chem final-spontaneity

ΔS is _______________; a positive value helps _______________________

the change in entropy; make a reaction spontaneous

ΔG is ___________________; a negative value means ______________________

the change in free energy; a reaction will be spontaneous

If G=0, then the system is ________________

at equilibrium

If ΔH is positive (endothermic) and ΔS is positive, then will it always be spontaneous or non-spontaneous?

at low temperatures, the reaction will not be spontaneous, but it will be at high temperatures.

A nonspontaneous process moves a reaction system ____________________

away from equilibrium

Given that, at 25 degrees C, C(s) + O2(g) -->CO2 (g) (G=-394.4 kj) and C(s) + 1/2 O2(g) --> CO(g) (G=-137.2 kJ), Calculate delta G for the reaction below: CO (g) + 1/2 O2(g)-->CO2(g) a. -531.6 kJ b. -257.2 kJ c. -171.5 kJ d. +141.2 kJ e. +531.6 kJ

b. -257.2

The second law of thermodynamics states that a. in a spontaneous process, there is a net increase in entropy, taking into account both the system and the surroundings. b. there is no disorder in a perfect crystal at 0 K. c. the total energy of the universe is always increasing. d. the total energy of the universe is constant. e. mass and energy are conserved in all chemical reactions.

A

The third law of thermodynamics states that a. there is no disorder in a perfect crystal at 0 K. b. in a spontaneous process, the entropy of the universe increases. c. the total entropy of the universe is always increasing. d. the total mass of the universe is constant. e. mass and energy are conserved in all chemical reactions.

A

Given that S(g) + O2(g)-->SO2(g) (G=-300.1 kj) and 2S(g) + 3O2(g) -->2SO3(g) (G=-742.1 kj) calculate G formation of the following reaction: SO2(g) + 1/2 O2(g)-->SO3(g) a. -1042.2kj b. -71.0 kJ c. +2.47 kJ d. +71.0 kJ e. +1042.2 kJ

B. -71.0 kJ

All of the following are true except: a. delta S>0 for systems that become more disorderly. b. reactions are spontaneous when delta G<0 c. reactions are spontaneous when delta H<0 d. delta H <0 for exothermic reactions e. generally, nature tends to move from more ordered to more random states

C

Which of the following statements concerning entropy is/are CORRECT? 1. The entropy of a substance increases when converted from a liquid to a solid. 2. The entropy of a substance decreases as its temperature increases. 3. All substances have positive standard molar entropies at temperatures above 0 K. a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

C

If a chemical reaction has a negative change in entropy, ΔS, then a. the reaction is endothermic. b. the reaction is spontaneous. c. the equilibrium constant is greater than 1. d. there is an increase in the order of the system. e. the change in Gibbs free energy, ΔG, is negative.

D

The following processes occur spontaneously at 25°C. Which of these processes is/are endothermic? 1. NH4NO3 dissolving in water (which is accompanied by a cooling of the water). 2. the expansion of a real gas into a vacuum (which is accompanied by a cooling of the gas). 3. liquid water in an ice cube tray freezing into ice after being placed in a freezer. a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

D- 1 and 2

All of the following events result in an increase in entropy EXCEPT a. the melting of candle wax. b. the combustion of carbon. c. the dissolution of sodium chloride in water. d. the evaporation of ethanol. e. the formation of N2O4(g) from NO2(g).

E

Which of the following linear chain alcohols is likely to have the largest standard molar entropy in the liquid state? a. CH3OH b. CH3CH2OH c. CH3CH2CH2OH d. CH3CH2CH2CH2OH e. CH3CH2CH2CH2CH2OH

E) because it has the most atoms which has the most potential to create disorder.

Entropy is given the symbol ____

S

Which of the following are conditions for the standard gibbs free energy? a. ions or molecules in solution are present at one molar concentration b. gases are present at one atmosphere partial pressure c. the temperature of the system is 273 K

a and b

For the decomposition of calcium carbonate, delta G = +130.4 kJ at 25 degrees C. CaCO3 (s) --> CaO (s) + CO2 (g). Calculate the partial pressure of CO2 if delta G = 0.0 kJ. a. 1.3X10^-23 atm b. 2.7 X 10^2 atm c. 8.2 x 10^-5 atm d. 5.3 x 10^1 atm e. 7.4 x 10^22 atm

a. 1.3 x 10^-23

At 298 K, all of the following substances have a standard free energy of formation of zero except: a. Br2(g) b. I2 (s) c. S8(s) d. Cl2(g) e. Hg(l)

a. Br2

when things dissolve, there is ______________ in entropy

an increase

Entropy is often described as __________________

an increase in disorder or randomness

Which phase changes are exothermic?

