CBSE Questions for Class 12 Engineering Chemistry Solutions Quiz 6 - MCQExams.com

$$3$$ moles of $$P$$ and $$2$$ moles of $$Q$$ are mixed, what will be their total vapour pressure in the solution if their partial vapour pressures are $$80$$ and $$60$$ torr respectively?
  • $$80$$ torr
  • $$140$$ torr
  • $$72$$ torr
  • $$70$$ torr
Van't-Hoff factor(i) for this reaction is:
995502_aa4a7d1a4f794ed4af80ae7936176e23.png
  • $$2$$
  • $$3$$
  • $$4$$
  • $$5$$
What is the value of Van't-Hoff factor $$i$$ for $$0.1\,m$$ ideal solution?
  • $$1$$
  • $$0$$
  • $$0.1$$
  • $$0.01$$
On dissolving sugar in water at room temperature solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid?
  • Sugar crystals in cold water
  • Sugar crystals in hot water
  • Powdered sugar in cold water
  • Powdered sugar in hot water
The value of van't Hoff factors for $$KCl, NaCl$$ and $${K}_{2}{SO}_{4}$$, respectively, are :
  • $$2, \ 2$$ and $$2$$
  • $$2, \ 2$$, and $$3$$
  • $$1, \ 1$$ and $$2$$
  • $$1, \ 1$$ and $$1$$
What will be the abnormal molecular mass of $${{\text{K}}_3}\left[ {{\text{Fe}}{{\left( {{\text{CN}}} \right)}_6}} \right]$$. If in a aqueous solution it is 40% dissociated? (Given, normal molecular weight of $${{\text{K}}_3}\left[ {{\text{Fe}}{{\left( {{\text{CN}}} \right)}_6}} \right]$$ is 329)
  • $$149.54$$
  • $$723.8$$
  • $$82.25$$
  • $$329.0$$
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.
  • $${i}_{A}< {i}_{B}< {i}_{C}$$
  • $${i}_{A}> {i}_{B}> {i}_{C}$$
  • $${i}_{A}= {i}_{B}= {i}_{C}$$
  • $${i}_{A}< {i}_{B}> {i}_{C}$$
The boiling point of liquid A, B, C and D are $$80{\,^o}C,\,\,60{\,^o}C,\,90{\,^o}C$$ and $$100{\,^o}C$$ respectively. Which will show highest vapour pressure at room temperature?
  • A
  • B
  • C
  • D
Let $$P_s$$ and $$P$$ be the saturated partial pressure and partial pressure of water respectively, then the relative humidity is given by:
  • $$\dfrac{P_s+P}{P_s}\times 100$$
  • $$\dfrac{P}{P_s}\times 100$$
  • $$\dfrac{P_s}{P}\times 100$$
  • $$(P+P_s)\times 100$$
The vapour pressure of a solvent at $$293$$K is $$100$$ mm Hg. Then the vapour pressure of a solution containing $$1$$ mole of a strong electrolyte $$(AB_2)$$ in $$99$$ moles of the solvent at $$293$$ K is:
(Assume complete dissociation of solute)
  • $$103$$ mm Hg
  • $$99$$ mm Hg
  • $$97$$ mm Hg
  • $$101$$ mm Hg
Which of the following has maximum vapour pressure at a given temperature?

Calculate Vant Hoff factor (i) of the compound acetic acid in benzene if their $$\alpha=50$$%.
  • $$0.25$$
  • $$1.5$$
  • $$0.75$$
  • $$2$$
Two liquids X and Y form an ideal solution. At $$300$$K, vapour pressure of the solution containing $$1$$ mol of X and $$3$$ mol of Y is $$550$$ mm Hg. At the same temperature, if $$1$$ mol of Y is further added to this solution, vapour pressure of the solution increases by $$10$$ mmHg. Vapour pressure (in mm Hg) of X and Y in their pure states will be ________ respectively.
  • $$200$$ and $$300$$
  • $$300$$ and $$400$$
  • $$400$$ and $$600$$
  • $$500$$ and $$600$$
A solution at $$20^o$$C is composed of $$1.5$$ mol of benzene and $$3.5$$ mol of toluene. If the vapour pressure of pure benzene of pure benzene and pure toluene at this temperature are $$74.7$$ torr and $$22.3$$ torr. respectively, then the total vapour pressure of the solution and the benzene mole fraction in equilibrium with it will be, respectively.
