Strong And Weak Acids And Bases

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) LecturePLUS Timberlake

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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

+

acceptor

H2O

NH4+(aq)

+ OH- (aq)

donor

+

+ LecturePLUS Timberlake

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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. LecturePLUS Timberlake

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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) LecturePLUS Timberlake

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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) LecturePLUS Timberlake

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Antacids Used to neutralize stomach acid (HCl) Many contain one or more weak bases Alka-Seltzer:

NaHCO3, citric acid, and aspirin

Di-gel:

CaCO3 and Mg(OH)2

Gelusil:

Al(OH)3 and Mg(OH)2

Maalox:

Al(OH)3 and Mg(OH)2

Mylanta:

Al(OH) Mg(OH)2 3 and LecturePLUS Timberlake

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More Antacids Milk of Magnesia: Rolaids:

Mg(OH)2

AlNa(OH)2CO3 aluminum sodium dihydroxy carbonate

Tums:

CaCO3

Tempo:

CaCO3, Al(OH)3, Mg(OH)2 LecturePLUS Timberlake

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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 LecturePLUS Timberlake

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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

1.0 M HCl

(new volume)

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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) LecturePLUS Timberlake

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