Chapter 2: The First Law

Question 1

The total energy of a system is..

Answer 1

constant

Question 2

open system

Answer 2

matter can be transferd

can exchange energy

Question 3

closed system

Answer 3

matter can not be transfered through a boundary

can exchange energy

can transfer energy to the surrounding if they are at a lower temptaure

Question 4

isolated system

Answer 4

neither energy ot matter can be transfered

energy trasnfer making use of thermal motion in the surrounding

Question 5

work

Answer 5

is done to achive motion aginst an opposing force

the transfer of energy that makes use of orgainzed motion in the surroundings

Question 6

energy

Answer 6

the capacity to do work ,if you are able to move against an opposing force then you can do work

compression in creases the capacity to do work , i.e. the energy of the system is increased . i.e work is done on the system

when work is done on the system the energy of the system increases and its capacity to do work is increased

when the system does work , the energy of the system decreases and the systems capacity to do work is decreased

Question 7

heat

Answer 7

when the energy of a system changes as a result of temperature difference between the system and its surrounding, the energy has been transfered as heat

heat is a process ( the transfer of energy as a result of temperature difference ) , not an entity

Question 8

diathermic

Answer 8

boundaries that permit the transfer of heat as energy

Question 9

exothermic process

Answer 9

releases hate to the surrounding

▲H<0

Question 10

adiabatic

Answer 10

boundaries that do not permit the transfer of energy as heat

Question 11

endothermic process

Answer 11

energy is aquired from the surrounding as heat

energy is tranferd as heat to the system from the surroundings

▲H > 0

Question 12

thermal motion

Answer 12

the disorderly motion of molecules

heating is the transfer of energy that makes us of disorderly, random, molecuar motion in the surroundings

Question 13

internal energy

Answer 13

total energy of a system ( kinetic + potential energy)

∆U = U_f -U_i

dU = dq + dw_exp + dw_e

Question 14

state function

Answer 14

depend only on the curren state of the systen and is independt of how that state has been prepared

path indepedent

extensive property( depends on the amount of substance

measure in joule: 1 J = kg m² s^-2

molar internal energy (U_m = U/n) is an intensive(indepednt of amount) property

Question 15

First Law of thermaldynamics (2A.2)

Answer 15

▲U = q +w

Question 16

expansion work (2A.5a) (2A.6)

Answer 16

work arising from change in volume

neg cahnges in volume (compression)

dw = -p_ex dV

Pa m³

w = -p_ex▲V (constant pressure)

Question 17

free expansion

Answer 17

expanson against zero opposing force

p_ex = 0

w = 0

vacuum

Question 18

reversible expansion (2A.8a)

Answer 18

dw = - p_ex dV = - pdV

Question 19

calorimetry

Answer 19

the study of the energy tranfer as heart during physical and chemical processes

Question 20

calorimeter

Answer 20

a device used to energy transfer as heat

Question 21

adiabatic bomb calorimeter

Answer 21

q_{v is measued}

q = C▲T

where C is the calorimeter constant

Question 22

heat capacity (2A.14)

Answer 22

slope of internal energy vs, tmeperature

C_v = (∂U/∂T)_v

molalr heat capacity C_v,m = C_v /n

specifit heat capacity C_v,s = C_v/m

where m is mass

Cp = (∂H/∂T)p

Question 23

enthalpy

Answer 23

H = U + pV

state function

increase with temp

▲H = q_p = C_p▲T

perfect gas: H = U + pv = U + nRT

perfect gas , isothermal:▲H = ▲U + ▲n_gRT

Question 24

standard state

Answer 24

of a substance at aspecified temperature is its pure form at 1 bar

Question 25

standard enthalpy of transition of vaporixation

Question 26

standard enthalpy of fusion

Question 27

Born-Haber Cycle

Question 28

thermochemical equation

Question 29

standard reaction enthalpy

Answer 29

▲_rH^⦵ =Σ vH_m^⦵-ΣvH_m^⦵

Question 30

Hess’s Law

Answer 30

the standard enrhalpy of an overall reaction is the sum of the standard enthalpies of the individual reactions into which a reaction may be divded

Question 31

Standard Enthalpy of Formation

Question 32

Mean bond enthalpies

Question 33

Path Function

Question 34

isenthalpic

Question 35

internal pressure

Question 36

Joule-Thomson effect

Question 37

a process does work if ….

Answer 37

in principle it can be harnessed to rise a weight someeher in the surrounding

ex. expansion of a gas , the motion of the pistion be used to raise a weight

Question 38

an endothermic process in a diathermic contaniner

Answer 38

(a boundary that does perrmit the tranfer of energy as hate)results in energy flowing into the system as heat to restore the temperature to that of the surrounding

a,) energy enters as heat from the surrounfoundings , and the system remains at the same temp(isothermal)

Question 39

an exorhernic process in a diathermic container results in

Answer 39

a release of energy as heat to the surroundings

energy leaves as hate and the process os isothermal

Question 40

exothermic process in a adiabatic container

Answer 40

the rise in temp

Question 41

endothemic process in a adiabatic system

Answer 41

the temperature falls

Question 42

why is the distincation of work and heat made in the surrounding

Answer 42

it is a refercne point

compression : the order atom of the weight(surroundings) creates random motion in the system( an increased in thermal motion)

we observe, the orderly decent of atoms and report that work is being done even though it is stimulating thermal motion

Question 43

What are the modes of motion

Answer 43

tanslational

rotate

vibrate

Question 44

equipartition theorem

Answer 44

can be used to predict the contribution of each mode of motion of a molecule to the total energy of a collection of non interacting molecules

Question 45

translational and rotational modes of motion are porpportional to temperature

i.e internal energy incres with temp

Question 46

the internal energy of a perfect gas is

Answer 46

independent of the volume it occupies

i.e. there aare no intermoleacular interactions in a perfect gas, so the distance between the molceules has no effect on the energy

Question 47

heat and work are equalent was of

Answer 47

transering internal energy

Question 48

in an isolated system intenal energy is (first law of thermodynamic )

Answer 48

constant

▲U = q + w

q- energy transfered as heat =0

w-work =0

the change in internal energy is equal to the energy that passes throught its boundary as heat or work

Question 49

sign of ▲U

Answer 49

pos if heat or work enter the system

neg, if energy is transferd out aas heat or work

Question 50

isothermal expanson of a perfect gas

Answer 50

w = -nRT dV/V = -nRTlnV_f/V_i

Question 51

Heat transfered at constant volume

Answer 51

dU = dq

no expansion work

▲U = q_v

Question 52

internal energy at constant volume

Answer 52

▲U = q_v = C_v ▲T

Question 53

a change in enthalpy is equal to

Answer 53

the energy transfered as heat as constant pressure

Question 54

relation between heat capacties

Answer 54

C_p - C_v = nR