Chapter 9 - Chemical Kinetics

Is kinetics and thermodynamics synonymous?

No, they differ in the information they provide in regards to a chemical reaction

What information does thermodynamics provide with?

Provides info on the spontaneity of a chemical reaction

What information does kinetics provide with?

The rate at which a reaction takes place

Does the spontaneity of a reaction have bearing on the speed of the reaction?

No

Is it possible for a spontaneous reaction to occur at a fast rate?

Yes

Is it possible for a spontaneous reaction to occur at a slow rate?

Yes. Spontaneity has no bearing over the speed of the reaction

What exists on the top of the bump on a reaction coordinate diagram?

The transition state

What is occurring during the transition state?

Old bonds are breaking and new bonds are forming

Why is an elementary reaction also called a 'single step reaction'?

Because it only has one transition state

If products are lower in energy than the reactants on a reaction coordinate diagram, is the reaction exothermic or endothermic?

Exothermic

If products are lower in energy than the reactants on a reaction coordinate diagram, what does this suggest about the change in enthalpy?

Change in enthalpy is negative

What does activation energy refer to?

The minimum amount of energy the reactants must possess in order for the reaction to occur

Is activation energy the same as change in enthalpy?

No

How does activation energy differ from enthalpy?

Activation energy is the energy needed to overcome over the hump. Enthalpy is the difference between the energies of the reactants and products

What agent can be added to lower activation energy?

A catalyst

Why do catalysts not appear as reagents in the chemical equation?

Because they are not consumed by the reaction

What are intermediates?

Species that are formed during the course of the reaction and are hence termed "intermediates"; they are not part of the reactants nor the products

Can intermediates be isolated from the mixture?

Yes it is possible

Can transition states be isolated from the mixture?

No

Do intermediates have higher or lower energy levels than that of transition states?

Lower

What is a rate law an expression of?

A mathetmatical expression that specifies the relationship between the reaction rate and reactant concentrations

What letter is used to express rate constant?

Lower letter 'k'

What letter is used to express equilibrium constant?

Upper letter 'K'

Which order is least common: zero, first, or second order?

Zero order

In a zero order reaction, does concentration of reactants affect the rate constant?

No

In a first order reaction, does concentration of reactants affect the rate constant?

No

If you were to double the reactant concentration in a first order reaction, what happens to the rate constant?

Rate would double. In a first order reaction, rate of reaction is proportional to changes in reactant concentration

Can the orders in the rate law for a reaction be determined by looking at the coefficients in the chemical reaction?

No. You cannot depend on reaction coefficients to determine rate order

Which order reaction graph plot is the only one to have a positive slope?

Second order

What is the y-axis unit for zero order reaction?

[A]

What is the y-axis unit for first order reaction?

ln [A]

What is the y-axis unit for second order reaction?

1 / [A]

What is the rate constant units for a zero order reaction?

M/s

What is the rate constant units for a first order reaction?

1/s

What is the rate constant units for a second order reaction?

1/(M・s)

The reaction that determines the rate of the overall reaction is known as?

The rate determining step (RDS)

Is RDS the slowest or fastest step in a chemical reaction?

The slowest

If an agent is consumed as a reactant in one step but then regenerated as a product in another step, is it considered a catalyst?

Yes, it can be

What are the three conditions that must be met in collision theory?

1. Molecules must collide

2. Molecules must have the proper orientation (when they collide)

3. Molecules must have sufficient energy to overcome the Ea barrier

Based off the Arrhenius equation, are reaction rates dependent on temperature?

Yes. As you increase temperature, the negative exponent power shirnks, leading to a larger k value

What happens to rate constant (k) after adding a catalyst?

Activation energy will decreasing, leading to a larger rate constant

Does increasing the concentration of reactants affect rate constant?

No. Reactant concentration does not appear as a variable in the Arrhenius equation

Does increasing concentration of reactants affect reaction rate?

Yes

What does half-life refer to?

The time it takes to convert half of the reactant to product.

Is the half-life for a zero order reaction dependent on reactant concentration?

Yes

How does half-life for a zero order reaction change as reactant concentration decreases?

Half-life also decreases

Is the half-life for a second order reaction dependent on reactant concentration?

Yes

How does half-life for a second order reaction change as reactant concentration decreases?

Half-life increases as reactant concentration decreases

Is the half-life for a first order reaction dependent on reactant concentration?

No. It is the only order reaction that is independent of reactant concentration.

If a compound has a half-life of 3 hrs, how many half-lives have passed after 9 hours?

3 half-lives

The decomposition of compound Z follows first order kinetics. If the initial weight is 100g and it has a half-life of 5 minutes, how much of compound Z remains after 10 minutes?

25g

The decomposition of compound Z follows first order kinetics. If the initial concentration is 100g and it has a half-life of 5 minutes, how much of compound Z has decayed after 15 minutes?

87.5g