MU #1 Behavior of many acids and bases can be explained by the Arrhenius theory. Arrhenius acids yield H⁺(aq), hydrogen ion as the only positive ion in an aqueous solution. The hydrogen ion may also be written as H₃O⁺(aq), hydronium ion.

Example

HCl(l) dissociates in water

HCl(aq) -->  H⁺(aq) +  Cl^- (aq)  

or

HCl(l) + H₂O(l) -->  H₃O⁺(aq) +  Cl^- (aq)  

Note: In the solution H⁺ reacts with H₂O to produce H₃O⁺ (H⁺ + H₂O -->  H₃O⁺)

Example

H₂SO₄(l) dissociates in water

H₂SO₄(aq) ---> 2 H⁺(aq) +  SO₄^2- (aq)  

or

H₂SO₄(l) + 2 H₂O(l) -->  2 H₃O⁺(aq) +  SO₄^2- (aq)  

Note:  For CO₂ the reaction is as follows

CO₂(g) + H₂O(l) ---> H₂CO₃(aq) ---> 2 H⁺(aq) + CO₃^2-(aq)

Problems

Write the dissociation reactions for the remaining acids in table K

MU #2 Arrhenius bases yield OH^- (aq), hydroxide ion as the only negative ion in an aqueous solution.

Example

NaOH(s) dissociates in water

NaOH(aq) --> Na⁺(aq) + OH^-(aq)

or

NaOH(s) + H₂O(l) --> Na⁺(aq) + OH^-(aq) + H₂O(l)

Note: For NH₃ the reaction is as follows

NH₃(l) + H₂O(l) ---> NH₄⁺(aq) + OH^-(aq)

Problems

Write the dissociation reactions for the remaining bases in table L

Salts form cations (positive ions) other than H⁺ and anions (negative ions) other than OH^- in aqueous solutions.

Example

NaCl(aq) --> Na⁺(aq) + Cl^- (aq)

KC₂H₃O₂(aq) --> K⁺(aq) + C₂H₃O₂^-(aq)

Problems

Find all the salts in table I

MU #3 An electrolyte is a substance which, when dissolved in water, forms a solution capable of conducting an electric current. The ability of a solution to conduct an electric current depends on the concentration of ions. Salts, Arrhenius acids and bases are electrolytes.

Example 

TEST YOUR UNDERSTANDING

1/07

30 Which ion is the only negative ion produced by an Arrhenius base in water?    (1) NO₃^–                 (2) Cl^–                     (3) OH^–                   (4) H^–

6/07

25 An Arrhenius base yields which ion as the only negative ion in an aqueous solution? (1) hydride ion (2) hydrogen ion (3) hydronium ion  (4) hydroxide ion

48 Which two formulas represent Arrhenius acids? (1) CH₃COOH and CH₃CH₂OH (2) HC₂H₃O₂ and H₃PO₄ (3) KHCO₃ and KHSO₄ (4) NaSCN and Na₂S₂O₃

8/07

26 Which formula represents a hydronium ion?    (1) H₃O⁺     (2) NH₄⁺     (3) OH^–   (4) HCO₃^–

27 Which compound is an Arrhenius acid? (1) H₂SO₄      (2) KCl    (3) NaOH      (4) NH₃

2002-6

1. Which ion is produced when an Arrhenius base is dissolved in water?

(1) H⁺ as the only positive ion in solution      (3) OH^- as the only negative ion in solution

(2) H₃O⁺ as the only positive ion in solution (4) H^- as the only negative ion in solution

2.  A substance that conducts an electrical current when dissolved in water is called

            (1) a catalyst        (2) a metalloid     (3) a nonelectrolyte     (4) an electrolyte

8/04

Which substance is an Arrhenius acid?  (1) LiF(aq)   (2) HBr(aq)   (3) Mg(OH)₂(aq)  (4) CH₃CHO

1/03

Which species can conduct an electric current? (1) NaOH(s)  (2) CH₃OH(aq)    (3) H₂O(s)   (4) HCl(aq)

6/03

1. An Arrhenius acid has

        (1) only hydroxide ions in solution  (3) hydrogen ions as the only positive ions in solution

        (2) only hydrogen ions in solution  (4) hydrogen ions as the only negative ions in solution

29. Which 0.1 M solution contains an electrolyte? (1) C₆H₁₂O₆(aq)  (2) CH₃COOH(aq) (3) CH₃OH(aq) (4) CH₃OCH₃(aq)

8/03

29 A sample of Ca(OH)₂ is considered to be an Arrhenius base because it dissolves in water to yield
        (1) Ca²⁺ ions as the only positive ions in solution (3) OH^- ions as the only negative ions in solution
        (2) H₃O⁺ ions as the only positive ions in solution (4) H^- ions as the only negative ions in solution

1/04

26 According to the Arrhenius theory, when a base dissolves in water it produces
        (1) CO₃²⁺ as the only negative ion in solution (2) OH^- as the only negative ion in solution
        (3) NH₄⁺ as the only positive ion in solution (4) H⁺ as the only positive ion in solution

27 Which compound is an electrolyte? (1) C₆H₁₂O₆ (2) CH₃OH (3) CaCl₂ (4) CCl₄

6/04

28 Which pair of formulas represents two compounds that are electrolytes?
        (1) HCl and CH₃OH     (2) HCl and NaOH     (3) C₅H₁₂ and CH₃OH     (4) C₅H₁₂ and NaOH

29 Hydrogen chloride HCl, is classified as an Arrhenius acid because it produces
    (1) H⁺ ions in aqueous solution (2) Cl^- ions in aqueous solution (3) OH^- ions in aqueous solution (4) NH₄⁺ ions in aqueous solution

8/04

27 Which compound is an Arrhenius base? (1) CH₃OH (2) CO₂ (3) LiOH (4) NO₂

28 The only positive ion found in an aqueous solution of sulfuric acid is the

                (1) hydroxide ion (2) hydronium ion (3) sulfite ion (4) sulfate ion

1/05

25 The compound HNO₃ can be described as an

                (1) Arrhenius acid and an electrolyte (2) Arrhenius acid and a nonelectrolyte

                (3) Arrhenius base and an electrolyte (4) Arrhenius base and a nonelectrolyte

6/05

27 Which formula represents an electrolyte?  (1) CH3OCH3        (2) CH3OH            (3) CH3COOH           (4) C2H5CHO 

28 When an Arrhenius acid dissolves in water, the only positive ion in the solution is  (1) H+      (2) Li+    (3) Na+     (4) K+ 

1/06

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