Vandenbout Worksheet 4

Vandenbout Worksheet 4 - € € WorkSheet 4 Equilibrium 1....

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Unformatted text preview: € € WorkSheet 4 Equilibrium 1. For the following equilibrium CH 3COOH( aq) ↔ CH 3COO− ( aq) + H + ( aq) if K = 1.8 x 10‐5 at what [H+] concentration will there be equal concentrations of CH3COOH and CH3COO‐? 2. For the following reaction 3 Fe2O3( s) ↔ 2 Fe( s) + O2 ( g) 2 ΔRH° = +825.5 kJ mol‐1 ΔRG° = +742.2 kJ mol‐1 What is K for this reaction at 25°C? Given that air is 21% O2, what is Q for this reaction in air? Assuming that ΔRH° and ΔRS° are independent of temperature, approximate at what temperature Fe2O3 would first start to form any Fe in air. 3. True/False Decide if each statement is true or false and write out an explanation. For the following reaction an increase in the total pressure will lead to an increase in the equilibrium constant A( g) + 2 B( g) ← → C ( g) For endothermic reactions, increasing the temperature will increase the equilibrium constant. Adding reactants to an equilibrium mixture will lower the equilibrium constant For the following reaction, Kp= Kc A( g) + B( g) ← → 2C ( g) € € 4. The following reaction is exothermic and has a KP = 1.9 x 10‐4 at 400°C N 2 ( g) + 3H 2 ( g) ← → 2 NH 3 ( g) € which direction (if any) will the reaction have to shift toward to get back to equilibrium after the following changes (assume the change listed is the only change. i.e. increase in temperature at constant pressure) Explain your answer briefly. Increase in the total pressure by compressing the volume Increase the temperature Add 1 mol N2, 3 mol H2, and 2 mol NH3 Increase the total pressure by adding 2 moles of He gas at constant volume 5. (note: this problem involves finding ΔRH° and ΔRS°) Calcium carbonate can decompose into calcium oxide and carbon dioxide by the following reaction. CaCO3 ( s) ← → CaO( s) + CO2 ( g) Given the data below What is K for this reaction at 298 K? What would K be at 500 K? If 20 g of CaCO3 were placed in an evacuated container. What would the partial pressure of CO2 be in the container at equilibrium at 500 K if there is still some solid CaCO3 remaining? All data at 298K (you can assume H and S are independent of T) Compound ΔfH° (kJ mol‐1) ΔfG° (kJ mol‐1) S°(J K‐1 mol‐1) CaCO3 (s) ‐1207 ‐1129 93 CaO (s) ‐635 ‐604 40 CO2 (g) ‐393.5 ‐394.5 213.5 6. (10 points) For the reaction A( g) + 2 B( g) ← → C ( g) At some temperature you find PA = 0.5 atm PB = 0.25 atm Pc = 1.5 atm What is KP at this temp? Is ΔRG° positive negative or zero at this temperature? Explain. Do you think this reaction is exothermic or endothermic? Is there any way to tell? If the total pressure was changed to 4 atm, Would the number of moles of C increase, decrease, or stay the same? Would Kp increase, decrease, or stay the same? € € € You must get down your stoichiometry. Answer the following 7. For this reaction 2 SO2 ( g) + O2 ( g) ↔ 2 SO3 ( g) You initially have concentration of SO2 of 0.1 M, and O2 of 0.5 M At equilibrium you find you have a concentration of SO3 of .09 M. € How much SO2 and O2 do you have at equilibrium? 8. For this reaction A( s) ↔ B( g) + 2C ( g) If you start out with only solid A, what is the ratio of the partial pressures of B to C at equilibrium? If the partial pressure of B is found to be 0.01 atm at 298K, what is ΔRG°? 9. Practice Practice Practice Write down the equilibrium constants for the following reactions Make RICE diagrams for each assuming you start with either 1M concentrations of gases or some amount of pure solid. Set up the algebra for how you would solve for the equilibrium concentrations (you can’t do the algebra since you don’t have the Ks) 2 NH 3 ( g) + CO2 ( g) ↔ N 2CH 4 O( g) + H 2O( g) 2 NBr3 ( g) ↔ N 2 ( g) + 3Br2 ( g) 2KClO3 ( s) ↔ 2KCl( s) + 3O2 ( g) CuO( s)+ H 2 ( g) ↔ Cu( l) + H 2O( g) € ...
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