16 X 103.16 X 10-9-9 = [H = [H++]]
pOH• Since acids and bases are opposites, pH Since acids and bases are opposites, pH
and pOH are opposites!and pOH are opposites!• pOH does not really exist, but it is pOH does not really exist, but it is
useful for changing bases to pH.useful for changing bases to pH.• pOH looks at the perspective of a basepOH looks at the perspective of a base
pOH = - log [OHpOH = - log [OH--]]Since pH and pOH are on opposite ends,Since pH and pOH are on opposite ends,
pH + pOH = 14pH + pOH = 14
[OH[OH--] and pH] and pHWhat is the pH of the What is the pH of the
0.0010 M NaOH solution? 0.0010 M NaOH solution?
[OH-] = 0.0010 (or 1.0 X 10[OH-] = 0.0010 (or 1.0 X 10-3-3 M) M)
pOH = - log 0.0010pOH = - log 0.0010
pOH = 3pOH = 3
pH = 14 – 3 = 11pH = 14 – 3 = 11
The pH of rainwater collected in a certain region of the northeastern United States on a particular day was 4.82. What is the H+ ion concentration of the rainwater?
The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?
[OH[OH--]]
[H[H++]] pOHpOH
pHpH
1010 -pOH-pOH
1010 -pH-pH-Log[H
-Log[H ++]]
-Log[OH
Log[OH --]]
14 - pOH
14 - pOH
14 - pH
14 - pH
1.0 x 10
1.0 x 10-
14-14
[OH[OH
-- ]]
1.0 x 10
1.0 x 10-
14-14
[H[H++ ]]
Calculating [H+], pH, [OH-], and pOH
Problem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 3.0 M and (b) 0.0024 M. Calculate the pH, [OH-], and pOH of the two solutions at 25°C.
Problem 2: What is the [H+], [OH-], and pOH of a solution with pH = 3.67? Is this an acid, base, or neutral?
Problem 3: Problem #2 with pH = 8.05?