Chemical Kinetics

Question 1

which factor does not affect homogenous reactions

Answer 1

Surface Area

Question 2

Catalysts

Answer 2

• provide alternate pathway for reaction requiring less energy to occur
• lowers activation energy - increase probabality of successful collisions

Question 3

Pressure

Answer 3

affects volume of reaction and therefore changes concentration of reactant species (only applies to gases)

Question 4

nature of reactants

Answer 4

rate of chemical reaction based on strength of bonds, number of reactant species, number of bonds to be broken

Question 5

Concentration

Answer 5

• increase in concentration increases number of collisions and the probability of effective collisions
• does not affect solids - their concentrations are based on density and fixed

Question 6

which factors do not affect solids

Answer 6

concentration, pressure

Question 7

rates based on phase/state

Answer 7

Solids - slow rate due to inability to move

Gases - fast rate due to speed of reactants

Liquids - fast due to proximity of reactants

Aqueous - fastest due to proximity, movement via solution and ionic attraction (ions from ionic solutions already dissociated and free to react)

Question 8

conversion of energy

Answer 8

• as reactant particles approach and electron clouds begin to interact, K.E. is converted to P.E. (particles slow down)
• once in contact all K.E. is now P.E. (reactants come to stand still)
• if sufficient energy - ac forms
• insufficient energy - all energy is converted back to ke

Question 9

exothermic

Answer 9

• -delta H due to energy released to surroundings
• energy is released when bonds form between products
• surroundings become warmer, system cooler

Question 10

endothermic

Answer 10

• +delta H due to energy absorbed by system
• energy is required to break bonds between reactants
• system absorbs energy from surroundings
• surroundings become cooler, system becomes warmer

Question 11

activated complex

Answer 11

a molecular conglomerate that allows for bond breakage, electron movement, bond forming, and resulting new molecules (products)

Question 12

what would the rate at which products are produced graph look like?

Answer 12

graph is decreasing as reactant concentration is decreasing (rate reactants are used = rate products are produced)

Question 13

rule of thumb for doubling rates

Answer 13

SLOW reaction rates double by each 10* increase

Question 14

what factors affect ke distribution graphs

Answer 14

• factors that influence kinetic energy (temperature)
• factors that influence # molecules (concentration, reactant used up)

Question 15

how do the number of electrons impact activation energy

Answer 15

more electrons = more repulsion, overcoming repulsion requires more energy

Question 16

kinetic energy of endothermic vs exothermic products

Answer 16

(graph shows potential energy)
- endothermic products have greater potential energy than exothermic, thus their kinetic energy is smaller

Question 17

overall rate of a reaction

Answer 17

rate determining step