  • $$38.0$$ torr and $$0.589$$
  • $$30.5$$ torr and $$0.389$$
  • $$35.8$$ torr and $$0.280$$
  • $$35.0$$ torr and $$0.480$$
At what relative humidity will $$Na_2SO_4$$ be deliquescent (absorb moisture) when exposed to the air at $$0^o$$C? 
Given: $$Na_2SO_4\cdot 10H_2O(s)\rightleftharpoons Na_2SO_4(s)+10H_2O(g); K_p=4.08\times 10^{-25}$$ and vapour pressure of water $$0^o$$C $$=4.58$$ Torr.
  • Below $$50.5\%$$ but Above $$30.5\%$$
  • Above $$50.5\%$$ 
  • Above $$30.5\%$$
  • Below $$30.5\%$$
An ideal solution has equal mol-fractions of two volatile components A and B in the vapour above the solution, the mol-fractions of A and B.
  • are both $$0.50$$
  • are equal but necessarily $$0.50$$
  • are not very likely to be equal
  • are $$1.00$$ and $$0.00$$ respectively
What is the density of wet air with $$75\%$$ relative humidity at $$1$$ atm and $$300$$ K? 
[Given: vapour pressure of $$H_2O$$ is $$30$$ torr and average molar mass of air is $$29$$g $$mol^{-1}$$]
  • $$1.614$$ g/L
  • $$0.96$$ g/L
  • $$1.06$$ g/L
  • $$1.164$$ g/L
Phenol-water system is a/an __________.
  • element
  • compound
  • homogeneous system
  • heterogeneous system
A binary liquid solution of n-heptane and ethyl alcohol is prepared. Which of the following statements correctly represents the behaviour of this liquid solution?
  • The solution formed is an ideal solution
  • The solution formed is a non-ideal solution with positive deviations from Raoult's law
  • The solution formed is non-ideal solution with negative deviations from Raoult's law
  • Normal-heptane exhibits positive deviations, whereas ethyl alcohol exhibits negative deviations from Raoult's law
The vapour pressure of two pure liquids $$(A)$$ and $$(B)$$ are $$100$$ and $$80\ torr$$ respectively. The total vapour pressure of solution obtained by mixing $$2$$ moles of $$(A)$$ and $$3$$ moles of $$(B)$$ would be :-
  • $$120\ torr$$
  • $$36\ torr$$
  • $$88\ torr$$
  • $$180\ torr$$
The vapour pressure of two liquids $$P$$ and $$Q$$ are $$80$$ torr and $$60$$ torr respectively. The total vapour pressure obtained by mixing $$3$$ mole of P and $$2$$ mole of $$Q$$ would be:
  • $$68$$ torr
  • $$20$$ torr
  • $$140$$ torr
  • $$72$$ torr
The relative lowering of the vapour pressure of an aqueous solution containing a non volatile solute is $$0.0125$$. The molality of the solution is:
  • $$0.70$$
  • $$0.50$$
  • $$0.80$$
  • $$0.40$$
A substance is completely trimerized on dissolution in a solvent. The Van't Hoff factor ($$i$$) for such change is:
  • $$1$$
  • $$2$$
  • $$3$$
  • $$1/3$$

What will b the result if $$100ml{\text{ of }}0.06{\text{ M }}Mg{\left( {N{O_3}} \right)_2}$$  is added to $$50ml{\text{ of 0}}{\text{.06M }}N{a_2}{C_2}{O_4}?$$ $$\left[ {{K_{sp}}{\text{ of }}Mg{C_2}{O_4} = 8.6{\text{ x }}{{10}^{ - 5}}} \right]$$
  • A precipitate will not be formed
  • A precipitate will form and an excess of $$Mg{^{2 + }}$$ ions will remain in the solution
  • A precipitate will form and an excess of $${C_2}{O_4}^{2 - }$$ ions will remain in the solution
  • A precipitate is form but neither ion is present in excess
What would be the vapour pressure of 0.5 molal solution of non volatile solute in benzene at $$30^oC$$ ? The vapour pressure of pure benzene at $$30^oC$$ is 119.6 torr.
