Chapter 9 Acids and Bases
Strengths of Acids and Bases Making Dilutions
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Strengths of Acids and Bases
Strong acids completely ionize (100%) in aqueous solutions
HCl + H2O
H3O+ + Cl- (100 % ions)
Strong bases completely (100%) dissociate into ions in aqueous solutions. NaOH Na+ (aq) + OH-(aq) (100 % ions)
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NH3, A Bronsted-Lowry Base
When NH3 reacts with water, most of the reactants remain dissolved as molecules, but a few NH3 reacts with water to form NH4+ and hydroxide ion. NH3 + H2O NH4+(aq) + OH- (aq)
acceptor
donor
+
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Strong and Weak Acids and Bases
Strong acids
HCl, HNO3 , H2SO4 Most other acids are weak. Strong bases
NaOH, KOH, and Ca(OH)2 Most other bases are weak.
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Learning Check SW1
Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. ___ HCl (aq) B. ___ NH3(aq)
C. ___ NaOH (aq) D. ___ H2CO3 (aq)
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Solution SW1
Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. _1__ HCl (aq) B. _3__ NH3(aq)
C. _1__ NaOH (aq) D. _2__ H2CO3 (aq)
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Antacids
Used to neutralize stomach acid (HCl) Many contain one or more weak bases
Alka-Seltzer: Di-gel: Gelusil: Maalox: Mylanta: NaHCO3, citric acid, and aspirin CaCO3 and Mg(OH)2 Al(OH)3 and Mg(OH)2 Al(OH)3 and Mg(OH)2 Al(OH)3 and Mg(OH)2
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More Antacids
Milk of Magnesia: Rolaids: Mg(OH)2
AlNa(OH)2CO3 aluminum sodium dihydroxy carbonate
Tums:
Tempo:
CaCO3
CaCO3, Al(OH)3, Mg(OH)2
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Dilutions
Add water Volume increases. New concentration is less than initial
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Concentration of A Diluted Solution
A 25 mL sample of a 6.0 M KOH is diluted by adding 75 mL of water. Calculate the new concentration of the KOH solution. Moles KOH = 0.025 L x 6.0 moles = 0.15 moles 1L New volume = 25 mL + 75 mL = 100. mL = 0.100 L New molarity = 0.15 moles = 1.5 M 0.100 L
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Learning Check SW 2
A 125 mL sample of a 3.0 M HCl is diluted by adding 250 mL of water. The new concentration of the HCl solution is 1) 8.0 M 2) 1.5 M 3) 1.0 M
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Solution SW 2
3) 1.0 M
moles HCl = 0.250 L x 3.0 moles = 0.75 mole 1L new M = 0.75 mole 0.750 L
(new volume)
1.0 M HCl
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Learning Check SW 3
A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % 2) 7.5 % 3) 10. %
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Learning Check SW 3
A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % g sucrose = 50.0 mL x 15 g sucrose = 7.5 g 100 mL new % = 7.5 g sucrose = 3.0 % sucrose 250 mL
(new volume)
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