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GAMSAT (SIII) - Physics > Unit 9 - Thermodynamics > Flashcards

Unit 9 - Thermodynamics Flashcards

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1
Q

State the first law of thermodynamics

A

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

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2
Q

What is the internal energy

A

All of the energy that is in a closed system

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3
Q

What is the equation for internal energy

Define the terms of this equation

A

Delta U = q + w

q = heat added to the system (J)
W = work done J
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4
Q

If W is positive what does this mean

A

Work is done to the system

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5
Q

If W is negative what does this mean

A

The system does wrk

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6
Q

What is the equaion for work done by a system

Define the terms

A

W = - Pext x deltaV

Pext = 1.01x10^5
V = volume
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7
Q

What is temperature

A

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

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8
Q

q =

A

Mc delta T

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9
Q

Define the terms of q = mcdeltaT

A 
q= heat 
m = mass
c = specific heat capacity 
T = temp
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10
Q

What is the specific heat capacity

A

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

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11
Q

What is Cm / Cmol

A

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

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12
Q

Work doene is

A

Movement against a force

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13
Q

Eqn for work done

A

W=fd

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14
Q

What happens when a gas does work

A

Increase in volume and work done is negatice

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15
Q

What happens when work is done on a gas

A

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

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16
Q

What is the equation for Pressur

A

P = FA

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17
Q

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

A

Work = Pressure x Area X Displacement

Work = P X Change in volume

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18
Q

Molecules always move toward a

A

lower energy state

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19
Q

Equation for enthalpy

Define the terms

A

H = U + PV

H = enthalpy 
U = internal energy 
P = pressure 
V = volume
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20
Q

Hess’s Law states …

A

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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21
Q

What is the standard enthalpy change of formation

A

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

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22
Q

Exothermic –>

A

Heat is released

Increase in the temperature of the surroundings

23
Q

Endothermic –>

A

Heat is absorbed

Temperature of the surroundings decreases

24
Q

What is bond enthalpy

A

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

25
Q

Breaking a bond …

A

Always requires energy

26
Q

Making a bond …

A

Always releases energy

27
Q

Define entropy

A

The ammount of dissorder in a system

28
Q

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

A

More

29
Q

What is the second law of thermodynamics `

A

Any spontaneous reaction will increase the disorder of the universe

30
Q

An increase in entropy during a reaction means that

A

Products are more disordered than the reactants

31
Q

What is Gibbs Free Energy

A

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

32
Q

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

A

0

33
Q

Delta G =

A

Delta H - T . Delta S

G = free energy 
H = enthalpy
T = absolute temp (K)
S = entopy
34
Q

If delta H is greater than T delta S …

A

reaction is enthalpy driven

35
Q

If T delta S is greater than delta H …

A

Reaction is entropy drive

36
Q

How spontaneous is the following reaction

Delta H is less than 0 AND
Delta S is greater than zero

A

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

37
Q

Delta S =

A

Delta S products - delta S reactants

38
Q

Negative delta S means

A

Entropy is higher in the reactants than the products

Order is increasing –> DECREASE IN DISORDER

39
Q

How spontaneous is the following reaction

Delta H is less than 0 AND
Delta S is less than 0

A

Spontanous only a low values of T

When TdeltaS is SMALL

40
Q

How spontaneous is the following reaction

Delta H is greater than 0
Delta S is greater than 0

A

Spontaneous at large values of TdeltaS

When TdeltaS is large

41
Q

How spontaneous is the following reaction

Delta H is greater than 0 AND
Delta S is less than 0

A

Non spontaneous at all values of T

deltaG > 0

42
Q

If deltaS is positive this means …

give an example of whn this would be the case

A

Positive value of deltaS when entropy increases

Example when we have more moles of gaseous products than reactants

43
Q

what happens when deltaH is positive

A

Energy is released in the form of heat

44
Q

If delta G < 0 this means

A

Spontaneous

45
Q

If delta G > 0 this means

A

Not spontaneous in the forward direction

46
Q

A spontaneous reaction is AKA

A

Exergonic

47
Q

A non spontanous reaction AKA

A

Endeegonic

48
Q

At G=0 the system is as

A

equilibrium

49
Q

What does adiabatic mean

A

No heat is added or taken away

50
Q

equation for delta S in terms of heat and temperature

A

Delta S = Q/T

Q = heat 
T = temperature
51
Q

All spontanous reactions are

A

Irreversible

52
Q

Give another equation for delta G

Define the terms of this eqn

A

Delta G = Delta G0 + RTlnQ

Q = reaction quotient, eqbm contant before the reaction has reached eqbm

53
Q

How would you determine Q

A

COnc products / conc reactants

GAMSAT (SIII) - Physics (20 decks)

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