Solutions Test 45

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Solutions Test 45

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Weekly Quiz Competition

Question 1
1 / -0

The vapour pressure lowering caused by the addition of $$100 \,g$$ of sucrose (molecular mass = 342) to $$1000 \,g$$ of water if the vapour pressure of pure water at $$25 ^\circ C$$ is $$23.8 \,mm \,Hg$$

A
$$1.25 \,mm \,Hg$$

B
$$0.125 \,mm \,Hg$$

C
$$1.15 \,mm \,Hg$$

D
$$00.12 \,mm \,Hg$$

Solution

Given molecular mass of sucrose $$= 342$$

Moles of sucrose $$= \dfrac {100}{342} = 0.292 \,mole$$

Moles of water $$N = \dfrac {1000}{18} = 55.5 \,moles $$ and

Vapour pressure of pure water $$P^{0} = 23.8 \,mm \,Hg$$

According to Raoult's law

$$\dfrac {\Delta P}{P^{0}} = \dfrac {n}{n + N} \Rightarrow \dfrac {\Delta P}{23.8} = \dfrac {0.292}{0.292 + 55.5}$$

$$\Delta P = \dfrac {23.8 \times 0.292}{55.792} = 0.125 \,mm \,Hg$$
Question 2
1 / -0

$$5 \,cm^3$$ of acetone is added to $$100 \,cm^3$$ of water, the vapour pressure of water over the solution

A
It will be equal to the vapour pressure of pure water

B
It will be less than the vapour pressure of pure water

C
It will be greater than the vapour pressure of pure water

D
It will be very large

Solution

Acetone solution has a vapour pressure less than pure water since the number of water molecules exposed to the surface will be less after mixing.
Question 3
1 / -0

Which property is shown by an ideal solution

A
It forms Raoult's law

B
$$\Delta H_{mix} = 0$$

C
$$\Delta V_{mix} = 0$$

D
All of these
Solution
Ideal Solutions generally have characteristics as follows:
$$\text{They follow Raoult’s Law.}$$
$$\text{The enthalpy of mixing of two components should be zero, that is, } Δmix H = 0.$$ This signifies that no heat is released or absorbed during mixing of two pure components to form an ideal solution
$$\text{The volume of the mixing is equal to zero that is, ΔmixV = 0.}$$ This means that total volume of solution is exactly same as the sum of the volume of solute and solution. Adding further, it also signifies that there will be contraction or expansion of the volume while the mixing of two components is taking place.
The solute-solute interaction and solvent-solvent interaction is almost similar to the solute-solvent interaction.
Question 4
1 / -0

Which has maximum vapour pressure?

A
$$HI$$

B
$$HBr$$

C
$$HCl$$

D
$$HF$$

Solution

The lower is boiling point more is the vapour pressure. Boiling point order is $$HCl < HBr < HI < HF$$
Question 5
1 / -0

All form ideal solution except

A
$$C_2H_5Br$$ and $$C_2H_5I$$

B
$$C_2H_5Cl$$ and $$C_6H_5Br$$

C
$$C_6H_6$$ and $$C_6H_5CH_3$$

D
$$C_2H_5I$$ and $$C_2H_5OH$$

Solution
Question 6
1 / -0

An example of near ideal solution is

A
n-heptane and n-hexane

B
$$CH_3COOH + C_5H_5N$$

C
$$CHCl_3 + (C_2H_5)_2O$$

D
$$H_2O + HNO_3$$

Solution
Question 7
1 / -0

Which of the following solution in water possesses the lowest vapour pressure?

