Chemical Kinetics Test

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Chemical Kinetics Test - 31

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Weekly Quiz Competition

Question 1
1 / -0

Which reaction in the diagram has the lowest activation energy?

A
$$A$$

B
$$B$$

C
$$C$$

D
$$D$$

E
All reactions have equal activation energy

Solution

In the given curves, activation energy will be lowest for the curve in which the peak is lowest of all as the initial energy of reactants is same for all curves.
$$\Rightarrow \quad $$ $$D$$ has the lowest activation energy.
Question 2
1 / -0

How would the activation energy of the reaction diagram above be affected by an increase in temperature?

A
The activation energy curve would grow taller.

B
The activation energy curve would grow shorter.

C
The activation energy curve would become inverted.

D
The activation energy curve would not be affected by an increase in temperature.

Solution

The increase in temperature increase the number of collision, which increases the rate of reaction. the activation energy curve would grow taller as the molecular collision occur at a higher temperature.
Question 3
1 / -0

Two molecules collide and a reaction not occur. Which of the following is not a valid explanation for this?

A
The molecules were not in the proper states of matter.

B
The molecules did not have enough kinetic energy.

C
The molecules were not oriented correctly when they struck each other.

D
The temperature of the reaction mixture was not high enough.

Solution

For a reaction to occur,

$$(i)$$ The two molecules must collide with proper orientation.

$$(ii)$$ They should have high kinetic energy.

$$(iii)$$ The temperature should be high.

$$(iv)$$ But the state of matter does not have any effect on the reaction.
The states of matter molecules do not affect the rate of reaction.
Question 4
1 / -0

Activation energy, by definition, is the minimum amount of energy required for reactants to form products. Which of the following is not true of activation energy?

A
The value of activation energy varies from reaction to reaction.

B
If molecules are moving fast enough, the collisions will result in kinetic energy that can be used to bend, stretch, and eventually break the bonds of the reactants releasing the potential energy in a usable form.

C
All reactions eventually form an intermediate that lowers the overall energy requirements of the reaction resulting in a relatively reasonable activation energy.

D
Reactants only form products if the activation energy barrier has been exceeded with usable kinetic energy from the system and /or surroundings.

Solution

The rate of the reaction increases when the temperature increases because the kinetic energy of molecules increases with increasing temperature. As a result, more molecular collisions occur with energy equal to or greater than the activation energy.
The value of activation energy varies from reaction to reaction.
Question 5
1 / -0

A graph of concentration versus time data for a first-order reaction gives a straight line in which of the following plots of the data?

A
$$[A]_{t} = -kt + [A]_{0}$$

B
$$ln [A]_{t} = -kt + ln [A]_{0}$$

C
$$\dfrac {1}{[A]_{t}} = kt + \dfrac {1}{[A]_{0}}$$

D
All of the above

E
None of the above

Solution

For the first order reaction,
$$ \ln { \cfrac { [{ A }_{ o }] }{ [{ A }_{ t }] } } =kt\\ \therefore \ln { [{ A }_{ o }] } =kt+\ln { { [A] }_{ t } } \\ \therefore \ln { [{ A }]_{ t } } =-kt+\ln { { [A }]_{ o } } $$
Question 6
1 / -0

Assertion: The rate of the reaction of iron and hydorchloric acid will increase if the iron pieces are cut into smaller pieces.
Reason: Increasing surface area of a reactant helps to reduce activation energy.

A
Both Assertion and Reason are true and Reason is the correct explanation of Assertion

B
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

C
Assertion is true but Reason is false

D
Assertion is false but Reason is true

E
Both Assertion and Reason are false

Solution

It is known that increasing the surface area of the reactants results in more collision of the reactants molecules in any given time which increases the rate of reaction. Due to an increase in surface area of reactant, the activation energy is reduced & the rate of reaction increases.
So, assertion & reason are true & reason is the correct explanation of assertion.
Question 7
1 / -0

In a reaction mechanism consisting of elementary reaction steps where the relative rate of each is given, which of the following is most likely to be the rate-determining step?

A
A step labeled fast

B
A step labeled moderate

C
A step labeled slow

D
It is not possible to tell which step is rate determining from this information.

Solution

In a multi-step reaction, the elementary step having the slowest-rate is always the rate determining step of the overall reaction.

Therefore, a step labeled slow will be the rate determining step.
Question 8
1 / -0

Here is another look at the reaction of crystal violet with sodium hydroxide, a first-order reaction (ln $$A$$ v time).
What is the significance of the slope?

A
The slope represents the change in concentration over time.

B
The slope represents the inverse of change in concentration over time.

C
The slope represents the negative value of the rate constant.

