Surface Chemistry Test

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Surface Chemistry Test - 25

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Weekly Quiz Competition

Question 1
1 / -0

An uncatalyzed reaction' s progress diagram is shown by solid line. Which of two dotted lines represents the same reaction in the presence of catalyst?

A
A

B
B

C
C

D
D

E
E

Solution

The dotted line B represents the same reaction in the presence of catalyst. The catalyst provides alternate pathway of lower activation energy.
Question 2
1 / -0

The change in energy for the overall reaction is defined by letter :

A
A

B
B

C
C

D
Y

E
X

Solution

The change in energy for the overall reaction is defined by letter C.
It represents the difference in the energy of products and the energy of reactants.
Question 3
1 / -0

Activation energy of the reaction is corresponded by letter :

A
A

B
B

C
C

D
Y

E
X

Solution

The activation energy of the reaction is corresponded by letter A.
It is the difference in the energy of transition state and the energy of ground state. (Reactant).
Question 4
1 / -0

A catalyst:

A
changes ΔG for an equation

B
acts by increasing the rate of the forward reaction more than the reverse reaction

C
raises the equilibrium constant of a system

D
may have a molecular weight as low as 1 or higher than 200,000

Solution

A catalyst :
$$\bullet $$ does not change $$\Delta G$$ for a reaction.
$$\bullet $$ acts by increasing the rate of forward reaction and backward reaction by equal amounts.
$$\bullet $$ does not affect the value of equilibrium constant.
$$\bullet $$ may have a molecular weight as low as 1 or higher than 200,000.
$$\therefore $$ The only correct choice is that a catalyst may have a molecular weight as low as 1 or higher than 200,000.
Question 5
1 / -0

A catalyzed reaction mechanism has a ____ activation energy and thus, causes a _____ reaction rate.

A
higher, lower

B
higher, higher

C
lower, higher

D
lower, steady

E
higher, steady

Solution

In a catalyzed reaction, mechanism has a lower activation energy and thus, causes a higher reaction rate. Thus, a catalyst provides an alternate pathway having lower activation energy.
Question 6
1 / -0

A catalyst :

A
Changes $$\displaystyle \Delta G$$ for an equation

B
Acts by increasing the rate of the forward reaction more than the reverse reaction

C
Raises the equilibrium constant of a system

D
May have molecular weight as low as 1 or higher than 200,000

E
Does not react chemically during the course of a reaction

Solution

R.E.F image
Characteristics of catalyst are as follows:
1. The catalyst remains unchanged (in mass and chemical composition ) in the reaction (Activity of catalyst)
2. A small quantity of the catalyst is required. e.g. one mole of colloid pt catalyses $$ 10^{8}LH_{2}O_{2} $$
3. The catalyst does not change the equilibrium constant. But the equilibrium approaches earlier.
4. Specificity of catalyst:
The catalyst is specific in nature. It means by the change of catalyst, nature of the product changes or
specific catalyst for a specific reaction.
5. The catalyst can not make impossible reaction to occur and does not initiate a reaction.
Question 7
1 / -0

Statement I: Above reaction is exothermic.
Because
Statement II: Energy difference B is greater than energy difference A.

A
true, true, correct explanation

B
true, true, not correct explanation

C
true, false

D
false, true

E
false, false

Solution

Statement I: Above reaction is exothermic as the energy of products is lower than the energy of reactants.
Statement II: Energy difference B is greater than energy difference A as the energy of products is lower than the energy of reactants.

The energy difference B corresponds to the difference in the energy of products and transition state.
Energy difference A corresponds to the difference in the energy of transition state and reactants.
Both statements are true and second statement is correct explanation of the first statement.
Question 8
1 / -0

Recorded data:
Before$$:$$ $$CuO+$$porcelain boat$$=62.869$$g
$$CaCl_2+$$U-tube$$=80.483$$g
After:Porcelain boat$$+$$contents $$=54.869$$g
$$CaCl_2+$$U-tube$$=89.483$$g
Reactions:$$Zn(s)+2HCl(aq)\rightarrow ZnCl_2(aq)+H_2(g)$$ then $$H_2(g)+CuO(s)\rightarrow H_2O(g)+Cu(s)$$
What was the reason placing tube of $$CaCl_2$$ between the generator and the tube containing the porcelain boat?

A
To absorb evaporated HCl

B
To absorb evaporated $$H_2O$$

C
To slow down the gases released

D
To absorb the evaporated Zn particles

E
To remove the initial air that passes through the tube

Solution

A tube of $$\displaystyle CaCl_2$$ was placed between the generator and the tube containing the porcelain boat to absorb evaporated $$\displaystyle H_2O$$. $$\displaystyle CaCl_2$$ is a drying agent. It removes moisture from hydrogen gas.
Question 9
1 / -0

After observing the graph, which statement tells that the chemical reaction is exothermic?

A
The potential energy at point 2

B
The energy difference between points 1 and 2

C
The time elapsed between points 2 and 3

D
The energy difference between points 1 and 3

E
The time needed to reach point 3

Solution

The energy difference between points 1 and 3 tells that the chemical reaction is exothermic.
The energy at point 1 is higher than the energy at point 3.
Hence, when the reaction proceeds, heat is given out.
Hence, the reaction is exothermic.
Question 10
1 / -0

Which of the following pairs of colloidal solutions have dispersed phase as liquid and dispersed medium as gas?

A
Fog, mist

B
Butter, milk

C
Fog, smoke

D
Smoke, foam

Solution

Fog: Dispersed phase - Liquid and Dispersed medium - Gas
Mist: Dispersed phase - Liquid and Dispersed medium - Gas
Butter: Dispersed phase - Liquid and Dispersed medium - Solid
Milk: Dispersed phase - Liquid and Dispersed medium - Liquid
Smoke: Dispersed phase - Solid and Dispersed medium - Gas