Chemical Reaction and Equilibrium Expression

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CHAPTER 18 REVIEW

Chemical Equilibrium
SECTION 18-1
SHORT ANSWER
1.

Answer the following questions in the space provided.

Silver chromate dissolves in water according to the following equation:
→ 2Agϩ(aq) ϩ CrO42Ϫ(aq)
Ag2CrO4(s) ←
Which of these correctly represents the equilibrium expression for the above equation?
2[Agϩ] ϩ [CrO 42Ϫ]
[Agϩ]2[CrO42Ϫ]
[Ag2CrO4]
(a) ᎏᎏ
(b) ᎏ
ᎏ
(c)
ᎏ
ᎏ
1
Ag2CrO4
[Agϩ]2[CrO42Ϫ]

[Agϩ]2[CrO42Ϫ]
(d) ᎏᎏ
2[Ag2CrO4]

2. Are pure solids included in equilibrium expressions? Explain your answer.

3. Write the equilibrium expression for the following hypothetical equation:
→ 2C(aq) ϩ 3D(aq)
3A(aq) ϩ B(aq) ←

4. a. Write the appropriate equilibrium expression for each of the following equations. Include the value of K.
→ 2NO2(g)
(1) N2O4(g) ←
K ϭ 0.1

Ϫ
→ NHϩ
(2) NH4OH(aq) ←
4 (aq) ϩ OH (aq)

MODERN CHEMISTRY
HRW material copyrighted under notice appearing earlier in this work.

K ϭ 2 ϫ 10Ϫ5

SECTION 18-1 REVIEW

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SECTION 18-1 continued

→ Pb2ϩ(aq) ϩ 2IϪ(aq)
(3) PbI2(s) ←

K ϭ 7 ϫ 10Ϫ9

→ 2H2O(l)
(4) H3Oϩ(aq) ϩ OHϪ(aq) ←

K ϭ 1 ϫ 1014

b. Which of the four systems in part a proceeds farthest to the right when equilibrium is established?
c. Which system contains mostly reactants at equilibrium? PROBLEMS provided. 5.

Write the answer on the line to the left. Show all your work in the space
Consider the following reaction:
→ 2NO2(g)
2NO(g) ϩ O2(g) ←
At equilibrium, [NO] ϭ 0.80 M, [O2] ϭ 0.50 M, and [NO2] ϭ 0.60 M.
Calculate the value of K for this reaction.

6. Nitrous acid is a weak acid that hydrolyzes according to the following equation:
→ H3Oϩ(aq) ϩ NOϪ2 (aq)
HNO2(aq) ϩ H2O(l ) ←
At 298 K, K ϭ 4.3 ϫ 10Ϫ4.
a. Which term in the above equation does not appear in the equilibrium expression? b. For the above reaction, [H3Oϩ] ϭ [NOϪ2 ] ϭ 0.043 M at equilibrium.
Calculate [HNO2].

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SECTION 18-1