# Chapter Eight

 In Hess's law, what can be done with the reactants and the products? added and subtracted When you reverse an equation in Hess' technique, what must happen? change the sign Standard heats of formation: the enthalpy change for the formation of one mole of substance in its standard state from its constituent elements in their standard states True or False: The standard heats of formation are per one mole. False:the standard heats of formation are per whatever mole we were given in the reaction (the limiting reactant) What is the standard heat of formation for any element in its standard staet? zero In Hess' law and standard heats of formation, the reactants are a. positive b. negative b. negative In Hess' law and standard heats of formation, the products are: a. positive b. negative a. positive How can we figure out the standard heat of formation? Products - reactants How can bond dissociation energy be used? to approximate the value for standard heats of formation How do we solve for H with bond dissociation? Reactants- products in bond dissociation the reactants are: a. positve b. negative b. positive In bond dissociation, the reactants are: a. positive b. negative b. negative What is the second law of thermodynamics: reactions proceed in the direction that increases the entropy (S) of the system plus surroundings Spontaneous process one that proceeds on its own without any continous external influence Nonspontaneous process takes place only in the presence of a continuous external influence The measure of molecular disorder in a system is called the system's __; this is __. What are the units? entropy (S)J/K Positive value of dS indicates __. increased disorder Negative value of dS indicates __. decreased disorder In terms of both enthalpy and entropy, explain a spontaneous process? -dH (decrease in enthalpy)+dS (increase in entropy) In terms of both enthalpy and entropy, explain a nonspontaneous process? +dH (increase in enthalpy)-dS (decrease in entropy) Which is favored: spontaneous or nonspontaneous? spontaneous What is Gibb's Free Energy Change? weighs the relative contributions of enthalpy and entrophy to the overall spontaneity of a process When is G spontaneous? when negative When is dG nonspontaneous? when positive When is dG at equilibrium? when 0 What does q symbolize? quantity of heat transferred The higher the heat capacity (C), what? the greater the amount of heat needed to produce a given temperature change AuthorDesLee26 ID188697 Card SetChapter Eight DescriptionAHHHH! Updated2012-12-11T15:42:22Z Show Answers