States of Matter Test

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States of Matter Test - 73

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Question 1
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Directions For Questions

The apparatus shown consists of three temperature jacketed $$1.642$$ L bulbs connected by stopcocks. Bulb A contains a mixture of $$H_2O(g), CO_2(g)$$ and $$N_2(g)$$ at $$27^o$$C and a total pressure of $$570$$ mm Hg. Bulb B is empty and held at a temperature of $$-73^o$$C. Bulb C is also empty and is held at a temperature of $$-193^o$$C. The stopcocks are closed and the volume of the lines connecting the bulbs is zero. $$CO_2$$ sublimes at $$-78^o$$C and $$N_2$$ boils at $$-196^o$$C. Neglect the volume of any solid, if formed.

...view full instructions

How many moles of $$CO_2$$ are in the system?

A
$$0.0125$$

B
$$0.015$$

C
$$0.0225$$

D
$$0.0375$$
Question 2
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For an ideal solution of A and B , $$ Y_A $$ is the mole fraction of A in the vapour phase at equilibrium . which of the following plot should be linear ?

A
$$ P_{total} vs Y_A $$

B
$$ P_{total} vs Y_B $$

C
$$ \frac {1}{P_{total } } vs Y_A $$

D
$$ \frac {1}{P_{total} } vs \frac {1}{Y_A } $$

Solution
Question 3
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A liquid solution is formed by mixing 10 moles of anline and 20 moles of phenol at a temperature where the vapour phenol are 90 and 897 mm Hg, respectively . The possible vapour pressure of solution at that temperature is ?

A
82 mm Hg

B
88 mm Hg

C
90 mm Hg

D
94 mm Hg

Solution
Question 4
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A mixture contains 1 mole of volatile liquid $$ A (P^0_A = 100 mm Hg ) $$ and 3 moles of volatile liquid$$ B (P^0_B = 80 mm Hg ) $$ if the solution behaves ideally, the total vapour pressure of the distillate is

A
85 mm Hg

B
85.88 mm Hg

C
90 mm Hg

D
92 mm Hg

Solution

Mole fraction of A is $$X_A=\frac{1}{1+3}=0.25$$
Mole fraction of B is $$X_B=1-0.25=0.75$$

The expression for the total pressure of the solution is
$$P=P_A^0X_A+P_B^0X_B$$

Substitute values in the above expression
$$P=100\times 0.25+80\times 0.75=85$$ mm of Hg
Hence the correct answer is [A]
Question 5
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An aqueous solution of sucrose is 0.5 molal. What is the vapour pressure of water above this solution ? The vapour pressure of pure water is 25.0 mm Hg at this temperature.

A
24.8 mm Hg

B
0.45 mm Hg

C
2.22 mm Hg

D
20.3 mm Hg

Solution

Given that
$$ m = 0.5\;\;molal $$
V.P. (pure water) 25.0mm Hg

According to the Raoult's law for dilute solution
$$\dfrac{P_0 - P_s}{P_0} = \dfrac{w}{m+W}\times 1000 = X_{sucrose}$$

here the 0.5 molal of solution means 0.5 mole in 1kg of water
Henc the mole of solvent = $$\dfrac{1000}{18}=55.5$$ [ the molecular mass of water molecules is 18]

then $$ \dfrac{25-P_s}{25} = \dfrac{0.5}{55.57+0.5}$$

$$ \Rightarrow\;1401.75 - 56.07P_s = 12.5 $$

$$\Rightarrow \; 56.07P_s = 1407.75 - 12.5$$

$$\Rightarrow \; P_S = \dfrac{1389.25}{\;\;56.07}$$

$$24.8\;mm \;Hg$$
Question 6
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Directions For Questions

The composition of vapour over a binary ideal solution is determined by the composition of the liquid . $$ X_A and Y_A $$ are the mole fraction of A i the liquid and vapour at equilibrium respectively.

...view full instructions

The vapour pressure of the solution this composition is:

A
$$ \sqrt { P^0_A .P^0_B } $$

B
$$ ( P^0_A - P^0_B ) $$

C
$$ ( P^0_A + P^0_B ) $$

D
$$ 0.5 ( P^0_A + P^0_B ) $$

Solution
Question 7
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A liquid mixture of A and B (assume ideal solution ) is placed in a cylinder and piston arrangement . The piston is slowly pulled out isothermally so that the volume of liquid decreases and that of vapour increases. at the instant when the quantity of the liquid still remaining is negligibly small, the mole fraction of 'A' in the vapour is 0.4 .If $$ P^0_A = 0.4 atm , P^0_B = 1.2 atm $$ at this temperature, the total pressure at which the liquid has almost evaporated is ?

A
0.667 atm

B
1.5 atm

C
0.8 atm

D
0.545 atm

Solution
Question 8
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Benzene and toulene from an ideal solution, the vapour pressures of the benzene and toluene are 75 mm and 25 mm respectively at $$ 20^0 C $$ if the mole fractions of benzene and toluene in vapour are 0.75 and 0.25 respectively the vapour pressure of the ideal solution is

A
62.5 mm

B
50 mm

C
30 mm

D
40 m

Solution
Question 9
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Liquids A and B from an ideal solution. A certain solution of A and B contains 25 mole percent of A whereas the vapours in the equilibrium with the solution at 298 K contains 50 mole per cent of A. The ratio of vapour pressures of pure A to that of pure B at 298 K , is

A
1 :1

B
3 : 1

C
1 :3

D
2 :1

Solution
Question 10
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The ratio between lowering of vapour pressure of solution and mole fraction of solute is equal to

A
relative lowering of vapour pressure

B
vapour pressure of pure solvent

C
vapour pressure of solution

D
molar mass of solvent

Solution