Chemistry Thermochemistry

Question 1

A ___ is the particular part of the universe being studied; everything outside the system is considered the surroundings or environment. A system may be:
Isolated: it cannot exchange energy or matter with the surroundings, as with an insulated bomb reactor
Closed: It can exchange energy but not matter with the surroundings, as with a steam radiator
Open: It can exchange both matter and energy with the surroundings, as with a pot of boiling water

Answer 1

thermodynamic system

Question 2

Properties whose ___ depends only on the initial and final states of the system and not on the path of the change are known as state functions

Answer 2

magnitude

Question 3

___ = delta E sub sys + delta E sub surr = 0

Answer 3

delta E sub univ

Question 4

delta E sys = q (__) + W (work)

Answer 4

heat

Question 5

Reactions that absorb heat energy are said to be ___, while those that release heat energy are said to be exothermic

Answer 5

endothermic

Question 6

q=mcdelta T
The ___ absorbed or released in a given process is calculated from this equation
where m is the mass, c is the specific heat capacity, and delta T is the change in temperature. Specific heat is a property of a material that describes how much energy it takes to raise its temperature

Answer 6

heat

Question 7

___ lost by a system (to its surroundings) or work done by the system (on the surroundings) is considered negative (decreases internal energy

Answer 7

heat

Question 8

delta H rxn = H sub products - H sub reactants
A positive delta H corresponds to an ___ in which enthalpy is added to the system and a negative delta H corresponds to an exothermic process in which the system gives off enthalpy

Answer 8

endothermic process

Question 9

___ occur in systems at constant pressure (delta P = 0). Heat given off or absorbed equals the change in enthalpy of the system.
Isochoric processes occur at constant volume (delta V = 0). Heat given off or absorbed equals the change in internal energy of the system and also equals the change in enthalpy of the system.
Isothermal processes occur when system do not change temperature (delta T = 0). The change in internal energy, as well as enthalpy, equals zero (only for an ideal gas) but head does not equal 0.
Adiabatic processes occur when there is no heat exchanged between systems and their surroundings (delta q = 0). The change in internal energy is equal to work

Answer 9

isobaric processes

Question 10

The ___ of a compound, delta H degree sub f, is the enthalpy change that occurs if one mole of a compound is formed directly from its elements in their standard states

Answer 10

enthalpy of formation

Question 11

Note that the enthalpy of ___ of n element in its standard state is defined as zero, so the heat of formation of a compound gives its increase or decrease in enthalpy from zero

Answer 11

formation

Question 12

Note that the ___ must be balanced for one mole of the product because the enthalpy of formation is defined for one mole of a substance

Answer 12

equation

Question 13

delta H degree sub rxn = (sum of delta H degree sub f of products) - (sum of delta H degree sub f of reactants)
One specific type of ___ of reaction is the standard heat of combustion, delta H degree sub comb

Answer 13

enthalpy

Question 14

___ states that enthalpies of reactions are additive; if a reaction is broken down into individual steps, the overall enthalpy of the reaction is the sum of enthalpies for each step

Answer 14

Hess’s Law

Question 15

___ is the energy required to break a specific chemical bond in one mole of gaseous molecules

Answer 15

bond dissociation energy

Question 16

Since it takes energy to pull two atoms apart, ___ breaking is always endothermic and bond formation is always exothermic

Answer 16

bon

Question 17

delta H sub rxn = (delta H of bonds broken) - (delta H of ___ formed) = total energy input - total energy released

Answer 17

bonds

Question 18

___ (S) is a measure of the disorder, or randomness, of a system

Answer 18

entropy

Question 19

For any substance, ___ (solid to gas) will be the phase transition with the greatest entropy change

Answer 19

sublimation

Question 20

A system reaches its maximum entropy at ___, a state in which no observable change takes place as time goes on
delta S sub universe = delta S sub system + delta S sub surroundings = 0

Answer 20

equilibrium

Question 21

A system will spontaneously tend toward an equilibrium ___ if left alone

Answer 21

state

Question 22

delta S degree sub rxn = (sum of S degree sub products) - (sum of S degree sub ___)

Answer 22

reactants

Question 23

The thermodynamic state function G, known as Gibbs free energy, provides information on how both enthalpy and entropy ___ affect a reaction

Answer 23

changes

Question 24

delta G = delta H - TdeltaS

where T is the absolute ___in kelvin

Answer 24

temperature

Question 25

In the equilibrium state, free ___ is at a minimum

Answer 25

energy

Question 26

1. If delta G is negative, the ___ is spontaneous and proceeds forward
2. If delta G is positive, the reaction is not spontaneous, and the reverse reaction occurs
3. If delta G is zero, the system is in a state of equilibrium; thus delta G = 0 and deltaH = TdeltaS

Answer 26

reaction

Question 27

The rate of a ___ depends on the activation energy, not on deltaG. Spontaneity indicates whether or not a reaction will occur but not the rate of the reaction

Answer 27

reaction

Question 28

Spontaneity indicates whether or not a reaction will occur but not the ___ of the reaction

Answer 28

rate

Question 29

Enthalpy and ___ may act together to drive a reaction forward or backward, or they may oppose each other

Answer 29

entropy

Question 30

The temperature will determine whether entropy or ___ has a greater effect on the spontaneity of a reaction, and the reaction is considered to be temperature-dependent

Answer 30

enthalpy