D
The slope represents the negative rate of product concentration over time.

Solution

The slope represents the change in concentration over time showing in this diagram
digram is show the first order reaction
Question 9
1 / -0

Reacting $$Cl$$ with $$NO_{2}Cl$$ molecules produces $$NO_{2}$$ and $$Cl_{2}$$ gases.
Which of the following will require the lowest activation energy based on proper orientation for this reaction?

A

B

C

D

Solution

The atom collides to $$Cl$$ atom present in $$N{ O }_{ 2 }Cl$$. molecule with proper orientation & head or collision.
Therefore, very low activation energy is required.
Question 10
1 / -0

An experiment was performed to study the kinetics of the decomposition of substance $$X$$. The concentration of $$X$$, $$[X]$$, was monitored over time as the reaction proceeded. The data are shown in the table above. The time interval between concentration measurements was $$1.0\ minutes (60 s)$$.
Time (s) $$[X]$$ $$ln[X]$$ $$\dfrac {1}{[X]}$$
$$0$$ $$20.0$$ $$3.00$$ $$0.050$$
$$60$$ $$10.0$$ $$2.30$$ $$0.100$$
$$120$$ $$6.67$$ $$1.90$$ $$0.150$$
$$180$$ $$5.00$$ $$1.61$$ $$0.200$$
$$240$$ $$4.00$$ $$1.39$$ $$0.250$$
Which of the following best describes the reaction?

A
The decomposition of substance $$X$$ is a zero-order reaction.

B
The decomposition of substance $$X$$ is a first-order reaction.

C
The decomposition of substance $$X$$ is a second-order reaction.

D
The decomposition of substance $$X$$ is a third-order reaction.

Solution

Form the given data,
$$ \cfrac { 1 }{ [X] } \propto Time(t)\\ \therefore \cfrac { 1 }{ [X] } =Kt\longrightarrow $$ K=constant
$$ \therefore K=\cfrac { 1 }{ [X]t } $$
$$ \therefore$$ Unit of K are $${ M }^{ -1 }{ time }^{ -1 } $$ which is possible only for second order reaction

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Time (s)	$$[X]$$	$$ln[X]$$	$$\dfrac {1}{[X]}$$
$$0$$	$$20.0$$	$$3.00$$	$$0.050$$
$$60$$	$$10.0$$	$$2.30$$	$$0.100$$
$$120$$	$$6.67$$	$$1.90$$	$$0.150$$
$$180$$	$$5.00$$	$$1.61$$	$$0.200$$
$$240$$	$$4.00$$	$$1.39$$	$$0.250$$

Chemical Kinetics Test - 31

Result

Chemical Kinetics Test - 31

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Question 1

$$A$$

$$B$$

$$C$$

$$D$$

All reactions have equal activation energy

Solution

Question 2

The activation energy curve would grow taller.

The activation energy curve would grow shorter.

The activation energy curve would become inverted.

The activation energy curve would not be affected by an increase in temperature.

Solution

Question 3

The molecules were not in the proper states of matter.

The molecules did not have enough kinetic energy.

The molecules were not oriented correctly when they struck each other.

The temperature of the reaction mixture was not high enough.

Solution

Question 4

The value of activation energy varies from reaction to reaction.

If molecules are moving fast enough, the collisions will result in kinetic energy that can be used to bend, stretch, and eventually break the bonds of the reactants releasing the potential energy in a usable form.

All reactions eventually form an intermediate that lowers the overall energy requirements of the reaction resulting in a relatively reasonable activation energy.

Reactants only form products if the activation energy barrier has been exceeded with usable kinetic energy from the system and /or surroundings.

Solution

Question 5

$$[A]_{t} = -kt + [A]_{0}$$

$$ln [A]_{t} = -kt + ln [A]_{0}$$

$$\dfrac {1}{[A]_{t}} = kt + \dfrac {1}{[A]_{0}}$$

All of the above

None of the above

Solution

Question 6

Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

Assertion is true but Reason is false

Assertion is false but Reason is true

Both Assertion and Reason are false

Solution

Question 7

A step labeled fast

A step labeled moderate

A step labeled slow

It is not possible to tell which step is rate determining from this information.

Solution

Question 8

The slope represents the change in concentration over time.

The slope represents the inverse of change in concentration over time.

The slope represents the negative value of the rate constant.

The slope represents the negative rate of product concentration over time.

Solution

Question 9

Solution

Question 10

The decomposition of substance $$X$$ is a zero-order reaction.

The decomposition of substance $$X$$ is a first-order reaction.

The decomposition of substance $$X$$ is a second-order reaction.

The decomposition of substance $$X$$ is a third-order reaction.

Solution

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