CBSE Questions for Class 12 Engineering Chemistry Solutions Quiz 11 - MCQExams.com

Vapour Pressure of a mixture of benzene and toluene is given by $$P= 179X_{B} + 92$$, Where $$X_{B}$$ is mole fraction of benzene.
This condensed liquid again brought to the same temperature then what will be the mole fraction of benzene in vapour phase :
  • 0.007
  • 0.93
  • 0.65
  • 4.5
In three beakers labeled as (A), (B) and (C), $$100mL$$ of water, $$100mL$$ of $$1M$$ solution of glucose in water and $$100mL$$ of $$0.5M$$ solution of glucose in water are taken respectively and kept at same temperature.
Which of the following statements is correct?
  • Vapour pressure in all the three beakers is same
  • Vapour pressure of beaker B is highest
  • Vapour pressure of beaker C is highest
  • Vapour pressure of beaker B is lower than that of C and vapour pressure of beaker C is lower than that of A
For an ideal solution with $${p}_{A}^o>{p}_{B}^o$$, which of the following is true?
  • $${ \left( { x }_{ A } \right) }_{ liquid }={ \left( { x }_{ A } \right) }_{ vapour }$$
  • $${ \left( { x }_{ A } \right) }_{ liquid }> { \left( { x }_{ A } \right) }_{ vapour }$$
  • $${ \left( { x }_{ A } \right) }_{ liquid }< { \left( { x }_{ A } \right) }_{ vapour }$$
  • $${ \left( { x }_{ A } \right) }_{ liquid }$$ and $${ \left( { x }_{ A } \right) }_{ vapour }$$ cannot be correlated with each other.
Vapour pressure of pure water at $$298K$$ is $$23.8\ mm$$ $$Hg$$. $$50\ g$$ of urea is dissolved in $$850\ g$$ of water. The vapour pressure of water for this solution and its relative lowering are respectively:
  • $$23.8\ mm$$ $$Hg$$ and$$0.16$$
  • $$25.4\ mm$$ $$Hg$$ and $$0.02$$
  • $$30.2\ mm$$ $$Hg$$ and$$0.020$$
  • $$23.4\ mm$$ $$Hg$$ and $$0.017$$
If $$P_o$$ and $$P_s$$ are the vapour pressure of solvent and its solution respectively. $$x_1$$ and $$x_2$$ are the mole fraction of solvent and solute respectively then:
  • $$P_s = \dfrac{P_o}{x_2}$$
  • $$P_o - P_s = P_ox_2$$
  • $$P_s = P_ox_2$$
  • $$\dfrac{(P_o-P_s)}{P_s} = \dfrac{x_1}{(x_1+x_2)}$$
Two beakers of capacity $$500mL$$ were taken. One of these beakers, labelled as "A", was filled with $$400mL$$ water whereas the beaker labelled "B" was filled with $$400mL$$ of $$2M$$ solution of $$NaCl$$. At the same temperature, both the beakers were placed in closed containers of the same material and same capacity as shown in the figure.

At a given temperature, which of the following statements is correct about the vapour pressure of pure water and that of $$NaCl$$ solution?
933433_f283d5e5954941c1812dd8e7e3090553.png
  • Vapour pressure in container (A) is more than that in container (B)
  • Vapour pressure in container (A) is less than that in container (B)
  • Vapour pressure is equal to both the containers
  • Vapour pressure in container (B) is twice the vapour pressure in container (A)
Liquid $$A$$ and $$B$$ form ideal solution at temperature $$T$$. Mole fraction of $$A$$ in liquid and vapor phase are $$0.4$$ and $$4/3$$ respectively when total pressure is $$130$$ torr. The vapor pressure (in torr) of $$A$$ and $$B$$ in pure state at temperature $$T$$ are respectively.
