Chapter 6 (chemical reactivity and mechanisms)

Question 1

define enthalpy

Answer 1

the amount of energy exchanged between a molecule and its surroundings upon bond formation and bond breaking

Question 2

define homolytic bond cleavage

Answer 2

bond breaks and each species takes one electron from bond

Question 3

define heterolytic bond cleavage

Answer 3

bond breaks and one species takes both electrons from bond

Question 4

what is bond dissociation energy?

Answer 4

the energy required to homolytically break a covalent bond

Question 5

what does breaking a bond require?

Answer 5

an input of energy

Question 6

what does forming a bond do?

Answer 6

releases energy

Question 7

when calculating a heat of reaction, bonds that are broken should have a positive or negative sign for H?

Answer 7

positive

Question 8

when calculating heat of a reaction, bonds that are formed should have a positive or negative sign for H?

Answer 8

negative

Question 9

in an endothermic reaction, is delta H greater than or less than zero? what does this indicate?

Answer 9

delta H is greater than zero for an endothermic reaction; energy input from surroundings

Question 10

in an exotehrmic reaction, is delta H greater than or less than zero? what does this indicate?

Answer 10

delta H is less than zero for an exothermic reaction; energy given off to surroundings

Question 11

what 2 types of bonds make up a double bond?

Answer 11

a sigma bond and a pi bond

Question 12

is a spontaneous reaction is delta S (change in entropy) greater than or less than zero? what does this indicate?

Answer 12

delta S is greater than zero, increase in entropy

Question 13

define an exergonic reaction (delta G, what is favored)

Answer 13

delta G less than zero, reaction favors products

Question 14

define an endergonic reaction (delta G, what is favored)

Answer 14

delta G greater than zero, reaction favors reactants