Solutions Test -21

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Solutions Test -21

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Question 1
1 / -0

Colligative properties depend on .........

A
The nature of the solute particles dissolved in solution

B
The number of solute particles in solution.

C
The physical properties of the solute particles dissolved in solution.

D
The nature of solvent particles.

Solution

The number of solute particles in solution.
Question 2
1 / -0

In comparison to a 0.01 M solution of glucose, the depression in freezing point of a $0.01\,M\,MgCl_2$ solution is

A
The same

B
About twice

C
About three times

D
About six times

Solution

Depression in freezing point is a colligative property . In case of $MgCl_2$ value of van’t. Hoff factor will be more. No. of ions yielded when a molecule of $MgCl_2$ gets dissociated in its aqueous solution is = 3 . Thus one molecule of $0.01M \,MgCl_2$ gives out three particles / ions in solution , thereby increasing the number of particles present in its solution to three times . It is because of this that depression in freezing point of $0.01M\,MgCl_2$ will be three times as compared to that of 0.01M - glucose solution , where no dissociation of the molecule takes place..
Question 3
1 / -0

An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because ..............

A
It gains water due to osmosis.

B
It loses water due to reverse osmosis.

C
It gains water due to reverse osmosis.

D
It loses water due to osmosis.

Solution

When an unripe mango is placed in a concentrated salt solution to prepare pickle then mango loose water due to osmosis and get shrivel.
Question 4
1 / -0

At a given temperature, osmotic pressure of a concentrated solution of a substance

A
Is higher than that at a dilute solution.

B
Is lower than that of a dilute solution.

C
Is same as that of a dilute solution.

D
Cannot be compared with osmotic pressure of dilute solution.

Solution

According to definition of osmotic pressure we know that n = CRT. For concentrated solution C has higher value than dilute solution. Hence, as concentration of solution increases osmotic pressure will also increase.
Question 5
1 / -0

Which of the following statements is false?

A
Units of atmospheric pressure and osmotic pressure are the same.

B
In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.

C
The value of molal depression constant depends on nature of solvent.

D
Relative lowering of vapour pressure, is a dimensionless quantity.

Solution

In reverse osmosis solvent molecules move through a semipermeable membrane from a region of higher concentration of solute to a region of lower concentration , therefore the given statement at (ii) is false.
Question 6
1 / -0

Value of Henry’s constant $K_H$ ...........

A
Increases with increase in temperature.

B
Decreases with increase in temperature.

C
Demains constant

D
First increases then decreases.

Solution

Value of Henry's constant (KH) increases with increase in temperature representing the decrease in solubility.
Question 7
1 / -0

The value of Henry’s constant $K_H$ is

A
Greater for gases with higher solubility.

B
Greater for gases with lower solubility.

C
Constant for all gases.

D
Not related to the solubility of gases.

Solution

The value of Henry's constant $K_H$ is greater for gases with lower solubility because of the mathematical relation

$P\,=\,k_H \,x$

$k_H\, = \,p/x $

where ,$ K_H$ represents Henry's constant , p is partial pressure of the gas in vapour phase , and x denotes mole fraction of the gas in solution.Thus $K_H$ is inversely proportional to mole fraction of gas in solution (representing its solubility).
Question 8
1 / -0

We have three aqueous solutions of NaCl labelled as ‘A’, ‘B’ and ‘C’ with concentrations 0.1M, 0.01M and 0.001M, respectively. The value of van’t Hoff factor for these solutions will be in the order .............

A
$i_A\,< i_B\,< i_C$

B
$i_A\,>\,i_B\,>\,i_C$

C
$i_A\,=\,i_B\,= \,i_C$

D
$i_A\,< \,i_B\,> \,i_C$

Solution

It is because the extent or degree of dissociation increases with increase in dilution of a solution. 0.001M NaCl solution 'C' is most diluted as compared to the other two NaCl solutions. The vant Hoff factor ( i ) depends on extent of dilution.
Question 9
1 / -0

Isotonic solutions must have the same .........

(i) solute

(ii) density

(iii) elevation in boiling point

(iv) depression in freezing point

A
(ii) and (iii)

B
(i) and (iii)

C
(iii) and (iv)

D
(i) and (iv)

Solution

Isotonic solutions have same osmotic pressure and same concentration. Elevation in boiling point and depression in freezing point are the colligative properties. These two colligative properties depend upon concentration. As the molar concentration is same for isotonic solutions, so elevation in boiling point and depression in freezing point of isotonic solutions must be same.
Question 10
1 / -0

Which of the following binary mixtures will have same composition in liquid and vapour phase?

