#Chem 162-2008 homework 5th week

#Chem 162-2008 homework 5th week - Hill & Petrucci...

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th Week Equilibrium Constant Relationships 31. If the equilibrium concentrations in the reaction 2A(g) + B(g) C(g) are [A] = 2.4 x 10 -2 M, [B] = 4.6 x 10 -3 M, and [C] = 6.2 x 10 -3 M, calculate the value of K c . Kc = ([C]/([A] 2 x [B])) = ([6.2x10 -3 ]/([2.4x10 -2 ] 2 x [4.6 x 10 -3 ])) = 2.34 x 10 3 37. In the reaction N 2 O 4 (g) 2NO 2 (g), equilibrium is reached at a temperature at which P NO2 = 3 (P N2O4 ) 1/2 . What must be the value of K p at this temperature? N 2 O 4 (g) 2NO 2 (g) Initial Change Equilibrium X 3(X 1/2 ) K = [NO 2 ] 2 /[N 2 O 4 ] = ((3(X 1/2 )) 2 )/X = 9X/X = 9 LeChâtelier’s Principle 43. The water-gas reaction is used to produce combustible gases from carbon (coal) and steam. C(s) + H 2 O(g) CO(g) + H 2 (g) K p = 9.7 x 10 -17 at 298K ∆H o = 131kJ What will be the effect on the final equilibrium amount of H 2 (g) if a gaseous mixture originally at equilibrium with a large excess of C(s) at 298K is subjected to the following changes: (a) more H 2 O(g) is added; (b) a catalyst is added; (c) the mixture is transferred to a reaction vessel of greater volume; (d) more CO(g) is added; (e) an inert gas is added to the reaction vessel to increase the total pressure; (f) the temperature is raised to 1000K; (g) a small amount of C(s) is removed? C(s) + H 2 O(g) + ∆ CO(g) + H 2 (g) (a) The reaction would go to the right, so more H 2 would be formed. (b) A catalyst has no effect on the equilibrium constant, so there would be no change in [H 2 ]. (c) If it’s greater volume, then it’s lower pressure. Lower pressure would push the reaction to the right (increasing the [H 2 ]) in order to raise the pressure. (d) More CO would shift the equilibrium to the left, decreasing the [H 2 ]. (e) An inert gas has no effect. (f) If the temperature is raised, the reaction would shift to the right raising the [H 2 ]. (g) Changing the amount of C would have no effect on the equilibrium expression. 47. In the formation of the following gaseous compounds from their gaseous elements, identify the reactions that occur to a greater extent at high pressures and the reactions that are unaffected by the total pressure: (a) NO(g) from N 2 (g) and O 2 (g), (b) NH 3 (g) from N 2 (g) and H 2 (g), (c) HI(g) from H 2 (g) and I 2 (g), (d) H 2 S(g) from H 2 (g) and S 2 (g)? 1
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(a) N 2 (g) + O 2 (g) 2NO(g) Increasing the pressure would have no effect on the reaction, since there are two moles of gas on each side of the equilibrium sign, so there is no way to alleviate the increase in pressure. (b) N 2 (g) + 3H 2 (g) 2NH 3 (g) Increasing the pressure would cause the reaction to go to the right, since there are two moles of gas on the right and four moles of gas on the left, so the reaction going to the right would alleviate the increased pressure. (c) H
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#Chem 162-2008 homework 5th week - Hill & Petrucci...

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