Kinetics Lesson 4-6 MIDTERMS

• Parallel Reactions

• Series Reactions

• Independent Reactions

Three Basic Types of Multiple Reactions

Competing reactions

Parallel reactions are also called _____________

Parallel reactions

The reactant is consumed by two different reaction pathways to form different products

desired and undesired

In Parallel reactions, the reactant is consumed by two different reaction pathways to form different products: _________ and _________

To maximize formation of the desired product

The goal of engineers in parallel reactions

Consecutive Reactions

Series reactions are also called?

Series Reactions

The reactant forms an intermediate product, which reacts further to form another product.

Independent Reactions

Reactions occurring simultaneously but independent from each other. Occur in feed stocks containing many reactants.

Cracking of crude oil to form gasoline

Example of Independent Reactions

Autocatalytic Reactions

A reaction in which one of the products of reaction acts as a catalyst.

A catalyst

-substance that affects the rate of reaction but emerges from process uncharged.

molecular path (mechanism)

A catalyst usually changes a reaction rate by promoting a different __________________ for the reaction.

FALSE
A catalyst can accelerate the reaction rate but cannot change the equilibrium.

TRUE or FALSE
A catalyst can accelerate the reaction rate but CAN change the equilibrium.

• Gaseous reactants

• Gas-phase reaction

• Volume changes with time

Properties of a reaction in a constant pressure batch reactor

The volume of the reacting system varies linearly with conversion

What is the assumption in Autocatalytic Reactions?

Half-life

time it takes to convert for half of the initial concentration.

Space time,

time required to process one reactor volume of feed measured at specified condition.

Fao

time required to process one reactor volume. It is the time it takes for the amount of fluid that takes up the entire volume of the reactor to either completely enter or completely exit the reactor.

Fao

also used as capacity measurement for chemical reactors.

Space Velocity, s

the volume of entering feed at specified conditions per unit time per void volume of reactor.

Holding Time

- retention time of reactants inside the reactor volume.

1/t

The unit of k for a first order elementary reaction is

Directly proportional

Relationship of K to how far the reaction is to completion

2

If the temperature of a chemical reaction is raised by I0°C, the rate of reaction is increased by a factor of about

Adding a catalyst

The activation energy, E of a reaction may be lowered by

Rate equation

The mechanism of a reaction can sometimes be deduced from

Mass action

The law governing the kinetics of a reaction is the law of

does not depend on the initial concentration

The equilibrium constant in a reversible chemical reaction at a given temperature

Rate of reaction

It increases the number of particles with the necessary activation energy

Zero order

If the rate of reaction is independent of the concentration of the reactants, the reaction is said to be

Temperature

The specific rate of reaction is primarily dependent on.

molecularity of the reaction

The rate of reaction is not influenced by

Non-elementary

For the reaction 2A(g) + 3B(gl ~ D(g) + 2E(g) with r0 = kCAC8 2 the rea~tion is said to be

Pressure

Chemical reaction rates in solution do not depend to any extent upon

3

The overall order of reaction for the elementary reaction A+ 2B = Cis

2ra

The rate of formation of B in terms ofrA (where rA = -kCACb&2 )

is

0

The net rate of reaction of an intermediate is

c. The rate of disappearance of C is one half the rate of consumption of A.

For the reaction: 4A + B = 2C + 2D

Which of the following statements is not correct?

a. The rate of disappearance· of B is one fourth the rate of disappearance of A.

b. The rate of appearance of C is one half the rate of disappearance of A.

c. The rate of disappearance of C is one half the rate of consumption of A.

d. The rate of formation of C and D are equal.

d. Rate is directly proportional to the number of collisions per second.

The collision theory of chemical reactions maintains that

a. A chemical reaction occurs with every molecular collision.

b. Reactions in the gas phase are always first order.

c. Reaction rates are of the order of molecular speeds.

d. Rate is directly proportional to the number of collisions per second.

log Ca vs time

A reaction is known to be first order in A. A straight line will be obtained by plotting

1/Ca vs. time

if the reaction, 2A --+ B + C is second order, which of the following plots will give a straight line?

log k vs 1/T

The activation energy of a reaction can be obtained from the slope of a plot of

-ra = CaCb²

For the reaction A + B —> 2C, when CA is doubled, the rate doubles. When Ca is doubled, the rate increases four fold. The rate law is

b. diminish the activation energy

A catalyst can

a. shift the equilibrium of reaction

b. diminish the activation energy

c. increase the rate constant of forward reaction

d. decrease the pressure

Law of Mass Action

It states that the rate of a chemical reaction is proportional to the activity of the reactants.

rapid increase in kinetic energy of molecules

Rapid increase in the rate of chemical reaction even for small temperature increase is due to

inversely proportional to initial concentration

The half-life of a material undergoing second order decay is

plug-flow reactor

The composition of the reaction component varies from position to position along a flow path in a/an

a. 7.5 x 10-4

A certain reaction is second order in A. When Ca is 0.03 mol/L, the rate is 3 x 10·3 L/mol-s. The rate when CA is 0.015 mol/L in L/mol-s is

a. 7.5 x 10-4

b. 1.5 X 10-3

c. 0.21

d. 3.33

231s

A certain reaction is first order in A. The specific rate constant is 3 x 10-3 /s. The half life is