Chemistry Unit 4 Test

CHEM 120

energy

ability to do work (E)

work

result of an object acting under applied force (w)

heat

flow of energy caused by differences in temperature (q)

system is always the

reaction

negative work

Work is applied in the direction opposite to the displacement of an object, resulting in a decrease in energy.

positive work

work is being done to it by an external force on a system, resulting in an increase in energy.

delta H negitive

exothermic. heat is released

delta H positive

endothermic. heat is absorbed

energy released by reaction is from

bonds

exothermic (-H) or endothermic (+H), thermodynamically favored?

exothermic, because the products from the reaction are lower in potential energy than the reactants. A lower potential energy is chemically favored. 

calculating delta H from bond energies

bonds broken + bonds formed

least entropy favored state

solid

most entropy favored state

gas

entropically unfavored

order and neatness, negitive

entropically favored

disorder and randomness, positive

H negative, S positive

G negitive, thermodynamically favored

H positive, S negitive

G positive and thermodynamically unfavored.

H positive, S positive

G depends, thermodynamically favored at high temperatures.

H negative, S negative

G depends, favored when temperature is low

chemical equilibrium

state in which the concentrations of reacttants and products in a reaction do not change with time

in equilibrium, concentrations don’t change, thsi process is generally…

dynamic, as reactants form products and products form reactants

k>1

since products is big and in the numerator. G is negitive, favored.

k<1

since reactants is big and in the denominator

conforminational analysis

study of bond rotations and the energy needed for bond rotation to occur

staggered

is lower in energy, more relaxed. favored

eclipsed

higher in energy, torsinal strain. unfavored

torsional strain

resistance to bond rotation cuased by repulsion between clouds. big bulky things getting in the way of each other. repulsion is source of energy.

what would happen to torsinal energy if you’ve got an atom larger than hydrogen attached to one or more carbons?

bigger group=more torsonail strainas repulsion increases between bulky groups.

which cycloalkane is more stable?

cyclohexaneis more stable than cyclopentane and cyclobutane due to its ability to adopt a chair conformation, minimizing torsional strain.

put bigger molecules in the

equatorial position to reduce torsional strain, making it more stable

cis

same side

trans

oppisite side