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Chem 30 > Chapter 9 > Flashcards

Chapter 9 Flashcards

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1
Q

what is the law of conservation of energy

A

during physical and chemical processes energy may change form but it cannot be created or destroyed

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2
Q

if a chemical system gains energy the surroundings ______

A

lose energy

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3
Q

if a chemical system loses energy the surroundings _______

A

gain energy

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4
Q

what is exothermic

A

energy/heat exit the chemical system

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5
Q

what is endothermic

A

energy/heat enter the chemical system

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6
Q

what does exothermic result in

A

results in a decrease in chemical potential energy

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7
Q

what does endothermic result in

A

results in an increase in chemical potential energy

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8
Q

sign for exothermic

A

negative

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9
Q

sign for endothermic

A

positive

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10
Q

exothermic graph and where to label reactants and products

A

starts up (label reactants) and goes down (label products)

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11
Q

endothermic graph

A

starts down (label reactants) and goes up (label products)

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12
Q

what are the axis labelled in endo and exothermic graphs

A

x=reaction pathway

y=potential energy

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13
Q

Thermochemical equation for exothermic and description

A

A+B ——> C+D+ triangle H

energy is on PRODUCT side

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14
Q

Thermochemical equation for endothermic and description

A

A+B + triangle H —>C+D

energy is on REACTANT side

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15
Q

exothermic equation with triangle H notation

A

A+B—->C+D triangle H-_______

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16
Q

endothermic equation with triangle H notation

A

A+B—->C+D triangle H+_____

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17
Q

what is energy

A

the ability to do work

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18
Q

what is kinetic energy

A

energy of motion

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19
Q

what is potential energy

A

stored energy

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20
Q

what is heat

A

transfer of thermal energy

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21
Q

description of molecules in a temp change

A

gain or lose energy and move faster or slower

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22
Q

3 types of molecular motion

A

translational

rational

vibrational

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23
Q

what is chemical potential energy

A

energy stored in the bonds of a substance and relative intermolecular force

24
Q

what is thermal energy

A

total kinetic energy of all of the particles of a system

25
Q

what has more thermal energy a big or small object and why

A

a big object because it has more mass

26
Q

what does temp do to thermal energy

A

increases it

27
Q

thermal energy formula and units

A

Q=mctraingleT

Q= J
m= g
c=
T= degrees celsius

28
Q

what is temperature

A

measure of the average kinetic energy of the particles in a system

29
Q

lower heat capacity means (in terms of temp)

A

higher final temp

30
Q

heat is not ______ by a system but is _________

A

heat is not possessed by a system but is energy flowing between systems

31
Q

what is specific heat capacity

A

quantity of energy required to raise the temp of one gram of a substance by one degree

32
Q

what is the density of water

A

1.00kg/L

33
Q

mass formula in terms of density and volume

A

mass=density(volume)

34
Q

what is calorimetry

A

technological process of measuring energy changes of an isolated system using a calorimeter

35
Q

what does a calorimeter involve

A

a thermometer
stopper
2 styrofoam cups containing reactants in solution

36
Q

calorimetry process (2 steps)

A

chemical is placed or dissolved in water

energy transfers between the chemical system and the surrounding way (is monitored by measuring changes in water temp)

37
Q

exothermic example

A

hot pack

38
Q

endothermic example

A

cold pack

39
Q

calorimetry assumptions (list 5)

A

all energy is gained or lost by the calorimeter

all material is conserved

assume dilute solutions have the same properties of water

thermal energy gained or lost by the rest of the system is negligible

pressure remains constant in solutions and flame calorimetry

40
Q

what is enthalpy

A

total kinetic and potential energy within a chemical system (energy possessed by system)

41
Q

how is enthalpy communicated

A

the difference in enthalpy between react and and products

42
Q

what is molar enthalpy

A

change in enthalpy expressed per mole of a substance undergoing a specific reaction

43
Q

molar enthalpy formula and units

A

H= triangle H/n

H=(KJ per mol)

triangle H= Kj

44
Q

molar enthalpy steps

A

1) write a balance question

2) determine knowns and unknowns
- make sure H is per mol
- divide by moles if not

3) find moles using unit analysis
4) solve for unknown using molar enthalpy formula
5) concert to desired units

45
Q

molar enthalpy calorimetry steps

A

1) determine Q using thermal energy formula (combine both masses)
2) determine triangle H assuming triangle H= -Q
3) determine moles using unit analysis or concentration formula
4) determine molar enthalpy using molar enthalpy formula

46
Q

flame calorimetry steps

A

same as molar enthalpy calorimetry

47
Q

bomb calorimetry steps

A

1) write knowns and unknowns

2) determine unknown using Qcal=C(triangle t)

48
Q

formula for bomb calorimetry

A

Qcal=C(triangle t)

49
Q

thing to remember for final answer with molar enthalpy

A

may have to determine if endo or exothermic and indicate with plus or negative sign

50
Q

molar enthalpy: finding n

A

1) steps 1 and 2 the same

2) skip to step 4

51
Q

molar enthalpy: finding mass

A

1) steps 1 and 2 the same

2) skip to step 4 and 5

52
Q

molar enthalpy calorimetry: finding mass

A

1) steps 1 and 2 the same
2) determine moles using molar enthalpy formula
3) concert to mass

53
Q

molar enthalpy: finding Qcal/ Q any other total

A

1) determine Qcal using

Qcal= Qcan + Qwater

54
Q

molar enthalpy: finding c

A

1) use mc(triangle t) 1 =-
mc(triangle t) 2

and manipulate for unknown c

55
Q

flame calorimetry: finding t

A

1) determine moles of compound using unit analysis
2) determine triangle H using molar enthalpy formula
3) determine triangle t using - triangleH= Qcan + Qwater and manipulate for two t’s.

56
Q

flame calorimetry: finding H using Qcal

A

1) determine Qcal using
Qcal= Qcan + Qwater

2) steps 2-5 the same

57
Q

bomb calorimetry: heat combustion per gram

A

1) steps 1 and 2 the same
2) divide Q by mass
3) state value as KJ/g or J/g

Chem 30 (6 decks)

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