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Chapter 17
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Most reactions do not proceed to completion. N 2 (g) + H 2 (g) 2NH 3 (g) 2NH 3 (g) N 2 (g) + H 2 (g)
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Equilibrium is when the concentrations of the reactants and products of a chemical reaction are constant. Chemical equilibrium happens when the rate of the forward reaction is equal to the rate of the reverse reaction.
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aA + bB cC + dD The equilibrium constant expression: If K eq > 1 the products are favored If K eq < 1 the reactants are favored
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Homogeneous: CO 2 (g) 2CO(g) + O 2 (g) Heterogeneous: H 2 O(l) H 2 O(g) CaCO 3 (s) CaO(s) + CO 2 (g)
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Write the equilibrium constant expression fo the following reactions N 2 (g) + H 2 (g) 2NH 3 (g) N 2 O 4 (g) 2NO 2 (g) 2H 2 S(g) 2H 2 (g) + S 2 (g) CO(g) + 3H 3 (g) CH 4 (g) + H 2 O(g) 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g)
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When equilibrium is reached the concentrations of the reactants and the products will not change. At any given temperature the value of k eq will always be the same no matter what the equilibrium concentrations are.
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Calculate the value of k eq for the following reaction and concentrations. N 2 + 3H 2 2NH 3 [N 2 ] = 0.533 M [H 2 ] = 1.600 M [NH 3 ] = 0.933 M 0.399
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Calculate k eq for the reaction: N 2 O 4 (g) 2NO 2 (g) If [N 2 O 4 ] = 0.0185 mol/L and [NO 2 ] = 0.0627 mol/L Calculate k eq for the reaction CO(g) + 3H 2 (g) CH 4 (g) + H 2 O(g) if [CO] = 0.0613 mol/L, [H 2 ] = 0.1839 mol/L, [CH 4 ] = 0.0387 mol/L and [H 2 O] = 0.0387 mol/L For the reaction COCl 2 (g) CO(g) + Cl 2 (g)
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The by-products of an industrial process are CO and H 2. These two gasses can combine to produce CH 4 and H 2 O in equilibrium. Use the following data to find k eq for this reaction. [CO] = 0.300M, [H 2 ] = 0.100M, [CH 4 ] = 0.059 M, [H 2 O] = 0.020 M The chemists in charge of this industrial process would like to make use of the methane (CH 4 ) that is being produced. In order for them to have a usable amount of methane the concentration must be 0.100 M or higher. How can they achieve this?
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If a stress is applied to a system at equilibrium, the system will shift in the direction that relieves that stress. Suppose additional CO is injected into the reaction vessel of the industrial process we discussed. How would this affect the equilibrium of the system?
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Along with adding reactants or removing products, what other stresses can we apply to a system? Temperature Pressure
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The reaction: CO(g) + 3 H 2 (g) CH 4 (g) + H 2 O(g) Has a K eq of 3.933 at 1200 K. If the [CO] = 0.850 M, [H 2 ] = 1.33 M, and [H 2 O]= 0.286 M, what is the concentration of CH 4 ?
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Some ionic compounds dissolve completely in water. Ex: NaCl(aq) Na + (aq) + Cl - (aq) Some ionic compounds do not dissolve completely in water. Ex: BaSO 4 (s) Ba 2+ (aq) + SO 4 2- (aq) This process is happening in equilibrium. So there is an equilibrium constant associated with it.
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Calculate the solubility of AgI(s). k sp = 8.5 x 10 -17
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Examples Calculate the solubility in mol/L of CuCO 3 if it’s k sp is 2.5 x 10 -10 1.6 x 10 -5 mol/L Calculate the solubility PbCrO 4 if it’s k sp is 2.3x10 -13. 4.8 x 10 -7 mol/L Calculate the solubility of CaF 2 if it’s k sp is 3.5x10 -11. 4.18x10 -6 mol/L
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Sometimes the concentrations of the ions are not the same as the solubility. Mg(OH) 2 (s) Mg 2+ (aq) + 2OH - (aq) k sp = 5.6 x 10 -12
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