Chapter 6

Created by virgo2 

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Energy, Work, Heat, and Enthalpy

Energy: define

capacity to do work or produce heat

1st law of thermodynamics

energy is conserved

potential E

stored energy

kinetic E

energy due to motion

internal E?

potential+kinetic energies

internal E can be changed by

work and heat

(delta) E =

q + w

Work: define

force applied over a distance

what is w for

an expanding/contracting gas

w =

-P(delta)V

Heat: define

E flow due to temp difference

exothermic

E as heat flows out of a system

endothermic

E as heat flows into a system

How is it measured

chemical reactions = calorimetry

Enthalpy

H

H =

E + PV

State Functions

Yes- Energy (E), Enthalpy (H)

No- Heat, Work (w)

Hess's Law

the change in enthalpy is going from a given set of reactants to a given set of products is the same no matter how many steps it takes

Standard enthalpy of formation

used to calculate (delta) H for a chemical reaction

(delta) H (standard) reaction =

sum of moles of productchange in enthalpy of products -- sum of moles of reactantschange in enthalpy of reactants

path-dependent function

dependent on the amounts given

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