Thermodynamics Exam 1 Flashcards Preview

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Flashcards in Thermodynamics Exam 1 Deck (34)
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1

System

The part of the universe chosen for study

2

Surroundings

Anything that is not defined as the system

3

Boundary

Line or surface that separates the system and surroundings

4

Universe

Composed of both the system and surroundings

5

3 types of systems

Open: exchange of energy and matter can occur across the boundary.

Closed: exchange of energy that can occur across the boundary
Ex: cup with lid

Isolated: no exchange occurs across boundary

6

Kinetic energy (eK)

Translational motion of an object causing energy/energy of a moving object. (V and T)

eK = 1/2 mu^2

7

Potential energy (PE)

Energy due to composition, position, or condition. Stored energy that has potential to do work. (Condition(state), position(height), composition(bond, atom))

8

Thermal energy

Associated with random molecular motion (eg: frictional heating). It is proportional to both the temperature of the system and the number of particles (N) in the system. (Collisions)

9

SI united of joules and Newton’s

J = Nm = kg(m^2/s^2)

N = kg(m/s^2)

10

energy

capacity to do work or produce heat

11

work (w)

force (F) acting over distance (d). W=Fd, V change, or volume change (-P(delta V))

12

Heat (q)

energy transfer between an open or closed system and its surroundings because of a temperature difference between the two.

13

equation for heat

heat = q = mCpT

14

Law of conversation of energy

energy is not created or destroyed

15

q > 0

heat is absorbed by the system. heat enters the system. endothermic (+)

16

q < 0

heat evolves from the system. heat leaves the system. exothermic(-)

17

1 food calorie

1000 calories

18

bomb calorimeter

isolated system at constant volume; highly exothermic reactions occur.

19

chemical energy

energy associated with bonds and intermolecular attraction or repulsion. Potential energy of a system associated with chemistry.

20

heat of reaction (rxn)

quantity of heat exchanged between the system and surroundings during a chemical reaction. Determined by calorimeters. (energy of reaction)

21

coffee cup calorimeter

at constant pressure and commonly used for solutions. there may be numerous sources of q.

22

pressure-volume work (w)

chemical reactions that involve work. if gas is released as a product of a reaction, the gas could exert a force on an external object by pushing it, thereby doing work.

23

1 L atm is how many Joules?

101.325 J

24

First Law of Thermodynamics

Law of conservation of energy, stating that the energy of the universe is constant. This energy is called the total or internal energy (U) which includes both potential and kinetic energy.

25

in an isolated system, what is q and w?

0; bc of no transfer of energy

26

state function

any property that only depends on the current state of the system. the way or path is not relevant. (ex: T,P,V,m,U)

27

path-dependent function

function involves any property that does depend on the pathway by which the current state of the system was obtained. (ex: q and w)

28

Isothermal conditions for ideal gas

T = 0 and U = 0

29

Change in Enthalpy

Delta H which is heat at constant pressure. (no T change)

Equation: delta H = delta U + (P)(delta V)

(Reaction, phase change, mixing solutions, U - w)

30

Temperature

Measure of the kinetic energy of the system (eK)

31

Internal Energy (U)

total amount of energy contained within the system boundary (eK, PE)

32

Hess' Law

technique used to find delta H for a given overall reaction when there is a series of simultaneous reactions each having a given delta H.

Simultaneous reactions: sum up to the overall reaction.
Intermediates: appear in the sim rxns but not in the overall reaction.

33

Standard enthalpy of formation (delta Hf)

change in enthalpy that accompanies the formation of 1 mole of a compound from its elements with all substances in their standard states at 25C. (Elemental form)

Equation: delta H = (sum of (prod moles)(delta H of prod))-(sum of(reactant moles)(delta H of reactants))

34

Important Conditions and Compounds

Gases: H2,N2,O2,F2,Cl2,He
Liquids: Br2,Hg
Solids: I2, C(graphite), Metals