  • $$100, 200$$
  • $$200, 100$$
  • $$100, 150$$
  • $$150, 100$$
Benzene and naphthalene form an ideal solution at room temperature. For this process, the true statements are:
(i) $$\Delta G$$ is positive  (ii) $$\Delta {S}_{system}$$ is positive
(iii) $$\Delta {S}_{surroundings}=0$$   (iv) $$\Delta H=0$$
  • (ii) and (iv) only
  • (i) and (iii) only
  • (ii), (iii) and (iv) only
  • all of these
In three beakers labelled as (A), (B) and ($$0.100$$ mL of water. $$100 mL$$ of $$1 M$$ solution of glucose in water and $$100$$ mL of $$0.5$$ M solution of glucose in water are, taken respectively and kept at the same temperature.
Which of the following statement is correct?
  • Vapour pressure in all the three beakers is same
  • Vapour pressure of beakers B is highest
  • Vapour pressure of beakers C is highest
  • Vapour pressure of beakers B is lower than that of C and vapour pressure of beaker C is lower than that is A
Which of the following is a property of an ideal solution?
  • It obeys Raoult's law
  • $$ \Delta \mathrm{H}_{\text {mixing }} =0$$
  • $$ \Delta V_{\text {mixing }}=0$$
  • All of these
Two liquids $$A$$ and $$B$$ form ideal solutions. At $$300\ K$$, the vapour pressure of a solution containing $$1$$ mole of $$A$$ and $$3$$ moles of $$B$$ is $$550\ mm$$ $$Hg$$. At the same temperature, if one more mole of $$B$$ is added to this solution, the vapour pressure of the solution increases by $$10\ mm$$ $$Hg$$. The vapour pressure of $$A$$ and $$B$$ in their pure states are respectively:
  • $${ p }_{ A }^{ o }=600\ mm$$ $$Hg$$ and $${ p }_{ B }^{ o }=400\ mm$$ $$Hg$$
  • $${ p }_{ A }^{ o }=500\ mm$$ $$Hg$$ and $${ p }_{ B }^{ o }=560\ mm$$ $$Hg$$
  • $${ p }_{ A }^{ o }=450\ mm$$ $$Hg$$ and $${ p }_{ B }^{ o }=650\ mm$$ $$Hg$$
  • $${ p }_{ A }^{ o }=400\ mm$$ $$Hg$$ and $${ p }_{ B }^{ o }=600\ mm$$ $$Hg$$
The vapour pressure of ethanol and methanol are $$44.5\ mm$$ $$Hg$$ and $$88.7\ mm$$ $$Hg$$ respectively. An ideal solution is formed at the same temperature by mixing $$60\ g$$ of ethanol with $$40\ g$$ of methanol. The total vapour pressure of the solution and the mole fraction of methanol in the vapour are respectively:
  • $$43.46\ mm$$ and $$0.51$$
  • $$66.13\ mm$$ and $$0.657$$
  • $$66.15\ mm$$ and $$0.791$$
  • $$70.59\ mm$$ and $$0.657$$
What will be the degree of dissociation of $$0.1M$$ $$Mg{({NO}_{3})}_{2}$$ solution if van't Hoff factor is $$2.74$$?
  • $$75$$%
  • $$87$$%
  • $$100$$%
  • $$92$$%
When a non volatile solute is added to a pure solvent, the :
  • vapour pressure of the solution becomes lower then that of the pure solvent
  • rate of evaporation of the pure solvent is reduced
  • solute does not effect the rate of condensation
  • rate of the evaporation of the solution is equal to the rate of condensation of the solution at a lower vapour pressure than that in the case of the pure solvent
What is the composition of last deoplet of liquid remaining in equilibrium with vapour?
  • $$x_A = 0.6; x_B = 0.4$$
  • $$x_A = 0.5; x_B = 0.5$$
  • $$x_A = 0.7; x_B = 0.3$$
  • $$x_A = 0.3; x_B = 0.7$$
The amount of glucose to be dissolved in 500 g of water so as to produce the same lowering in vapour pressure as that of 0.2 molal aqueous urea solution is:
  • 9 g
  • 18 g
  • 36 g
  • 1.8 g
Vapour pressure of a pure liquid $$X$$ is $$2$$ atm at $$300$$K. It is lowered to $$1$$ atm on dissolving $$1$$g of $$Y$$ in $$20$$g of liquid $$X$$. If molar mass of $$X$$ is $$200$$, what is the molar mass of $$Y$$?
