[CHEM] Unit 11- Kinetics

Question 1

In order to react, reactants need to have:

Answer 1

Effective collisions

Question 2

Two things are needed for effective collisions:

Answer 2

1) Enough energy

2) Proper orientation (based on polarity)

Question 3

To react quickly, ionic reactants need to be in the ___ phase

Answer 3

Aqueous (aq)- solid ionic reactants don’t break apart

Question 4

Covalent reactants typically have ___ bonds to break and so react ___

Answer 4

More, slowly

Question 5

Temperature is a measure of the:

Answer 5

Average kinetic energy of the particles

Question 6

A high temp leads to ___ energy, and so ___ particles will collide with sufficient energy

Answer 6

Higher, more

Question 7

A high temp also leads to:

Answer 7

Particles moving faster, and so more total collisions will occur

Question 8

How does concentration affect rate?

Answer 8

Higher concentration=faster rates because there are more total collisions

Question 9

Pressure only affects ___ reactants

Answer 9

Gas

Question 10

How does pressure affect rate?

Answer 10

Pressure is caused by the particles colliding with the walls of the container- more collisions will walls will mean more collisions between particles

Question 11

How does surface area affect rate?

Answer 11

Reactions only occur at the surface where the reactants are in contact; therefore, as surface area increases, there will be more total collisions (and in turn more effective collisions)

Trick to remember: Sugar cubes vs powdered sugar

Question 12

How does one increase surface area?

Answer 12

For solids, grind them into small pieces

For liquids, stir

Question 13

How does a catalyst affect rate?

Answer 13

Catalysts reduce the required energy for an effective collision, thereby making more (already existing) collisions effective

Question 14

T/F: A catalyst is used up during a reaction

Answer 14

F

Question 15

Endothermic=

Answer 15

Heat put in (heat is a reactant)

Question 16

Breaking/forming a bond is endothermic

Answer 16

Breaking!

Question 17

Exothermic=

Answer 17

Heat is released (heat is a product)

Question 18

Breaking/forming a bond is exothermic

Answer 18

Forming!

Question 19

On a PED, if a reaction is endothermic, the ΔH is:

Answer 19

Positive

Question 20

On a PED, if a reaction is exothermic, the ΔH is:

Answer 20

Negative

Question 21

ΔH is:

Answer 21

Heat of reaction, or change of enthalpy

Question 22

How does one tell if a PED is exothermic or endothermic?

Answer 22

Products have more energy= Endothermic

Products have less energy= Exothermic

Question 23

The activated complex is:

Answer 23

The peak of potential energy; a state between reactants and products

Question 24

Activation energy is:

Answer 24

The difference between the PE of the activated complex and the PE of the reactants

Question 25

ΔH is calculated by:

Answer 25

PE of products - PE of reactants

Question 26

If a catalyst is added to a PED, what changes?

Answer 26

The activation energy is reduced, and the PE of the activated complex is also reduced. *ΔH DOES NOT CHANGE*

Question 27

In a reverse PED, the products become the ____ and the reactants become the ___

Answer 27

Reactants, products

Question 28

To find the activation energy of a reverse PED, one needs to

Answer 28

FInd the different between the PE of the products and PE of the activated complex

Question 29

T/F: In a reverse reaction/PED, the ΔH changes

Answer 29

T

Question 30

T/F: The reverse reaction is always the opposite of the normal reaction (in terms of endothermic vs exothermic)

Answer 30

T

Question 31

When using Table I for changes in enthalpy, if the coefficients of the reactants/products are changed, then:

Answer 31

The ΔH must be changed accordingly (doubled, halved, etc)

Question 32

In terms of enthalpy (ΔH), nature tends to favor ___ energy- ie ___thermic

Answer 32

Low, exo

Question 33

Entropy is:

Answer 33

Randomness or disorder

Question 34

In terms of entropy (ΔS), nature tends to favor ___ entropy

Answer 34

Higher

Question 35

The phase lowest in entropy is:

Answer 35

Solid

Question 36

The phase(s) highest in entropy is/are:

Answer 36

Gas and aq

Question 37

The phase in the middle in terms of entropy is:

Answer 37

Liquid

Question 38

One way to increase entropy is to:

Answer 38

Mix the subtances

Question 39

Higher temperature=___ ΔH

Answer 39

Higher

Question 40

The equation for Gibbs Free Energy is:

Answer 40

ΔG= ΔH- T(ΔS) ***TEMPERATURE HAS TO BE KELVIN!!***

Question 41

For a reaction to be spontaneous, the ΔG has to be:

Answer 41

Negative

Question 42

A positive ΔH (___) and negative ΔS means:

Answer 42

Endo; the reaction is ALWAYS positive- therefore it is never spontaneous

Question 43

A negative ΔH (___) and positive ΔS means:

Answer 43

Exo; the reaction is ALWAYS negative- therefore it is always spontaneous

Question 44

Both a negative ΔH and ΔS means:

Answer 44

The reaction is only spontaneous at LOW temperatures

Question 45

Both a positive ΔH and ΔS means:

Answer 45

The reaction is only spontaneous at HIGH temperatures