  • 119.6 torr
  • 121.23 torr
  • 118.52 torr
  • None of these
If 2 moles of A and 3 moles of B are mixed to form an ideal solution vapour pressure of A and B are 120 and 180 mm of Hg respectively. then the composition of A and B in the Vapour phase when the first traces of vapour are formed in the above case is:
  • $$X^l A = 0.407$$
  • $$X^l A = 0.8$$
  • $$X^l A = 0.109$$
  • $$X^l A = 0.307$$
The vapour pressure of a pure liquid A is $$70$$ torr at $$27^o$$C. 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 $$27^o$$C. The vapour pressure of pure liquid B at $$27^o$$C.
  • $$14$$
  • $$56$$
  • $$140$$
  • $$70$$
The vapour pressure of pure water is 760 mm at $$25^{ 0 }C$$.The vapour pressure of solution containing 1(m) solution of glucose will be:
  • 761.0 mm
  • 746.5 mm
  • 734.5 atm
  • 746.5 Pa
The van't Hoff factor is 3 for:
  • $$Na_2SO_4$$ with 50% dissociation
  • $$Al_2(SO_4)_3$$
  • $$CaCl_2$$ with 80% dissociation
  • $$K_4[Fe(CN)_6]$$ with 50 % dissociation
A Solution of non-volatile solute in water freezes at $$-0.{ 30 }^{ }C.$$ The vapour-pressure of pure water at $$298K$$ is $$23.51mm Hg$$ and $${ K }_{ 1 }$$ for water is $$1.86 K. kg { mol }^{ -1 }$$ Calculate the vapour-pressure of this solution at $$298K.$$
  • $$23.4mm$$
  • $$24.8mm$$
  • $$34.8mm$$
  • $$40mm$$
The composition of vapour when first bubble formed is:
  • $$y_A = 0.6; y_B = 0.4$$
  • $$y_A = 0.48; y_B = 0.52$$
  • $$y_A = 0.52; y_B = 0.48$$
  • $$y_A = 0.5; y_B = 0.5$$
The vapour pressure of water at $$20^{o}C$$ is $$17.54mm Hg$$. Then the vapour pressure of the water in the apparatus is lowered, decreasing the volume of the gas above the liquid to one half of its initial volume (temp. constant) is:
  • $$5.77\ mmHg$$
  • $$16\ mmHg$$
  • $$35.08\ mmHg$$
  • between $$8.77$$ and $$15.54\ mmHg$$
A liquid A and B form an ideal solution. If vapour pressure of pure A and B are $$500N{ m }^{ -2 }$$ and $$200N{ m }^{ -2 }$$ respectively, the vapour pressure of a solution of A and B containing 0.2 mole fraction of A would be:
  • $$700N{ m }^{ -2 }$$
  • $$300N{ m }^{ -2 }$$
  • $$260N{ m }^{ -2 }$$
  • $$140N{ m }^{ -2 }$$
A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of $$290\ mm$$ at $$300\ K$$. The vapour pressure of propyl alcohol is $$200\ mm$$. If the mole fraction of ethyl alcohol is $$0.6$$, its vapour pressure (in $$mm$$) at the same temperature will be:
  • $$300$$
  • $$700$$
  • $$360$$
  • $$350$$
A $$3.00\ L$$ oxygen gas is collected over water at $${27}^{o}C$$ when the barometric pressure is $$787\ Torr$$. If vapour pressure of water is $$27\ Torr$$ at $${27}^{o}C$$, moles of $$O_{2}$$ gas will be?
  • $$0.122$$
  • $$0.126$$
  • $$0.004$$
  • $$0.152$$
Which of the following condition is not followed for an ideal solution?
  • $$\Delta { H }_{ mixing }$$=0
  • $$\Delta { S }_{ mixing }$$=0
  • $$\Delta { v }_{ mixing }$$=0
  • All A, B, and C are followed
Which of the following pair will form an ideal solution?
  • Chlorobenzen , chloro ethane
  • Benzene, Toluene
  • Acetone, chloroform
  • Water, HCl
$$3$$ moles of $$P$$ and $$2$$ moles of $$Q$$ are mixed, what will be their total vapour pressure in the solution if their partial vapour pressures are $$80$$ and $$60$$ respectively?
