L23_Thermo2

L23_Thermo2 - EXAM 3 tomorrow: GOOD LUCK! Solutions of...

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EXAM 3 tomorrow: GOOD LUCK!!!
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Solutions of sodium thiosulfate are used to dissolve unexposed AgBr in the developing process for black-and-white film. What mass of AgBr can dissolve in 1.00 L of 0.5 M Na 2 S 2 O 3 ? Assume the overall formation constant for Ag(S 2 O 3 ) 2 -3 is K f = 2.9x10 13 and K sp (AgBr) = 5.0x10 -12 . (1) AgBr(s) <-> Ag + + Br - K sp = 5.0x10 -12 (2) Ag + + 2 S 2 O 3 2- <-> Ag(S 2 O 3 ) 2 -3 K f = 2.9x10 13 (1)+(2) AgBr(s) + 2 S 2 O 3 2- <-> Ag(S 2 O 3 ) 2 -3 + Br - K= K sp * K f =145. Init. 0.5 M 0 0 Change: - y -2 yy y Equil. 0.5 -2 y Solve: y =6.0-24.0 y -> y =0.04 mol/L Molar mass of AgBr=187.8 g/mol Answer: 0.04 mol (7.5g) of AgBr will dissolve in 1.00 L of 0.5 M Na 2 S 2 O 3 . 145 ) 2 5 . 0 ( ] [ ] ][ ) ( [ 2 2 2 3 3 2 3 3 2 = = = y y O S Br O S Ag K 0 . 12 . 145 ) 2 5 . 0 ( = = y y
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The low pH of a 0.01 M aqueous Fe(NO 3 ) 3 solution can be attributed to the presence of the complex ion, Fe(H 2 O) 6 3+ , which acts as a 1. Brønsted-Lowry acid. 2. Brønsted-Lowry base. 3. Lewis base. 4. water ligand donor. 5. none of these .
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Thermodynamics: - can the rxn go at all in a certain direction? - would it be spontaneous under certain conditions? Spontaneous process: can occur by itself without outside intervention once conditions have been established for its initiation.
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This note was uploaded on 07/22/2008 for the course CHEM 115b taught by Professor Reisler during the Spring '08 term at USC.

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L23_Thermo2 - EXAM 3 tomorrow: GOOD LUCK! Solutions of...

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