  • $$20$$
  • $$10$$
  • $$100$$
  • $$30$$
Two liquids X and Y form an ideal solution.
The mixture has a vapour pressure of 400mm at 300K, when mixed in the molar ratio of 1:1 and a vapour pressure of 350mm when mixed in the molar ratio of 1:2 at the same temperature. The vapour pressures of the two pure liquids X and Y respectively are?
  • 250mm, 550mm
  • 350mm, 450mm
  • 350mm, 700mm
  • 550mm, 250mm
Which among the following has lowest vapour pressure?
  • $$0.5M\ Al_{2}(SO_{4})_{3}$$
  • $$12\%$$ Urea solution
  • $$1M\ NaCl(aq)$$
  • $$18\%$$ Glucose solution
Vapour pressure of a saturated solution of a sparingly soluble salt $$A_2B_3$$ is 31.8 mm of Hg at $$40^{\circ}C$$. If vapour pressure of pure water is 31.8 mm of Hg at $$40^{\circ}C$$ the solubility product of $$A_2B_3$$ at $$40^{\circ}C$$ is:
  • $$5.67\times 10^{-6}$$
  • $$1.42\times 10^{-6}$$
  • $$6.30\times 10^{-5}$$
  • 1
For the two compounds, the vapour pressure of (2) at a particular temperature is expected to be:-
1070517_78a30913154143e5bb45bbc66e4cf859.PNG
  • Higher than (i)
  • Lower than that of (i)
  • Same as that of (i)
  • Can be 'higher or lower depending upon the size of the vessel
$$100\space g$$ of liquid $$A$$(molar mass $$140\space g { mol }^{ -1 })$$ was dissolved in $$1000\space g$$ of liquid $$B$$ (molar mass $$180 \space g { mol }^{ -1 })$$. The vapour pressure of pure liquid $$B$$ was found to be $$500 \space torr.$$ Calculate the vapour of pure liquid $$A$$ and its vapour pressure in the solution if the total vapour pressure of the solution is $$475 \space torr$$.
  • $$22\space torr$$
  • $$32\space torr$$
  • $$45 \space torr$$
  • $$36 \space torr$$
Which of the following colligative property is useful to determine molecular masses of polymer compounds from their solutions?
  • Decrease in vapour pressure
  • Elevation in boiling point
  • Depression in freezing point
  • Osmotic pressure

$$18.0\ g$$ of glucose$$\left( {{C_6}{H_{12}}{O_6}} \right)$$ is added to $$178.2\ g$$ of water. The vapour pressure of water for this aqueous solution at $${100^o}\ C$$ is :
  • $$759..00$$ Torr
  • $$7.60$$ Torr
  • $$76.00$$ Torr
  • $$752.40$$ Torr
100 g of liquid $$A$$ (molar mass 140 g $$mol^{-1}$$) was dissolved in 1000 g of liquid $$B$$ (molar mass 180 g $$mol^{-1}$$) The vapour pressure of pure liquid $$B$$ was found to be 500 torr. 

Calculate the vapour pressure of pure liquid $$A$$ and its vapour pressure in the solution if the total vapour pressure of the solution is 475 torr:
  • $$3.19, 500$$
  • $$283.18, 31.999$$
  • $$500, 300$$
  • $$190, 31.965$$
Which of the following changes decreases the vapour pressure of water kept in a sealed vessel?
