# hw3 - amg2845 hw03 McCord(53580 This print-out should have...

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amg2845 – hw03 – McCord – (53580) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. NOTE: If you see a number with an e in it followed by a signed number, you need to realize that the e means × 10 to the power of what follows. For example.. 3 . 56 e - 07 = 3 . 56 × 10 07 Quest is still being tweaked to properly display scientific notation numbers. Some DO display correctly, while others display via the e notation. 001 10.0 points An equilibrium in which processes occur con- tinuously, with NO NET change, is called 1. static equilibrium. 2. heterogeneous equilibrium. 3. dynamic equilibrium. correct 4. homogeneous equilibrium. Explanation: For a system at dynamic equilibrium, al- though the concentrations of the components do not change, the processes continue to oc- cur in the foward and reverse directions at the same rate. 002 10.0 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 of the substance in its standard state. correct 2. 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 = - RT ln K . 3. They are dimensionless because the pres- sures or concentrations we put in are all for the substances in their standard states. 4. The statement is not true. Equilibrium constants have units that involve some multi- ple of atmospheres or moles per liter. 5. They are dimensionless because concen- trations and pressures have no units. Explanation: The amount of each component is in terms of activity, which is the measured amount (concentration, pressure) divided by the amount of that component in its standard state in that unit. The units in the numera- tor and denominator are identical and cancel out. 003 10.0 points Consider the reaction 2 HgO(s) 2 Hg( ) + O 2 (g) . What is the form of the equilibrium constant K c for the reaction? 1. K c = [Hg] 2 [O 2 ] 2. K c = [O 2 ] [HgO] 2 3. K c = [O 2 ] correct 4. None of the other answers is correct. 5. K c = [Hg] 2 [O 2 ] [HgO] 2 Explanation: Solids and liquids are not included in the K expression. 004 10.0 points The expression for K c for 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. [NH 3 ] 4 [O 2 ] 5 [NO] 4 [H 2 O] 6 3. [NO] 4 [H 2 O ] 6

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amg2845 – hw03 – McCord – (53580) 2 4. [NO] 4 [H 2 O] 6 [NH 3 ] 4 [O 2 ] 5 correct Explanation: The equation must be written with the ap- propriate formula and correctly balanced. K c is the equilibrium constant for species in so- lution and equals the mathematical product of the concentrations of the chemical prod- ucts, divided by the mathematical product of the concentrations of the chemical reactants.
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