Spontaneity of Reactions

Description

using entropy and enthaply to discuss the spontaneity of a reaction
Tanya Haywood
Flashcards by Tanya Haywood, updated more than 1 year ago
Tanya Haywood
Created by Tanya Haywood almost 9 years ago
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Resource summary

Question Answer
Whether a reaction is spontaneous is dependent on the changes in which two concepts? entropy and enthalpy
Entropy is a measure of disorder
Increasing entropy comes from an increase in the amount of substance an increase in the amount of gases melt, boil or sublime a substance
Increasing the temperature of a system does what to the entropy? it increases the entropy
if enthalpy change is positive compare the relative enthalpy of the reactants with the products the reactants have less enthaply than the products
if enthaply change is positive describe what you would feel as the reaction proceeds the system would feel colder
Sponaneity is favoured with what change in enthaply? when the enthaply change is negative (exothermic reaction)
Describe an exothermic reaction One where the reactants have more enthalpy than the products; the change in enthaply is negative; energy is released; the temperature of the system increases (it gets hotter)
spontaneous or not? Entropy increases and enthaply change is negative always spontaneous
spontaneous or not? Entropy decreases and enthaply change is negative it depends (likely to be spontaneous at low temp)
spontaneous or not? Entropy increases and enthaply change is positive it depends (likely to be spontaneous at high temp)
spontaneous or not? Entropy decreases and enthaply change is positive not spontaneous (ever)
exo or endo?? endothermic
why is this endothermic? the reactants have less enthalpy than the products heat is absorbed the enthalpy change is postive
which state changes are exothermic? gas to liquid liquid to solid gas to solid
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