A
$$0.1 (M) NaCl$$

B
$$0.1 (M) BaCl_2$$

C
$$0.1 (M) KCl$$

D
None of these

Solution

The molarity for all the options is same i.e. 0.1 M, thus the deciding factor would be 'i'
in A, i = 2
in B, i = 3
in C, i = 2

This implies that dissociation into ions is maximum in the case of B, and thus least vapour pressure is observed
Question 8
1 / -0

Which property is not found in ideal solution

A
$$P_A \neq P^0_A \times X_A$$

B
$$\Delta H_{mix} \neq 0$$

C
$$\Delta V_{mix} \neq 0$$

D
All of these
Solution
Ideal Solutions generally have characteristics as follows:
$$\text{They follow Raoult’s Law.}$$ This implies that the partial pressure of components A and B in a solution will be $$P_A = P_A^0\times X_A$$.
The enthalpy of mixing of two components should be zero, that is, $$Δmix H = 0.$$ This signifies that no heat is released or absorbed during mixing of two pure components to form an ideal solution
The volume of the mixing is equal to zero that is, $$Δmix V = 0.$$ This means that the total volume of solution is exactly the same as the sum of the volume of solute and solution. Adding further, it also signifies that there will be contraction or expansion of the volume while the mixing of two components is taking place.
The solute-solute interaction and solvent-solvent interaction are almost similar to the solute-solvent interaction.
thus, the correct answer is D.
Question 9
1 / -0

The Van't Hoff factor will be highest for:

A
Sodium chloride

B
Magnesium chloride

C
Sodium phosphate

D
Urea

Solution

As the Van't Hoff factor depends on number of ions or particles produced on dissociation.
$$i_{NaCl}=2$$
$$i_{MgCl_2}=3$$
$$i_{Na_3PO_4}=4$$
$$i_{urea}=1$$

thus, the correct answer is C.
Question 10
1 / -0

Which of the following salt has the same value of Van't Hoff factor i as that of $$K_3 [Fe(CN)_6]$$?

A
$$Al_2(SO_4)_3$$

B
$$NaCl$$

C
$$Na_2SO_4$$

D
$$Al(NO_3)_3$$

Solution

Van't Hoff factor of $$K_3[Fe(CN)_6]$$

$$K_3[Fe(CN)_6]\rightarrow 3K^+ + [Fe(CN)_6]^-$$
$$i=4$$

$$i_{Al_2(SO_4)_3}=5$$
$$i_{NaCl}=2$$
$$i_{Na_{SO_4}}=3$$
$$i_{Al_2(NO_3)_3}=4$$

thus, the correct answer is D.

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Re-Attempt Weekly Quiz Competition

Solutions Test 45

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Solutions Test 45

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SHARING IS CARING

Question 1

$$1.25 \,mm \,Hg$$

$$0.125 \,mm \,Hg$$

$$1.15 \,mm \,Hg$$

$$00.12 \,mm \,Hg$$

Solution

Question 2

It will be equal to the vapour pressure of pure water

It will be less than the vapour pressure of pure water

It will be greater than the vapour pressure of pure water

It will be very large

Solution

Question 3

It forms Raoult's law

$$\Delta H_{mix} = 0$$

$$\Delta V_{mix} = 0$$

All of these

Solution

Question 4

$$HI$$

$$HBr$$

$$HCl$$

$$HF$$

Solution

Question 5

$$C_2H_5Br$$ and $$C_2H_5I$$

$$C_2H_5Cl$$ and $$C_6H_5Br$$

$$C_6H_6$$ and $$C_6H_5CH_3$$

$$C_2H_5I$$ and $$C_2H_5OH$$

Solution

Question 6

n-heptane and n-hexane

$$CH_3COOH + C_5H_5N$$

$$CHCl_3 + (C_2H_5)_2O$$

$$H_2O + HNO_3$$

Solution

Question 7

$$0.1 (M) NaCl$$

$$0.1 (M) BaCl_2$$

$$0.1 (M) KCl$$

None of these

Solution

Question 8

$$P_A \neq P^0_A \times X_A$$

$$\Delta H_{mix} \neq 0$$

$$\Delta V_{mix} \neq 0$$

All of these

Solution

Question 9

Sodium chloride

Magnesium chloride

Sodium phosphate

Urea

Solution

Question 10

$$Al_2(SO_4)_3$$

$$NaCl$$

$$Na_2SO_4$$

$$Al(NO_3)_3$$

Solution

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