Solutions +Kinetics Test

Question 1

What is kinetics?

Answer 1

The study of reaction rates

Question 2

What is collision theory?

Answer 2

For a reaction to occur, reactant molecules have to collide

Question 3

What does a good collision have to have?

Answer 3

• Enough energy to overcome activation energy
• The molecules have to hit each other with correct orientation

Question 4

What happens if you increase the number of effective collisions?

Answer 4

The reaction rate will increase

Question 5

What are the factors that affect rate (or # of effective collisions)?

Answer 5

• States of matter (solid, liquid, gas, aqueous) (Gas and aqueous molecules have greater surface area)
• Surface area (greater surface area means greater number of effective collisions meaning faster rate)
• Concentration (greater concentration means more effective collisions meaning faster rate)
• Temperature (greater temp. means greater speed of molecules meaning more effective collisions meaning faster rate)
• Catalysts (lower activation energy meaning more effective collisions and a faster rate)

Question 6

How do you measure rate?

Answer 6

• By looking at changes in reactant OR product amounts over time

Ex. 2A + 1B -> 3C
A is disappearing twice as fast as B because, for every 1 molecule of B that’s used up, 2 molecules of A are used up

*Most reactions slow down over time (except 0 order reactions with constant rates)

Question 7

How to measure instantaneous rate?

Answer 7

Take the slope of a tangent line at a certain point in time

Question 8

What are reaction orders?

Answer 8

• Tells you how much the concentration affects the rate
• 0 order is when the concentration does not affect the rate at all
• 1st order is when the concentration affects the rate a little bit
• 2nd order is when the concentration affects the rate a lot

Question 9

What is a rate law?

Answer 9

Expresses or quantifies how much concentration affects rate

Rate = k[ ]^x

• Reactants go inside concentration brackets
  -Thereaction order (exponent x) is determined by conducting an experiment
• Find the overall reaction orders by adding up all the exponents in the rate law

Question 10

What are the two types of experiments used for rate laws?

Answer 10

• Multiple different experiments with different initial concentrations and looking at how rate was affected
• Running one experiment to completion and watch how concentration and rate change over time

Question 11

If a concentration over time graph is linear, meaning the reaction does not slow down over time, what reaction order is it?

Answer 11

Zero order because the reduction of concentration over time did not affect the rate

Question 12

If a concentration over time graph depicts a downward curve, meaning the reaction is slowing down over time, what reaction orders is it?

Answer 12

1st or 2nd order because the reaction is slowing down over time

Question 13

What reaction order is depicting if the natural log of concentration versus time is graphed and its linear?

Answer 13

1st order

Question 14

What reaction order is depicted if 1 over the concentration versus time is graphed and it is linear?

Answer 14

2nd order

Question 15

What is the differential rate law for a zero order reaction?

Answer 15

Rate = k

Question 16

What is the differential rate law for a first order reaction?

Answer 16

Rate = k[A]^1

Question 17

What is the differential rate law for a second order reaction?

Answer 17

Rate = k[A]^2

Question 18

What is the integrated rate law for a zero order reaction?

Answer 18

[A]t = -kt x [A]i
y = mx + b

(-k = slope of zero order graph line)

Question 19

What is the integrated rate law for a first order reaction?

Answer 19

ln[A]t = -kt + ln[A]i

(-k = slope of first order graph line)

Question 20

What is the integrated rate law for a second order reaction?

Answer 20

1/[A]t = kt + 1/[A]t

(k = slope of second order graph line)

Question 21

What is the half life for first order reactions?

Answer 21

Constant

Question 22

What is the Arrhenius Equation?

Answer 22

k = A x e^-Ea/RT

A = frequency factor (a measure of how many collisions have the correct orientation)
e^Ea/RT = indicates how many collisions have enough energy that is greater than the activation energy
R = 8.314 J/molK

Integrated = lmk = -Ea/RT + lnA
y = mx + b

Question 23

A reaction will only happen as fast as….?

Answer 23

It’s slowest step (rate limiting step) (tallest hump of a PE graph)

Question 24

What is an intermediate?

Answer 24

A part of the reaction that is produced and consumed so it looks like it was never a part of a reaction at all

A + B -> C
C + D -> E
Overall: A + B + D -> E
The intermediate is C

Question 25

What is solubility?

Answer 25

Measured amount of solute that can dissolve in a given amount of solvent at a particular temperature and pressure

Question 26

What happens to solubility when temp. increases?

Answer 26

Solids and liquids become more soluble and gasses become less soluble

Question 27

The solubility of a gas is….

Answer 27

Directly proportional to the vapor pressure of the gas above the solution

Question 28

What does it mean when a solution is saturated?

Answer 28

The max amount of solution is dissolved

Question 29

What does it mean when a solution is unsaturated?

Answer 29

Less than the max amount of solution is dissolved

Question 30

What does it mean when a solution is supersaturated?

Answer 30

More than the max amount of solution is dissolved. Happens when a solution is heated.

Question 31

What are colligative properties?

Answer 31

Properties of a solvent that change depending upon how much solute is dissolved (independent of solute identity)

Question 32

Vapor pressure lowering

Answer 32

Solvents have less vapor pressure when solutes are dissolved to become solutions

Question 33

What is entropy?

Answer 33

Entropy is disorder. Increasing entropy is favorable.