1178564611Xuj - Anderson, Kiel Homework 3 Due: Feb 18 2007,...

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Anderson, Kiel – Homework 3 – Due: Feb 18 2007, midnight – Inst: McCord 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page – fnd all choices be±ore answering. The due time is Central time. 001 (part 1 o± 1) 10 points An equilibrium in which processes occur con- tinuously, with NO NET change, is called 1. dynamic equilibrium. correct 2. heterogeneous equilibrium. 3. static equilibrium. 4. homogeneous equilibrium. Explanation: For a system at dynamic equilibrium, al- though the concentrations o± the components do not change, the processes continue to oc- cur in the ±oward and reverse directions at the same rate. 002 (part 1 o± 1) 10 points Explain why equilibium constants are dimen- sionless. 1. Every concentration or pressure that en- ters into K c or K p is really divided by the cor- responding concentration or pressure o± the substance in its standard state. correct 2. They are dimensionless because concen- trations and pressures have no units. 3. They are not really dimensionless but we must treat them as such in order to be able to take ln K in the expression Δ G 0 = - R T ln K . 4. They are dimensionless because the pres- sures or concentrations we put in are all ±or the substances in their standard states. 5. The statement is not true. Equilibrium constants have units that involve some multi- ple o± atmospheres or moles per liter. Explanation: The amount o± each component is in terms o± activity, which is the measured amount (concentration, pressure) divided by the amount o± that component in its standard state in that unit. The units in the numera- tor and denominator are identical and cancel out. 003 (part 1 o± 1) 10 points Consider the reaction 2HgO(s) * ) 2Hg( ) + O 2 (g) . What is the ±orm o± the equilibrium constant K c ±or the reaction? 1. None o± the other answers is correct. 2. K c = [O 2 ] [HgO] 2 3. K c = [Hg] 2 [O 2 ] 4. K c = [Hg] 2 [O 2 ] [HgO] 2 5. K c = [O 2 ] correct Explanation: Solids and liquids are not included in the K expression. 004 (part 1 o± 1) 10 points The expression ±or K c ±or the reaction at equi- librium is 4 NH 3 (g) + 5 O 2 (g) * ) 4 NO(g) + 6 H 2 O(g) 1. [NH 3 ] 4 [O 2 ] 5 2. [NO]
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This note was uploaded on 03/20/2008 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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1178564611Xuj - Anderson, Kiel Homework 3 Due: Feb 18 2007,...

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