(i) Benzene - Toluene

(ii) Water-Nitric acid

(iii) Water-Ethanol

(iv) n-Hexane - n-Heptane

A
(ii) and (iii)

B
(ii) and (i)

C
(iv) and (i)

D
(ii) and (iv)

Solution

At particular composition Water-Nitric acid and water-Ethanol form azeotropic mixture which have same composition in vapour phase and liquid phase.
Question 11
1 / -0

The van't Hoff factor (i) for a dilute aqueous solution of the strong electrolyte barium hydroxide is :

A
2

B
3

C
0

D
1

Solution

Hint: For strong electrolytes, Van't Hoff factor $$(i)$$ is equal to the number of ions produced.

Formula:
$$\alpha = \dfrac {i-1} {n-1}$$
Here, $$\alpha$$ is the degree of dissociation,
$$i$$ van't Hoff factor and
$$n$$ is number of ions.

Step 1: To find the number of ions in barium hydroxide.
$$Ba(OH)_{2}$$ is a strong electrolyte that dissociates $$100$$% in an aqueous medium as

$$Ba(OH)_{2} (l) \leftrightarrow Ba^{2+} (aq) + 2OH^{-} (aq)$$
So,
Number of ions $$n=1+2=3$$

Step 2: To find the van't Hoff factor $$(i)$$ for barium hydroxide.
As barium hydroxide is a strong electrolyte,
$$\therefore $$ $$\alpha=1$$
Using formula,
$$\alpha = \dfrac {i-1} {n-1}$$

$$1 = \dfrac {i-1} {3-1}$$

$$(i-1) = 2$$

$$i=2+1$$

$$i=3$$

Final answer:
Option $$B$$ is the correct answer.
Question 12
1 / -0

In case of an electrolyte which dissociates in the solution, the van't hoff factor $$i$$ is :

A
$$>1$$

B
$$<1$$

C
$$1$$

D
$$>1 \ or \ <1$$

Solution

We know that,
$$ i = \dfrac{ number\: of\: molecules\: after\: association/dissociation }{ number\: of\: molecules\: before\: association/dissociation } $$
After dissociation number of molecules increases. Therefore i>1
Question 13
1 / -0

Correct combination among the following is
i) Water can be converted into vapour at $${ 100 }^{ 0 }C$$ only
ii) Vapour pressure can be increased more than the atmospheric pressure at a certain temperature.
iii) Lowering of vapour pressure is directly proportional to mole fraction of solute.

A
All are correct

B
ii only wrong

C
iii only correct

D
All are wrong

Solution

Using clausius clapeyron equation,
we get $$ log \dfrac{P_2}{P_1} = -\dfrac{\Delta H}{R} \times (\dfrac{1}{T_1} - \dfrac{1}{T_2}) $$
Therefore, at any particluar temperature, the vapour pressure of solution is unique.
Also, conversion to vapour of a liquid can take place at many temperatures and many pressure values.
The third statement is the outcome of Raoult's law.
Question 14
1 / -0

Which of the following solutions will have the maximum lowering of vapour pressure ?

A
1M - $${ CaCl }_{ 2 }$$

B
1M-$$NaCl$$

C
1N - $$Phenol$$

D
1M - $$Sucrose$$

Solution

Since the some compounds in the options are ionic, the maximum lowering is decided as per the highest vant hoff factor.
For calcium chloride ,V.H. factor $$=$$ 3
For salt,V .H. factor $$=$$ 2
For phenol , V.H. factor < 1 (molecules associate)
For sucrose , factor $$=$$ 1.
Question 15
1 / -0

A solution is obtained by dissolving 12g of urea (Mol.wt.=60) in a litre of solution. Another solution is prepared by dissolving 68.4g of cane sugar(Mol.wt.=342) in a litre of solution at the same temperature. The lowering of vapour pressure in the first solution is:

A
nearly 5 times that of the second solution

B
same as that of second solution

C
double that of second solution

D
nearly one fifth of the second solution

Solution

For urea $$\Delta P_1=X_{urea}P^0$$

$$\Delta P_1=\dfrac {\dfrac {12}{60}}{total \ mole}P^0$$

$$\Delta P_1=\dfrac {0\cdot 2}{total \ mole} P^0$$ ----(1)

For sugar $$\Delta P_2=X_{sugar}P^0$$

$$\Delta P_2=\dfrac {\dfrac {68\cdot 4}{342}}{total \ mole}P^0$$

$$\Delta P_2=\dfrac {0\cdot 2}{total \ mole} P^0$$ ----(2)