  • Decreasing the quantity of water
  • Increasing the quantity of water
  • Decreasing the volume of vessel to one-half
  • Decreasing the temperature of water
The vapour pressure of pure $$A$$ is 10 torr and at the same temperature when 1 g of $$B$$ is dissolved in 20 gm of $$A$$, its vapour pressure is reduced to 9.0 torn If the molecular mass of $$A$$ is 200 amu, then the molecular mass of $$B$$ is:
  • 100 amu
  • 90 amu
  • 75 amu
  • 120 amu
$${ \Delta  }_{ f }{ G }^{ }$$ at 500 K for substance $$S$$ in liquid state and gaseous state are +100.7 kcal $${ }^{ -1 }$$ and +103 kcal $${ }^{ -1 }$$, respectively. Vapour pressure of liquid $$S$$ at 500 K is approximately equal to:
($$R=2\ cal $$ $${ K }^{ -1 }{ }^{ -1 }$$)
  • 0.1 atm
  • 10 atm
  • 100 atm
  • 1 atm
Which of the following change is observed occurs when a substance X is converted from liquid to vapour phase at the standard boiling point?
I.Potential energy of the system decreases
II. The distance between molecules increases
III. The average kinetic energy of the molecules in both phases are equal.
  • I only
  • II only
  • III only
  • II and III only
In the given equilibrium, $${ H }_{ 2 }O(l)\rightleftharpoons { H }_{ 2 }O(g)$$ at $$100^oC$$ the vapour pressure is $$1 \ atm$$. If the volume of the container is halved, after sometime the vapour pressure becomes:
(assuming constant temperature)
  • $$1.5 atm$$
  • $$2.5 atm$$
  • $$2 atm$$
  • $$1 atm$$
The vapour pressure of a pure liquid $$A$$ is $$70$$ torr at $$27^oC$$. It forms an ideal solution with another liquid $$B$$. The mole fraction of $$B$$ is $$0.2$$ and total vapour pressure of the solution is $$84$$ torr at $$27^oC$$. The vapour pressure of pure liquid $$B$$ at $$27^o$$C is:
  • $$14$$
  • $$56$$
  • $$140$$
  • $$70$$
Which solution has the highest vapour pressure?
  • 0.02 M $$NaCl$$ at $$50^o C$$
  • 0.03 M sucrose at $$15^oC$$
  • 0.005 M $$CaCl_2$$ at $$50^oC$$
  • 0.005 M $$CaCl_2$$ at $$25^oC$$
Van't Hoff factor i is given by the expression:
  • $$i = \frac{Normal\ molar mass} {Abnormal\ molar mass}$$
  • $$i = \frac{Abnormal\ molar mass} {Normal\ molar mass} $$
  • $$ i = \frac{Observed\ colligative\ property} {Calculated\ colligative\ property}$$
  • $$ i = \frac {Calculated\ colligative\ property} {Observed\ colligative\ property}$$
On increasing temperature, vapour pressure of a substance
  • always increases.
  • decreases.
  • does not depend on temperature.
  • partially depends on temperature.
Which of the following is not a colligative property?
  • Vapour pressure
  • Depression in f. pt.
  • Elevation in b. pt.
  • Osmotic pressure
At $$20^{o}C$$, the vapour pressure of $$0.1\ M$$ solution of urea is $$0.0311\ mm$$ less than that of water and the vapour pressure of $$0.1\ M$$ solution of $$KCl$$ is $$0.0574\ mm$$ less than that of water. The apparent degree of dissociation of $$KCl$$ at this dilution is :
  • $$92.1\%$$
  • $$84.6\%$$
  • $$68.4\%$$
  • $$54.1\%$$
Reaction of $${NO}$$ takes place with hydrogen if equal molar mixture of snow and hydrogen is taken at initial total pressure of 350 mm of Mercury, total pressure reduces to half its value after 121 seconds while if initial total pressure would have been 275 mm it reduces to half of the 196 seconds calculate the order of reaction?
  • 0
  • 1
  • 2
  • 3
The brown gas Y in the mixture is?
