a2s-1 - Chemistry 2000 Spring 2001 Section B Assignment 2...

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Unformatted text preview: Chemistry 2000 Spring 2001 Section B Assignment 2 Solutions 1. Since this is a liquid, the mole fractions are the appropriate measures of activity. Fortunately, we are given the data in exactly the right form: If 6.42% of the molecules are in the chair form Xchair 0 0642. Moreover, the rest (93.58%) must be in the boat form, i.e. Xboat 0 9358. The equilibrium constant is ¡ ¡ a2 NOBr aNO 2 aBr2 £ ¡ £ ¡ £¥ ¤ £¥ ¤ £ £ ¢ ¡ ¢ ¢ £ ¥ ¢¤ ¢ ¢ ¢£ ¢ Q PNOBr P 2 PNO P 2 PBr2 P 0 969 2 0 105 2 0 400 213 ¡ ¡ 2. We need to determine the reaction ratio Q: 14 6 0 9358 0 0642 ¡ Xboat Xchair aboat achair ¡¡ K Since Q is larger than K , there is excess product. Accordingly, NOBr will react to form NO and bromine. (a) We can solve this problem by working out how the initial and final pressures are related: ¦¡ ¡§ 0 § PCOCl2 ¡ ¡ ¦¡ ¡¡ ¦¢ ¡ ¢ PCOCl2 ¢ 0 20 aCOCl2 aCO aCl2 ¢£ K 03 PCOCl2 (atm) 0 PCOCl2 ¡ ¡¨ ¡¦ ¡¨ ¡ £ ¦ £ ¦ ¡ ¢£ ££ £ ¥ £ ¢ ¢¢ For this reaction, PCl2 (atm) 0.3 0 3 PCOCl2 PCOCl2 P PCO PCl2 PCOCl2 PCOCl2 0 3 PCOCl2 2 0 20 0 3 PCOCl2 0 018 0 12PCOCl2 2 0 20PCOCl2 2 0 20PCOCl2 1 12PCOCl2 5 58 or 0 016 atm 0 018 § § Only the second solution makes any physical sense. Thus, PCOCl2 1 ¡ PCO (atm) initial 0.3 final equilibrium 0 3 PCOCl2 ¦¡ 3. 0 016 atm. (b) 3 mol £ aH2 CO3 aCO2 aH2O ¢£ ¢ § K £  ¡ 4. £  ¡ ¢ £¢ ¡ ¢ £ ¡ ¢ ¨ £ ¡ ©¢ ¡¢ n ¢£ T ¤ V £ P PV RT 0 016 atm 101 325 Pa atm 1633 Pa 3 1m 10 L 0 01 m3 1000 L 600 273 15 K 873 K 1633 Pa 0 01 m3 2 2 10 8 314 510 J K 1mol 1 873 K n We are given K and the pressure of carbon dioxide (from which we can easily compute its activity). We want to solve for the activity of H2 CO3 (from which we can obtain the concentration). We still need to know the activity of the solvent, i.e. its mole fraction. § aH2 CO3  H2 CO3 K aCO2 aH2O 10 10 5 3 36 mol L 2 8 33 mol 0 31 0 31 mol 33 Pa 10 2 101 325 Pa   ¡ £ ¡ ¢  ¡ XH2 O ¤  ¡ £   ¡ ¢ £ ¢£ ¢ ¡ ¨©¡ ¨ ¡  ¨ ¨ ¡ ¡ ¤ ¡ ¡ ¡ ¤ nNaCl 150 g 8 33 mol 18 0152 g mol 18 g 0 31 mol 58 443 g mol nH2 O nH2 O nNa nCl 8 33 nH2 O 0 931 0 931 10 10 5 § § ...
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This note was uploaded on 03/03/2012 for the course CHEM 2000 taught by Professor Roussel during the Fall '06 term at Lethbridge College.

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