  • $$80$$ torr
  • $$140$$ torr
  • $$720$$ torr
  • $$70$$ torr
For which of the following binary solution $${P}_{Total}={P}_{A}^{o}\times {X}_{A}+ {P}_{B}^{o}\times {X}_{B}$$ is followed?
  • Phenol+ Aniline
  • Benzene + Toluene
  • Acetone + Chloroform
  • water + $$HCl$$
How many grams of sucrose must be added to $$320g$$ of water to lower the vapour pressure by $$1.5mm$$ $$Hg$$ at $${25}^{o}C$$?
(Given: The vapour pressure of water at $${25}^{o}C$$ is $$23.8mm$$ $$Hg$$ and molar mass of sucrose is $$324.3g/mol$$)
  • $$21.5g$$
  • $$140g$$
  • $$363.36g$$
  • $$160.12g$$
If two liquids $$A({P}_{A}^{o}=100torr)$$ and $$B({P}_{B}^{o}=200torr)$$ are completely immiscible with each other, each one will behave independently of the other are present in closed vessel. The total pressure of the system will be:
  • less than $$100 $$torr
  • less than $$200 $$torr
  • between $$100$$ and $$200$$ torr
  • $$300$$ torr
If $$P^{0}_{A}$$ and $$P^{0}_{B}$$ are $$108$$ and $$36$$ torr respectively. What will be the mole fraction of $$A$$ is vapour phase if $$B$$ has mole fraction in solution $$0.5$$:
  • $$0.25$$
  • $$0.75$$
  • $$0.60$$
  • $$0.35$$
The vapour pressure of a liquid decreases by $$10 torr$$ when a non-volatile solute is dissolved. The mole fraction of the solute in solution is $$0.1$$. What would be the mole fraction of the liquid if the decrease in vapour pressure is $$20torr$$, the same solute being dissolved?
  • $$0.2$$
  • $$0.9$$
  • $$0.8$$
  • $$0.6$$
A manometer attached to a flask containing  ammonia gas have no difference in mercury level initially as shown in diagram. After sparking into the flask, ammonia is partially dissociated as $${ 2NH }_{ 3 }(g)\longrightarrow N_{ 2 }(g){ +3H }_{ 2 }(g)$$ now it have difference of $$6\ cm$$ in mercury level in two columns, what is partial pressure of $${ H }_{ 2 }(g)$$ at equilibrium?
1076008_ab92dfd3146148508da94833427f1c7d.PNG
  • $$9\ cm\ Hg$$
  • $$18\ cm\ Hg$$
  • $$27\ cm\ Hg$$
  • $$None\ of\ these$$
If the relative lowering in vapour pressure for he ethanolic solution containing non volatile solute is $$0.02$$, then the molality of solution will be.(molecular mass of ethanol = $$46$$ gm/mole)
  • $$0.22 m$$
  • $$1.33 m$$
  • $$1.09 m$$
  • $$0.44 m$$
18 g glucose is added to 178.2 g of water the vapour pressure of water for this aqueous solution at $${ 100 }^{ 0 }C$$ is:
  • 704 torr
  • 759 torr
  • 7.6 torr
  • None of these
The mass of glucose that should be dissolved in $$100g$$ water in order to produce same lowering of vapour pressure as produced by dissolving $$1g$$ urea in $$50g$$ of water is?
  • $$1g$$
  • $$2g$$
  • $$6g$$
  • $$12g$$
The vapour pressure of o-nitrophenol at any given temperature is predicted to be: 
  • Higher than that of p-nitrophenol
  • Lower than that of p-nitrophenol
  • Same as that of p-nitrophenol
  • Higher or lower depending upon the size of the vessel
The vapour pressure is least for?
  • pure water
  • 0.1m aqueous urea
  • 0.2m aqueous urea
  • 0.3m aqueous urea
Relative lowering of vapour pressure is maximum for:
  • 0.1m urea
  • 0.1m NaCI
  • $$0.1m\quad Mg{ CI }_{ 2 }$$
  • $$0.1m\quad AI_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 }$$
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