Surface Chemistry Test

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Surface Chemistry Test - 15

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Question 1
1 / -0

Which is not correct for an oil-water emulsion?

A
It imparts dye colour with water soluble dye.

B
It can be diluted with water.

C
It has higher viscosity in comparison to water-oil emulsion.

D
It consists of vanishing cream.

Solution
Question 2
1 / -0

Which type of metals form effective catalysts?

A
Alkali metals

B
Transition metals

C
Alkaline earth metals

D
Radioactive metals

Solution

Transition metals are more effective catalysts on account of their larger surface area and half-filled and partially filled nature of penultimate d-subshells.

Also, they are more effective due to their variable valency.

Option B is correct.
Question 3
1 / -0

Bredig's arc method involves :

A
dispersion

B
condensation

C
peptization

D
dispersion and condensation both

Solution

First of all on passing electric arc, metal vapours are formed (dispersion) which are than condensed in water to form sol particles.
Question 4
1 / -0

About positive and negative catalyst, which of the following statements is incorrect?

A
Positive catalyst lowers the energy of activation

B
Negative catalyst decreases the energy of activation

C
Positive catalyst increases the rate of reaction

D
Negative catalyst functions to remove active intermediates

Solution

Positive catalyst: A catalyst which increases the rate of reaction is called positive catalyst. Such catalyst decreases activation energy by accepting a smaller path, so rate of reaction is increased.

Negative catalyst (Inhibitor): A catalyst which decreases or retards the rate of reaction is called negative catalyst. It is because a negative catalyst increases activation energy by taking a longer alternative path. Also, it combines with reactant molecules and decreases the number of colliding reactant molecules.

Hence, option (B) is the incorrect statement.
Question 5
1 / -0

What type of bond would exist between this soap and oil?

A
Hydrogen bonds

B
Dispersion forces

C
Covalent bonds

D
Dipole-dipole forces

Solution

The soap contains two parts, one is polar carboxylic group which interacts with polar water molecules through strong electrostatic forces of attraction.

The other part is non polar hydrocarbon tail which interacts with oil through dispersion forces.

The non-polar hydrocarbon tail interacts with non-polar substances through dispersion forces, whilst the polar head interacts with polar substances (normally water) which forms dipole-dipole interactions and hydrogen bonds with water.

Option B is correct.
Question 6
1 / -0

An emulsion is a colloidal system of ____________:

A
two solids

B
two liquids

C
one gas and one solid

D
one gas and one liquid

Solution

Emulsion is type of colloid where dispersed phase is liquid and dispersion phase is liquid. Examples are milk and cream.
Question 7
1 / -0

Cleansing action of soap occurs because:

A
oil and grease can be absorbed into the hydrophobic centres of soap micelles and washed away

B
oil and grease can be absorbed into hydrophilic centres of soap micelles and washed away

C
oil and grease can be absorbed into both hydrophilic and hydrophobic centres but cannot be washed away

D
cleansing action is not related to micelles
Question 8
1 / -0

When oil and water are into the same vessel, two layers are observed with the less dense oil on top. These two liquids are said to be:

A
hydrophilic

B
hydrophobic

C
insoluble

D
immiscible

Solution

When oil and water are into the same vessel, two layers are observed with the less dense oil on top. These two liquids are said to be immiscible. Liquids tend to be immiscible when the force of attraction between the molecules of the same liquid is greater than the force of attraction between the two different liquids.

Oils are typically nonpolar carbon-based molecules with high molecular weights. As a result, there are strong dispersion forces between the molecules in an oil.

Water molecules interact strongly by hydrogen bonding, so (if we consider water to be the solvent and oil the solute), we would say that there are strong solvent-solvent interactions (H bonding) and strong solute-solute interactions (dispersion forces between rather large molecules) but the solvent-solute interaction (dispersion interaction between water and 'oil') is sufficiently weak.
Question 9
1 / -0

Which gas will be adsorbed on a solid to greater extent?

A
A gas having non polar molecule.

B
A gas having highest critical temperature $$\displaystyle \left ( T_{c} \right )$$.

C
A gas having lowest critical temperature.

D
A gas having highest critical pressure.

Solution

The critical temperature of a substance is the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied.

So, the higher the critical temperature of a gas, the higher will be the extent of adsorption. But, a gas having a non-polar molecule will have weak forces for bonding than an ionic molecule. So, it will adsorb less.
Question 10
1 / -0

Cod liver oil is:

A
fat dispersed in water

B
water dispersed in fat

C
water dispersed in oil

D
fat dispersed in fat

Solution

Hint: A colloidal solution of liquid in liquid is called an emulsion.
Correct Answer: Option C

Explanation:

Emulsions can be categorized into two types depending upon the dispersion medium and dispersed phase. They are oil dispersed in water and water dispersed in oil.
In cod liver oil, the dispersion medium is oil, and the dispersed phase is water.

Hence, cod liver oil is an example of an emulsion of type water dispersed in oil.

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Surface Chemistry Test - 15

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Surface Chemistry Test - 15

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SHARING IS CARING

Question 1

It imparts dye colour with water soluble dye.

It can be diluted with water.

It has higher viscosity in comparison to water-oil emulsion.

It consists of vanishing cream.

Solution

Question 2

Alkali metals

Transition metals

Alkaline earth metals

Radioactive metals

Solution

Question 3

dispersion

condensation

peptization

dispersion and condensation both

Solution

Question 4

Positive catalyst lowers the energy of activation

Negative catalyst decreases the energy of activation

Positive catalyst increases the rate of reaction

Negative catalyst functions to remove active intermediates

Solution

Question 5

Hydrogen bonds

Dispersion forces

Covalent bonds

Dipole-dipole forces

Solution

Question 6

two solids

two liquids

one gas and one solid

one gas and one liquid

Solution

Question 7

oil and grease can be absorbed into the hydrophobic centres of soap micelles and washed away

oil and grease can be absorbed into hydrophilic centres of soap micelles and washed away

oil and grease can be absorbed into both hydrophilic and hydrophobic centres but cannot be washed away

cleansing action is not related to micelles

Question 8

hydrophilic

hydrophobic

insoluble

immiscible

Solution

Question 9

A gas having non polar molecule.

A gas having highest critical temperature $$\displaystyle \left ( T_{c} \right )$$.

A gas having lowest critical temperature.

A gas having highest critical pressure.

Solution

Question 10

fat dispersed in water

water dispersed in fat

water dispersed in oil

fat dispersed in fat

Solution

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