Hence $$(1)=(2)$$

Hence, the correct option is $$B$$
Question 16
1 / -0

For a non-electrolytic solution, vant Hoff factor is equal to :

A
0

B
1

C
between 0 and 1

D
none of the above

Solution

The van't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van't Hoff factor is essentially $$1$$.
Question 17
1 / -0

For a substance $$A$$ when dissolved in a solvent $$B$$ shows the molecular mass corresponding to $${ A }_{ 3 }$$. The van't Hoff factor will be:

A
$$1$$

B
$$2$$

C
$$3$$

D
$$\dfrac{1}{3}$$

Solution

$$3A\rightarrow A_{3}$$

3 moles of A associate to form 1 mole as A solute undergoes trimerization so van't Hoff factor $$\dfrac{1}{3}$$.

Hence, the correct option is $$D$$
Question 18
1 / -0

In case a solute associates in solution, the van’t Hoff factor is :

A
$$i > 1$$

B
$$i = 1$$

C
$$i < 1$$

D
None of these

Solution

if a fraction $${\displaystyle \alpha }$$ of $${\displaystyle n}$$ moles of solute associate to form one mole of an n-mer (dimer, trimer, etc.), then

$${\displaystyle i=1-\left(1-{\frac {1}{n}}\right)\alpha .}$$

For the dimerisation of acetic acid in benzene

$$2CH_3COOH ⇌ {(CH_3COOH)}_2$$

2 moles of acetic acid associate to form 1 mole of dimer, so that

$${\displaystyle i=1-\left(1-{\frac {1}{2}}\right)\alpha =1-{\frac {\alpha }{2}}.}$$

For association in the absence of dissociation, the van 't Hoff factor is: $${\displaystyle i<1}$$

Hence, the correct option is $$\text{C}$$
Question 19
1 / -0

For a very dilute aqueous solution of $${ K }_{ 4 }\left[ Fe\left( CN \right) _{ 6 } \right] $$ , van't Hoff factor is :

A
$$i=11$$

B
$$i=5$$

C
$$i=\dfrac { 1 }{ 11 } $$

D
$$i=10$$

Solution

Considering complete dissociation,
$$ K_4[Fe(CN)_6] \rightarrow 4K^+ + [Fe(CN)_6]^{4-} $$

$$ i = 5 $$
Question 20
1 / -0

The van't Hoff factor for a very dilute aqueous solution of $$K\left[Ag\left( CN \right) _{ 2 } \right] $$ is:

A
$$4$$

B
$$3$$

C
$$2$$

D
$$5$$

Solution

$$K[Ag(CN)_{2}]$$ dissociate into $$K^{+}$$ and $$ [Ag(CN)_{2}]^{-}$$

So $$i=1+1=2$$.

Hence, the correct option is $$\text{C}$$

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Solutions Test -21

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Solutions Test -21

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SHARING IS CARING

Question 1

The nature of the solute particles dissolved in solution

The number of solute particles in solution.

The physical properties of the solute particles dissolved in solution.

The nature of solvent particles.

Solution

Question 2

The same

About twice

About three times

About six times

Solution

Question 3

It gains water due to osmosis.

It loses water due to reverse osmosis.

It gains water due to reverse osmosis.

It loses water due to osmosis.

Solution

Question 4

Is higher than that at a dilute solution.

Is lower than that of a dilute solution.

Is same as that of a dilute solution.

Cannot be compared with osmotic pressure of dilute solution.

Solution

Question 5

Units of atmospheric pressure and osmotic pressure are the same.

In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.

The value of molal depression constant depends on nature of solvent.

Relative lowering of vapour pressure, is a dimensionless quantity.

Solution

Question 6

Increases with increase in temperature.

Decreases with increase in temperature.

Demains constant

First increases then decreases.

Solution

Question 7

Greater for gases with higher solubility.

Greater for gases with lower solubility.

Constant for all gases.

Not related to the solubility of gases.

Solution

Question 8

\(i_A\,< i_B\,< i_C\)

\(i_A\,>\,i_B\,>\,i_C\)

\(i_A\,=\,i_B\,= \,i_C\)

\(i_A\,< \,i_B\,> \,i_C\)

Solution

Question 9

(ii) and (iii)

(i) and (iii)

(iii) and (iv)

(i) and (iv)

Solution

Question 10

(ii) and (iii)

(ii) and (i)

(iv) and (i)

(ii) and (iv)

Solution

Question 11

2

3

0

1

Solution

Question 12

$$>1$$

$$<1$$

$$1$$

$$>1 \ or \ <1$$

Solution