Kinetics Unit

Question 1

What is kinetics?

Answer 1

The study of chemistry that examines the rates of chemical reactions and the mechanisms by which chemical reactions take place.

Question 2

What is collision theory?

Answer 2

The concept of kinetics that says in order for a reaction to take place reactant particles must collide.

Question 3

What is an effective collision?

Answer 3

a collision which results in a reaction

Question 4

what conditions must be present for an effective collision?

Answer 4

• particles must have enough kinetic energy
• the particles must collide at the proper angle.

Question 5

in exothermic reactions, does potential energy decrease or increase?

Answer 5

decrease

Question 6

in endothermic reactions, does potential energy decrease or increase?

Answer 6

increases

Question 7

what is activation energy

Answer 7

the amount of energy required to initiate a chemical reaction. it is added to the reactants and forms the activated complex

Question 8

what is heat of reaction

Answer 8

the amoutn of energy released in an exothermic reaction or absorbed in an endo thermic reaction

Question 9

what is delta H the difference of

Answer 9

the final potential energy - the initial potential energy

Question 10

if the reaction is exothermic, is the heat of reaction positive or negative

Answer 10

negative

Question 11

if the reaction is endothermic, is the heat of reaction positive or negative

Answer 11

positive

Question 12

what are reversible reactions

Answer 12

reactions where once the products form, they can react with each other, reforming the reactants.

Question 13

what are catalysts

Answer 13

increases the rate of a chemical reaction by lowering the activation energy required. catalysts do not change delta H for the forward or reverse reaction

Question 14

how does concentration affect rate of reaction

Answer 14

if the concentration is increased, the reaction rate will be increased. b/c the greater the concentration, the form effective collisions and the fewer water molecules that interfere with collisions.

Question 15

how does temperature affect rate of reaction

Answer 15

the higher the temperature, the greater the rate of reaction because the molecules of a substance will move faster causing more effective collisions.

Question 16

how does the nature of the reactants affect rate of reaction

Answer 16

ionic compound reactions are faster because the bonds are already broken and only new ones have to be formed. in covalent substances, the bonds have to be broken first.

Question 17

how does presence of a catalyst affect rate of reaction

Answer 17

it increases it by providing an easier pathway for the reaction. the catalyst remains unchanged after the reaction.

Question 18

how does surface area affect the rate of reaction

Answer 18

the smaller the particles, the greater the rate of reaction. more area is exposed for the substance to react with and there are more chances for the reactant particles to collide.

Question 19

how does pressure affect the rate of reaction

Answer 19

has little affect on non-gases. for gases, increased pressure will result increase rate of reaction by increasing the frequency of collisions.

Question 20

what is enthalpy

Answer 20

the total heat content of a system (at constant pressure) delta h is also called change in enthalpy

Question 21

at is standard heat of formation

Answer 21

delta Hf ^o
change in enthalpy when one mole of a compound is formed from its elements at one atmosphere and 298k

Question 22

where is the energy term put for exothermic reactions

Answer 22

with the products, endothermic is the opposite

Question 23

what is Hess’ law of heat Summation

Answer 23

if a chemical reaction can be expressed as the algebraic sum of two other equations, the heat of reaction for the final reaction will be the sum of the heats of reaction of the other 2 equations

Question 24

what are spontaneous reactions?

Answer 24

a reaction in which, once begun, with continue with no outside intervention, it favors the formation of products at the specified conditions of the reaction.

Question 25

what is enthalpy

Answer 25

the loss or gain of heat

Question 26

what do systems tend to go to

Answer 26

lower states of energy, or enthalpy

Question 27

are exothermic reactions or endothermic reactions more likely to be spontaneous

Answer 27

exothermic reactions are more likely to be spontaneous because there is more energy in the reactants than the products

Question 28

what is entropy

Answer 28

the measure of disorder or randomness of a system

Question 29

what is the tendency of nature in regards to entropy

Answer 29

nature tends to go to a state of lower energy and higher entropy

Question 30

do compounds or free elements have more entropy

Answer 30

free elements have greater entropy or disorder

Question 31

if a state moves in an endothermic reaction (solid to liquid) what happens to dela S

Answer 31

it is positive, entropy increases

Question 32

what does an increase in entropy favor

Answer 32

a spontaneous reaction

Question 33

what is gibs free energy equation

Answer 33

delta G = delta H - T delta S

Question 34

what is the gibs free energy equation used to determine

Answer 34

if a reaction is spontaneous

Question 35

what does delta g have to be in order for the reaction to be spontaneous

Answer 35

negative

Question 36

if delta H is negative and delta S is positive, what will delta G be

Answer 36

negative and will favor a spontaneous reaction

Question 37

if delta H is positive and delta S is negative, what will delta G be

Answer 37

positive, not spontaneous