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CBSE Questions for Class 11 Medical Chemistry States Of Matter Gases And Liquids Quiz 15 - MCQExams.com
CBSE
Class 11 Medical Chemistry
States Of Matter Gases And Liquids
Quiz 15
Two liquids A and B form an ideal solution. the solution has a vapor pressure of 700 torrs at $$ 80^0 C $$. it is distilled till 2/3rd of the solution is collected as condensate. the composition of the condensate $$ x'_A = 0.75 $$. and that of residue is $$ x''_A = 0.30 $$ if the vapor pressure of the residue at $$ 80^0 C $$ is 600 torr. which of the following is/are true?
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The composition of the original liquid was $$ x_A = 0.6 $$
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The composition of the original liquid was $$ x_A = 0.4 $$
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$$ P^0_A = \frac {2500}{3} Torr $$
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$$ P^0_B = 500 Torr $$
Explanation
$$ x_AP^0_A + x_B P^0_B = 700 ......(i) $$
$$ X_A "P^0_A + X^"_B P^0_B = 0.30 P^0_A + 0.70 P^0_B = 600 .....(ii) $$
If moles of A ^b initially are C & Y then
$$ X = 0.75 \times \frac {2}{3} (x +y) + 0.30 \times \frac {1}{3}( x +y)......(iii) $$
$$ x_A = \frac {X}{x +y} \quad or \quad x_B = \frac {y}{x +y} ......(iv) $$
solving gives
$$X_A = 0.6 \quad x_B = 0.4 , P^0_A = \frac { 2500}{3} torr $$ & $$ P^0_B = 500 torr $$
For ideal binary solution
$$p=x_{A}.p_{A}^{0}+x_{B}.p_{B}^{0}$$
This equation reflects
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Boyle's law
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Charles's law
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Dalton's law of partial pressure
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none of these
The reading of pressure gauge at which only liquid phase exists
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499
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399
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299
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none
Explanation
$$ X_A = \dfrac34=0.75; \quad X_B = 0.25 $$
$$ P_{\text{bubble point}} = X_A P^0_A + X_B P^0_B $$
$$ P_{\text{bubble point}} = X_A P^0_A + X_B P^0_B $$
$$ 0.75 +400 + 0.25 \times 800 = 500 mm $$
Above 500 mm Hg only liquid phase exists.
$$ y_A = 0.75; \quad \quad y_B = 0.5 $$
At dew point:
$$ \dfrac {1}{P_T } = \dfrac {Y_A }{P^0A} + \dfrac {Y_B}{P^0_B } \Rightarrow \dfrac {1}{ P_T} = \dfrac { 0.75}{400} + \dfrac { 0.25}{800} = \dfrac { 1.5 + 0.25}{800} $$
$$ \Rightarrow P_T = \dfrac {800}{1.75} = 457.14\ mm Hg $$
Below the dew point, only the vapour phase exists.
Which of the following solution in water possesses the lowest vapour pressure?
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$$0.1 (M) NaCl$$
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$$0.1 (M) BaCl_2$$
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$$0.1 (M) KCl$$
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None of these
Explanation
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
$$60 \,gm$$ of Urea (Mol. wt 60) was dissolved in $$9.9$$ moles of water. If the vapour pressure of pure water is $$P_0$$ , the vapour pressure of solution is
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$$0.10 \,P_0$$
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$$1.10 \,P_0$$
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$$0.90 \,P_0$$
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$$0.99 \,P_0$$
Explanation
Given that,
Moles of water. $$N=9.9$$ moles
Moles of urea, $$n=\dfrac{w}{M}=\dfrac{60}{60}=1$$
Now,
$$\dfrac {P^{0} - P_{S}}{P^{0}} = \dfrac {n}{N} \Rightarrow \dfrac {P^{0} - P_{S}}{P^{0}} = \dfrac {1}{9.9} \Rightarrow 9.9 \,P^{0} - 9.9 \,P_s = P^{0}$$
$$\Rightarrow 8.9 \,P^{0} = 9.9 \,P_s \Rightarrow P_s = \dfrac {8.9}{9.9} P^{0} \approx 0.90 \,P^{0}$$
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 $$23.8 \,mm \,Hg$$
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$$1.25 \,mm \,Hg$$
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$$0.125 \,mm \,Hg$$
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$$1.15 \,mm \,Hg$$
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$$00.12 \,mm \,Hg$$
Explanation
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
$$\dfrac {\Delta P}{P^{0}} = \dfrac {n}{n + N} \Rightarrow \dfrac {\Delta P}{23.8} = \dfrac {0.292}{0.292 + 55.5}$$
$$\Delta P = \dfrac {23.8 \times 0.292}{55.792} = 0.125 \,mm \,Hg$$
$$5 \,cm^3$$ of acetone is added to $$100 \,cm^3$$ of water, the vapour pressure of water over the solution
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It will be equal to the vapour pressure of pure water
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It will be less than the vapour pressure of pure water
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It will be greater than the vapour pressure of pure water
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It will be very large
Explanation
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.
