University College - Chemistry Chem 112A Study Guide - Quiz Guide: Enthalpy, Heat Capacity

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ivorykoala623

14 Aug 2018

School

WUSTL

Department

University College - Chemistry

Course

University College - Chemistry Chem 112A

Professor

Bleeke John

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Document Summary

Kirchoff"s law: h t2 = h t1 + cp(t2-t1: used to calculate an enthalpy at a specific heat using the . H of a reaction at a different state. H (molar enthalpy) = n(bonds breaking) n(bonds formed) Enthalpy of formation: formation of 1 mole of molecule from elements in standard states: standard states: most stable form of the pure element at 1 atm and 298 k. Molar enthalpy: enthalpy associated with breaking 1 mol of bonds in gas phase. Enthalpy of atomization: enthalpy change associated with creating. 1 mol gas phase from element in standard state. Enthalpy of reaction: enthalpy change for chemical reaction in which all reactions & products are in standard state. Hess"s laws: add h (enthalpy) of reactions for overall new reaction (since it"s a state function path doesn"t matter)

Related Questions

Chemical energy is released or absorbed from reactions in various forms. The most easily measurable form of energy comes in the form of heat, or enthalpy. The enthalpy of a reaction can be calculated from the heats of formation of the substances involved in the reaction:

?H?rxn=? np?H?f(products)?? nr?H?f(reactants)

where n represents the stoichiometric coefficients.

Calculate the standard enthalpy change for the reaction

2A+B?2C+2D

Use the following data:

Substance	?H?f (kJ/mol)
A	-247
B	-413
C	213
D	-475

?H?rxn =

The oxidation of hydroquinone by hydrogen peroxide in an aqueousenvironment produces quinone and water: C6H4(OH)2(aq) + H2O2(aq)-> C6H4O2(aq) + 2H2O(l) Other related reactions and theircorresponding reaction enthalpies are:

1. C6H4(OH)2(aq) -> C6H4O2(aq) + H2(g)

2. H2(g) + O2(g) -> H2O2(aq)

3. H2(g) + (1/2)O2(g) -> H2O(g)

4. H2O(g) -> H2O(l)

1. ÎH = 177.4 kJ/mol
2. ÎH = -191.2 kJ/mol

3. ÎH = -241.8 kJ/mol

4. ÎH = -43.8 kJ/mol

1. (a) What is the enthalpy change of reaction of the oxidationof hydroquinone by hydrogen peroxide in an aqueous environment, asgiven above? 1. (b) Is the oxidation reaction of hydroquinone byhydrogen peroxide endothermic or exothermic? Briefly justify youranswer in one or two sentences by referring to Îqp of the reaction.-2- 1. (c) What is the standard molar enthalpy of formation ofH2O2(aq)? What is the standard molar enthalpy of formation ofH2O(l)? 1. (d) The enthalpy of an O=O bond is 499 kJ/mol. Using theinformation given, estimate the bond enthalpy of the O-O bond inH2O2(aq). The bonds in H2O2 are: H-O-O-H.

University College - Chemistry Chem 112A Study Guide - Quiz Guide: Enthalpy, Heat Capacity

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