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General Chemistry Principles, Patterns, and Applications, 2011

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2. For each equilibrium reaction, describe how Q <strong>and</strong> K change when the pressure is decreased, the<br />

temperature is increased, the volume of the system is decreased, <strong>and</strong> the concentration(s) of the reactant(s)<br />

is increased.<br />

a. 2A g<br />

( ) B( g) DH = -80 kJ / mol<br />

b. A( g) 2B( g) DH = 0.3 kJ / mol<br />

c. 2A( g) 2B( g) + C( g) DH = 46 kJ / mol<br />

3. Le Châtelier’s principle states that a system will change its composition to counteract stress. For the system<br />

system CO g<br />

( ) + C CO( g) + Cl2( g) COCl2 g<br />

( ), write the equilibrium constant<br />

expression K p . What changes in the values of Q <strong>and</strong> K would you anticipate when (a) the volume is doubled,<br />

(b) the pressure is increased by a factor of 2, <strong>and</strong> (c) COCl 2 is removed from the system?<br />

4. For the equilibrium system 3O2 g<br />

( ) 2O3 g<br />

( ), ΔH° = 284 kJ, write the equilibrium constant<br />

expression K p . What happens to the values of Q <strong>and</strong> K if the reaction temperature is increased? What<br />

happens to these values if both the temperature <strong>and</strong> pressure are increased?<br />

5. Carbon <strong>and</strong> oxygen react to form CO 2 gas via C s<br />

( ) + O2( g)<br />

CO2 g<br />

( ), for which K = 1.2 × 10 69 .<br />

Would you expect K to increase or decrease if the volume of the system were tripled? Why?<br />

6. The reaction<br />

COCl2 g<br />

( ) CO( g) + Cl2( g) has K = 2.2 ´ 10 -10 at 100°C.<br />

Starting with an initial PCOCl2 of 1.0<br />

7. atm, you determine the following values of P CO at three successive time intervals: 6.32 × 10 −6 atm,<br />

1.78 × 10 −6 atm, <strong>and</strong> 1.02 × 10 −5 atm. Based on these data, in which direction will the reaction proceed after<br />

each measurement? If chlorine gas is added to the system, what will be the effect on Q?<br />

8. The following table lists experimentally determined partial pressures at three temperatures for the reaction<br />

Br2 g<br />

( ) 2Br g<br />

( ).<br />

T (K) 1123 1173 1273<br />

PBr2 ( atm) 3.000 0.3333 6.755 × 10 −2<br />

PBr (atm)<br />

3.477 × 10 −2 2.159 × 10 −2 2.191 × 10 −2<br />

9. Is this an endothermic or an exothermic reaction? Explain your reasoning.<br />

10. The dissociation of water vapor proceeds according to the following reaction<br />

: H2O g<br />

( ) 12O2( g) + H2 g<br />

( ). At 1300 K, there is 0.0027% dissociation, whereas at 2155 K, the<br />

dissociation is 1.18%. Calculate K <strong>and</strong> K p . Is this an endothermic reaction or an exothermic reaction? How do<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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