  • Nitric oxide
  • Nitrous oxide
  • Dinitrogen tetroxide
  • Nitrogen dioxide
If $${ CuSO }_{ 4 }\cdot 5H_{ 2 }O\left( s \right) \rightleftharpoons { CuSO }_{ 4 }\cdot { 3H }_{ 2 }O\ (s)+{ 2H }_{ 2 }O\ (l){ K }_{ p }=1.086\times { 10 }^{ -4 }{ atm }^{ 2 }\ at\ { 25 }^{ o }C$$ The efflorescent nature of $${CuSO}_{4}\cdot \ {5H}_{2}O$$ can be noticed when vapour pressure of $$ {H}_{2}O$$ in atmosphere is:
  • $$>7.92\ mm$$
  • $$<7.92\ mm$$
  • $$\gtrless7.92\ mm$$
  • none of these
A solution of a non-volatile solute in water has a boiling point of 375.3K. Calculate the vapour pressure of water above this solution at 338K. Given, Po (water) = 0.2467 atm at 338K and Kb for water = 0.52.
  • $$0.18\ atm$$
  • $$0.23\ atm$$
  • $$0.34\ atm$$
  • $$0.925\ atm$$
Which of the following has least vapour presure ?
  • $$0.1\ M\ NaCl$$
  • $$0.1\ M\ MgCl_{2}$$
  • $$0.1\ M\ AlCl_{3}$$
  • $$0.1\ M\ K_4[Fe(CN)_{6}]$$
The empirical formula of a  monobasic acid is $${CH}_{2}O$$. The vapour density of its ethyl ester is $$44$$. What is the Molecular formula of the acid?
  • $${C}_{2}{H}_{4}{O}_{2}$$
  • $${CH}_{2}{O}_{2}$$
  • $${C}_{2}{H}_{2}{O}_{2}$$
  • $${C}_{3}{H}_{6}{O}_{3}$$
Moles of $$Na_2SO_4$$ to be dissolved in 12 mole of water to lower its vapour pressure by 10 millimeter Mercury at a temperature at which vapour pressure of pure water is 50 millimeters?
  • 1.5 moles
  • 2 moles
  • 1 mole
  • 3 moles
The solubility product  of $$ A{s_2}{O_3}$$ is $$10.8 \times {10^{ - 9}}$$. It is $$50\%$$ dissociated in saturated solution. The solubility of salt is : 
  • $${10^{ - 2}}$$
  • $$2 \times {10^{ - 2}}$$
  • $$5 \times {10^{ - 3}}$$
  • $$5.4 \times {10^{ - 9}}$$
$$90 gm$$ of glucose is dissolved in $$45 g$$ of water at $$350K$$. If vapor pressure of pure water at $$350 K$$ is $$600mm$$ of $$Hg$$. Then vapor pressure of solution. (in $$mm$$ of $$Hg$$)
  • $$500$$
  • $$100$$
  • $$400$$
  • $$300$$
A spherical balloon of $$21\ cm$$ diameter is to be filled up with $$H_2$$ at $$NTP$$ from a cylinder containing the gas at $$20\ atm$$ at $$27^{\circ}C$$. The cylinder can hold $$2.82$$ litre of water. The number of balloons that can be filled up
  • 11
  • 10
  • 8
  • 1
The vapour pressure of a given liquid will decrease if:
  • surface area of liquid will decreased
  • the volume of liquid in the container is decreased
  • the volume of the vapour phase is increased
  • the temperature is decreased
An aqueous solution containing liquid $$A(M.\ wt.\ =128)\ 64\%$$ by weight has a vapour pressure of $$145\ mm\ Hg$$. If the vapour pressure of water is $$155\ mm\ Hg$$ then vapour of $$A$$ at the same temperature will be
  • $$205\ mm\ Hg$$
  • $$105\ mm\ Hg$$
  • $$185\ mm\ Hg$$
  • $$52.5\ mm\ Hg$$
The solubility of a specific non-volatile salt is 4g in 100 g of water at $${25}^{0}$$C. If 2.0g, 4.0g and 6.0g of the salt added of 100g of water at $${25}^{0}$$C, in system X, Y and Z. The vapour pressure would be in the order:
  • $$Z>Y>X$$
  • $$X>Y>Z$$
  • $$Z>X=Y$$
  • $$X>Y=Z$$
The pressure exerted by a mass of x mg resting on the area of 1.00 $${ cm }^{ 2 }$$ is 1.00 Pa, then x is
  • 10.6
  • 10.3
  • 103
  • 10.2
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