Unit 9 - Thermodynamics Flashcards by Jack Corston

State the first law of thermodynamics

Energy can not be created or destroyed it can only be transferred or converted from one form to another

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What is the internal energy

All of the energy that is in a closed system

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What is the equation for internal energy

Define the terms of this equation

Delta U = q + w

q = heat added to the system (J)
W = work done J

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If W is positive what does this mean

Work is done to the system

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If W is negative what does this mean

The system does wrk

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What is the equaion for work done by a system

Define the terms

W = - Pext x deltaV

Pext = 1.01x10^5
V = volume

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What is temperature

A measure of the avaerage kinetic energy of the atoms or molecules in the system

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q =

Mc delta T

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Define the terms of q = mcdeltaT

q= heat 
m = mass
c = specific heat capacity 
T = temp

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What is the specific heat capacity

Energy required to raise 1kg of a substance by 1 deg

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What is Cm / Cmol

The energy required to raise 1 mole of a substance by 1 degree

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Work doene is

Movement against a force

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Eqn for work done

W=fd

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What happens when a gas does work

Increase in volume and work done is negatice

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What happens when work is done on a gas

Decrease in the volume and work done on a gas is positive

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What is the equation for Pressur

P = FA

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What is the equation for work relating pressure, area and displacement

Work = Pressure x Area X Displacement

Work = P X Change in volume

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Molecules always move toward a

lower energy state

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Equation for enthalpy

Define the terms

H = U + PV

H = enthalpy 
U = internal energy 
P = pressure 
V = volume

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Hess’s Law states …

The total enthalpy change for a chemical reaction does not depend on the pathway it takes, it only depends on the initial and final states

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What is the standard enthalpy change of formation

Ammount of heat lost or gained when one mole of a compound is formed from its consitiuent elements

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Exothermic –>

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Heat is released

Increase in the temperature of the surroundings

Endothermic –>

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Heat is absorbed

Temperature of the surroundings decreases

What is bond enthalpy

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The energy it takes to break one mole of bonds in the gaseous phase

Breaking a bond ...

Always requires energy

Making a bond ...

Always releases energy

Define entropy

The ammount of dissorder in a system

A box with 8 balls has ________ entropy than a box of 6 balls

What is the second law of thermodynamics `

Any spontaneous reaction will increase the disorder of the universe

An increase in entropy during a reaction means that

Products are more disordered than the reactants

What is Gibbs Free Energy

Is the ammount of energy in a system that is available to do useful work

What is the free energy of an element in its standard state

Delta G =

Delta H - T . Delta S ``` G = free energy H = enthalpy T = absolute temp (K) S = entopy ```

If delta H is greater than T delta S ...

reaction is enthalpy driven

If T delta S is greater than delta H ...

Reaction is entropy drive

How spontaneous is the following reaction Delta H is less than 0 AND Delta S is greater than zero

Reaction is spontaneous at all values of T (T can only be positive)

Delta S =

Delta S products - delta S reactants

Negative delta S means

Entropy is higher in the reactants than the products Order is increasing --> DECREASE IN DISORDER

How spontaneous is the following reaction Delta H is less than 0 AND Delta S is less than 0

Spontanous only a low values of T When TdeltaS is SMALL

How spontaneous is the following reaction Delta H is greater than 0 Delta S is greater than 0

Spontaneous at large values of TdeltaS | When TdeltaS is large

How spontaneous is the following reaction Delta H is greater than 0 AND Delta S is less than 0

Non spontaneous at all values of T | deltaG > 0

If deltaS is positive this means ... give an example of whn this would be the case

Positive value of deltaS when entropy increases Example when we have more moles of gaseous products than reactants

what happens when deltaH is positive

Energy is released in the form of heat

If delta G < 0 this means

Spontaneous

If delta G > 0 this means

Not spontaneous in the forward direction

A spontaneous reaction is AKA

Exergonic

A non spontanous reaction AKA

Endeegonic

At G=0 the system is as

equilibrium

What does adiabatic mean

No heat is added or taken away

equation for delta S in terms of heat and temperature

Delta S = Q/T ``` Q = heat T = temperature ```

All spontanous reactions are

Irreversible

Give another equation for delta G Define the terms of this eqn

Delta G = Delta G0 + RTlnQ Q = reaction quotient, eqbm contant before the reaction has reached eqbm

How would you determine Q

COnc products / conc reactants

Unit 9 - Thermodynamics Flashcards

(53 cards)