Quiz 2 Enthalpy-solutions

Quiz 2 Enthalpy-solutions - Version 061/AADDB – Quiz 2...

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Unformatted text preview: Version 061/AADDB – Quiz 2 Enthalpy – lyon – (51155) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 1 2 3 4 5 6 7 AA AB AC AD BA BB BC 8 9 10 BACK NEXT BD CA CB CC CD Red = incorrect answer Blue = correct answer Greenish-brown = already answered question You must select CD followed by E (enter) to move to the next question. 001 10.0 points Using Hess’s Law, calculate the ΔH f for NO 2 (g) from its elements in their standard state. NO(g)-→ 1 2 N 2 (g) + 1 2 O 2 (g) Δ H ◦ =- 90 . 25 kJ / mol NO(g) + 1 2 O 2 (g)-→ NO 2 (g) Δ H ◦ =- 57 . 07 kJ / mol 1.- 24 . 77 kJ / mol 2.- 46 . 21 kJ / mol 3. +33 . 18 kJ / mol correct 4. +71 . 65 kJ / mol 5.- 10 . 52 kJ / mol Explanation: Hess’s Law tells us that when reactants are converted to products, the change in enthalpy is the same whether the reaction occurs in one step or in a series of steps. Enthalpy is a state function and only depends on the initial and final state of the reactants and products. The enthalpy change would be the same whether the overall reaction takes place in one step or a series of steps. Therefore, we can determine the enthalpy of formation of NO 2 by the following method: 1) Write the chemical equation for the forma- tion of NO 2 from its elements in their stan- dard states....
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This note was uploaded on 12/13/2011 for the course CH 204 taught by Professor Leytner during the Fall '08 term at University of Texas.

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Quiz 2 Enthalpy-solutions - Version 061/AADDB – Quiz 2...

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