Chapter 5 - Thermochemistry

0.0(0)
studied byStudied by 0 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/38

encourage image

There's no tags or description

Looks like no tags are added yet.

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

39 Terms

1
New cards

thermal energy

results from motion of molecules

2
New cards

heat

amount of energy transferred between substances

3
New cards

exothermic

energy releasing -

4
New cards

endothermic

energy requiring +

5
New cards

temperature

average kinetic energy of the particles in a sample of matter

6
New cards

opne system

matter and energy can change

7
New cards

closed system

mattter can’t change but energy can

8
New cards

isolated systen

neither matter nor energy can change

9
New cards

bomb vs cup calorimeter

bomb measures combustion and has water not directly in contact with the system

10
New cards

molar enthalpy

enthalpy chnage per mole of a reaction (h=nh^o)

11
New cards

what are thr 3 calorimeter assumptions

no heat transferred to environment

any heat absorbed or released by the cal is negligable

a dilute solution has heat capacity and density of water

12
New cards

thermochemical equation

represent enthalpy of reaction within the equation

13
New cards

method 2 of representing H: beside equation

negative for exo positive for endo, and in kJ/mol

14
New cards

standard molar enthalpy of reaction

Standard molar enthalpies allow chemists to create tables to compare enthalpy values. ° "nought" represents enthalpy change of a chemical reaction

that occurs at SATP (25°C and 100 kPa)

15
New cards

enthalpy

shows E(kJ) over the reaction progress

16
New cards

state function

path independant; change in altitude relys only on the difference between start and end

17
New cards

hess’s law

H can be written in steps and is equal to the sum of the enthalpy of each individual step

18
New cards

using the 3rd means of showing enthalpy

use a balanced equation of formation for exact;y 1 mol of the compound of interest. then enthaply = ehtalpy products - enthalpy reactants

  • must add standard states to equation as well

19
New cards

enthalpy of elements in standard state

in standard state, the enthalpy of a substance is just 0. eg o2, Na, Cl2

20
New cards

exmaples of potential energies

bond energy, nuclear pe of protons and neutrons

21
New cards

exmaples of kinetic energy

motion of elections, vibrations, rotations and translation of atoms and molecules

22
New cards

enthalpt change: physical change

10^0-10² kj/mol overcoming intermolecular force; particles remain unchanges

23
New cards

enthalpy change, chemical change

10² - 10^4 kJ/mol. overcoming electronic structure + bonds; new substance with nre bonds eg combustion

24
New cards

enthalpy change: nuclear change

10^10 - 10^12 kj/mol. overcome forces between protons and nucleus; new atoms form eg nuclear decay

25
New cards

spontaneous reaction

given the necessary activation energy, proceeds without continuous assitance on an open system

26
New cards

non- spontaneous

contiuous supply of energy is needed to sustain the reaction

27
New cards

what is entropy

disorder or randomness, entropy increases when disorder increases; S = Sproducts - Sreactants

28
New cards

predicting entropy

s is positive when there is increasing disorder (volume increases, temp increase, state change from less movement to more, more moles of products than reactants, mixing/dissolving,complex molecule being broken down)

29
New cards

first law of thermodynamics

total e in the universe is constant, e is not created nor destroyed, but can be transfered or transformed

30
New cards

second law of thermodyanmics

total entropy of the universe is constantly increases. suniverse = ssystem+ssurrounding

31
New cards

if Suniverse is positive

a process is spantaneous in the direction written

32
New cards

if SUniverse is negative

a process is spantanrous in the oppsoite direction than written

33
New cards

if SUniverse = 0

no tendancy to occur and system at equilibrium

34
New cards

entropy of a reaction:

sum of products - sum of reactants

35
New cards

gibbs free energy

energy available to do useful work. DECREASES when a reaction is spantaneous (negative for spontaneous)

36
New cards

G>0

spantenous for reverse reaction

37
New cards

G<0

spantaneous as written

38
New cards

G=0

no reaction

39
New cards

equation for gibs free energy (h-TS) uses… for temp

kelvins (273k+C)