condensation and freezing (molecules move closer together)

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ at 298K. NH4NO3 (s) <--> NH4NO3 (aq). what is the equilibrium constant for the reaction? a. 1.9 x 10^-3 b. 6.6 x 10^-2 c. 1.0 d. 15 e. 5.2 x 10^2

d. 15

In a gas phase reaction, what is the effect of increasing reactant or product pressure on the standard Gibbs free energy, delta G?

delta G is unchanged

Equation for a spontaneous process:

delta S(universe)=(delta S (system) + delta S (surroundings) ) >0

All of the following events result in an increase in entropy except: a. the melting of candle wax b. the combustion of carbon c. the dissolution of sodium chloride in water d. the evaporation of ethanol. e. the formation of N2O4(g) from NO2 (g)

e

J. Willard Gibbs, professor at Yale from 1871 to 1903, a. was a reasearcher, experimenting with high energy reactions b. was a theoretician who studied chemical thermodynamics c. received no salary for the first ten years d. both a and c e. both b and c

e. (both b and c)

For the dimerization of nitrogen dioxide, delta G= -4.7 kJ at 25 degrees C. 2NO2(g)-->N2O4 (g) Calculate delta G for this reaction if the partial pressures of NO2 and N2O4 are both 0.50 atm. a. -6.4 kJ b. -4.8 kJ c. -4.7 kJ d. -4.6 kJ e. -3.0 kJ

e. -3.0 kJ

bond breaking is ___________________

endothermic

Note that standard molar entropies are usually smaller in magnitude than _______________

enthalpies

Gas-forming reactions always have positive ____________________

entropy changes

bond forming is

exothermic

True or false? the entropy for gaseous elements is zero at 298 K

false. even gaseous elements have non zero entropy at 298 K

A gas has (lower/higher) entropy than the liquid or solid from which it formed

higher

A liquid has ______________ entropy than the solid from which it formed

higher

Randomness is of ______________ probability than order

higher

nature favors ______________ in entropy and _______________ reactions

increase, exothermic

Increasing the temperature of a substance ___________ entropy

increases

disorder ______________ with mixing

increases

as the amount of gas increases, randomness _________________, so entropy _______________

increases; increases

Rubber elasticity is an entropic phneomenon. As a rubber band is stretched the entropy of the system _______________

is reduced

Nature tends to move spontaneously from a state of ___________________ to one of __________________

lower probability (order); higher probability (disorder)

Each system which is left to its own, will, over time, change toward a condition of __________________

maximum probability

which phase changes are endothermic?

melting, evaporating, sublimating, boiling (molecules move further apart

Gases are (less/more) random than either liquids or solids

more

Liquids are (more/less) random than solids

more

If a reaction is spontaneous in one direction, it will be _________________ in the reverse direction under the same conditions

non-spontaneous

If ΔH is positive and ΔS is negative, the reaction is ___________________

not spontaneous at any temperature.

Nature tends to move from more ___________ to more __________ states

ordered; random

Standard molar entropies are always , i.e., S° _____________

positive numbers; > 0

For a chemical reaction, delta G and delta Gnaught are equal when:

products and reactants are in standard state concentrations

Molecular kinetic energy increases, and with it, __________________

randomness

If ΔH is negative (i.e. exothermic) and ΔS is positive (i.e. entropy increases), then the reaction will be _______________

spontaneous at any temperature.

When an apparatus consisting of flasks of hydrogen and nitrogen is opened to allow the gases to mix, the process proceeds with the result being a random mix of both molecules This process is _______________ The system _______________ spontaneously separate itself into hydrogen and nitrogen The mixture is (less/more) random than the pure gases

spontaneous; will not; more

If a chemical reaction has a negative change in entropy (delta S), then _____________________

there is an increase in the order of the system

A spontaneous process moves a reaction system __________________

toward equilibrium

A completely ordered, pure crystalline solid at 0 K has an entropy of _____________

zero. This is the only time the entropy of a substance is zero