Chapter 7

Question 1

Collision Theory Statements

Answer 1

Molecular collisions - reactant particles must collide
Activation energy - particles must posses enough activation energy
Collision Orientation - particles must come together in proper orientation

Question 2

Delta H = Energy of reaction =

Answer 2

Hproducts - Hreactants

Question 3

What if Hproducts - Hreactants is positive?

Answer 3

the energy of the products is higher than the energy of the reactants, so the reaction is endothermic

Question 4

What if Hproducts - Hreactants is negative?

Answer 4

the products are lower in energy than reactants, so the reaction is exothermic

Question 5

the step that requires the most activation energy determines ___

Answer 5

the rate of the reaction

Question 6

factors that influence chemical reaction rates

Answer 6

physical nature of reactants,
reactant concentrations,
reaction temperatures,
presence of catalyst

Question 7

Chemical kinetics rate equation

Answer 7

see image

Question 8

Rate Law Equation

Answer 8

see image
R=k[A]^x • [B]^y
***the orders (exponents) must be determined experimentally
k is the rate constant, and is specific to each reaction

Question 9

Keq expression for aA + bB < —> cC + dD

Answer 9

see image

Question 10

What states of matter aren’t included in the equilibrium constant expression?

Answer 10

solids and liquids

Question 11

factor that influences chemical equilibrium

Answer 11

only temperature

Question 12

What if the value of Keq is large, as in 10^10

Answer 12

more products than reactants;

equilibrium is to the right

Question 13

What if the value of Keq is between 10^3 and 10^-3

Answer 13

significant amounts of both reactants and products;

equilibrium is neither to the right nor the left

Question 14

What if the value of Keq is small, as in 10^-10

Answer 14

more reactants than products;

equilibrium is to the left

Question 15

There is no relationship between ___ and the value of Keq

Answer 15

reaction rate, because that depends on the activation energy of the forward and reverse reactions;
that determines how fast equilibrium is reached but not its position

Question 16

Le Chatelier’s Principle

Answer 16

If stress is applied to a system in equilibrium, the system will readjust in the direction that best reduces the stress

Question 17

Le Chatelier’s Principle re: temp changes

Answer 17

think of heat as a reactant if the reaction is endothermic
heat + reactants products
think of heat as a product if the reaction is exothermic
reactants heat + products

Question 18

Le Chatelier’s Principle re: pressure changes

Answer 18

think of increasing pressure as increasing moles of gaseous reactant or product
look at the total number of moles of each gas (stoich)
shift eq in the direction that has less moles to relieve the pressure

Question 19

if pressure is decreased, shift in the direction of ___ moles of gas to increase the pressure

Answer 19

if pressure is decreased, shift in the direction of MORE moles of gas to increase the pressure

Question 20

if pressure is increased, shift in the direction of ___ moles of gas to increase the pressure

Answer 20

if pressure is increased, shift in the direction of LESS moles of gas to increase the pressure

Question 21

Le Chatelier’s Principle re: concentration changes

Answer 21

If concentration of reactant/product is increased, shift to the opposite side to use up some of it
If concentration of a reactant/product is decreased, shift to the same side to make more of it