According to kinetic theory of gases, the energy per mole of a gas is equal to
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$$1.5RT$$
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$$RT$$
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$$0.5RT$$
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$$2.5RT$$
Explanation
According to kinetic theory of gases, the energy per mole of a gas is equal to
$$1.5RT$$.
Hence, Option "A" is the correct answer.
The pressure P of a gas is plotted against its absolute temperature $$T$$ for two different constant volumes, $$V_{1}$$ and $$V_{2}$$. when $$V_{1}$$ > $$V_{2}$$, the:
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Curves have the same slope and do not intersect
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Curves must intersect at some point other than $$T = 0$$
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Curve for $$V_{2}$$ has a greater slope than that for $$V_{1}$$
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Curve for $$V_{1}$$ has a greater slope than that for $$V_{2}$$
Explanation
At constant volumes $$P \alpha T$$
$$P=$$ constant $$T; PV = nRT \because P= \dfrac {nR} {V} T$$
slope $$= m = \dfrac{nR}{V} \because V_{2} < V_{1}$$
$$\dfrac{m_{1}} {m_{2}} = \dfrac{V_{2}} {V_{1}} \because m_{1} < m_{2}$$ is curve for $$V.$$ has a greater slope than for $$V.$$
Which has maximum vapour pressure?
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$$HI$$
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$$HBr$$
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$$HCl$$
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$$HF$$
Explanation
The lower is boiling point more is the vapour pressure. Boiling point order is $$HCl < HBr < HI < HF$$
All kinds of matter:
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occupy space and have a definite mass
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have mass and a definite shape
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can change their states
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have a definite volume
Explanation
All kinds of matter occupy some space and they have a definite mass.
Option A is correct.
Solids and liquids are considered phases of matter.
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True
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False
Explanation
$$\text{Given statement is }True.$$
$$\text{Solids and liquids are considered phases of matter. these are the fundamental phases of matter including gas}$$ $$\text{(vapour), and others are considered to exist, including crystalline, colloid, glassy, amorphous, and}$$
$$\text{plasma phases.}$$
$$\text{Option A is correct}$$
Two which of the following the Dalton's law of particle pressure is not applicable?
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$$H_2$$ and $$He$$
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$$NH_3$$ and $$HCl$$
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$$N_2$$ and $$H_2$$
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$$N_2$$ and $$O_2$$
Explanation
Dalton's law of partial pressure is applicable to non-reaction gases $$NH_3$$ and $$HCl$$ are reacting gases, so Dalton's law will not be applicable for them.
Which of the following is not a colligative property?
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Vapour pressure
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Depression in f. pt.
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Elevation in b. pt.
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Osmotic pressure
Explanation
$$\text { Auswer:- (a) vapour pressure. }$$
Colligative properties are those properties of solutions that depend on the
ratio of number of solute particles to number of solvent particles in a solution.
There are 4 colligative properties:-
-vapour pressure Lowering
-osmotic pressure
-freezing point depression
-boiling point elevation
Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice:
Assertion: The vapour pressure of an aqueous solution is less than 1.013 bar at 373.15 K.
Reason: Vapour pressure of water is 1.013 bar at 373.15K.
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If both assertion and reason are true and reason is the correct explanation of assertion.
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If both assertion and reason are true but reason is not the correct explanation of assertion
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If assertion is true but reason is false.
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If both assertion and reason are false.
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Practice Class 11 Medical Chemistry Quiz Questions and Answers
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