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CBSE Questions for Class 12 Engineering Chemistry Solutions Quiz 7 - MCQExams.com
CBSE
Class 12 Engineering Chemistry
Solutions
Quiz 7
Two liquids A and B form an ideal solution. The vapour pressure of pure A and pure B are 66mm of Hg and 88mm of Hg, respectively. Calculate the composition of vapour A in the solution which is equilibrium and whose molar volume is 36%.
Report Question
0%
0.43
0%
0.70
0%
0.30
0%
0.50
Explanation
P
t
=
P
A
+
P
B
=
66
m
m
+
88
m
m
=
154
m
m
of
H
g
Now,
P
A
=
X
A
×
P
T
Therefore,
X
A
=
P
A
P
T
=
66
154
=
0.43
Therefore, composition of Vapour A is
0.43
.
Vapour pressure of
C
C
I
4
at
24
o
C
is
143
m
m
H
g
0.05
g of the non-volatile solute (mol.wt.=65) is dissolved in
100
m
l
C
C
I
4
. Find the vapour pressure of the solution (Density of
C
C
I
4
=
1.58
g
/
c
m
2
)
Report Question
0%
143.99
m
m
0%
94.39
m
m
0%
199.34
m
m
0%
14.197
m
m
Explanation
The equation of relative lowering vapour pressure is given as-
p
0
−
p
p
0
=
X
2
Whereas,
p
0
=
Vapour prssure of solvent
p
=
Vapour pressure of solution
X
2
=
Mole fraction of solute
Given that density of
C
C
l
4
is
1.58
g
/
c
m
3
As we know that,
density
=
mass
volume
⇒
1.58
=
mass
100
⇒
mass of
C
C
l
4
=
158
g
Molecular weight of
C
C
l
4
=
154
g
∴
No. of moles of
C{Cl}_{4} = \cfrac{158}{154} = 1.026 \text{ mol}
Given weight of solute
= 0.05 \; g
Molecular weight of solute
= 65 \; g
\therefore
No. of moles of solute
= \cfrac{0.05}{65} = 0.00077 \text{ mol}
\therefore
Total no. of moles
= 1.026 + 0.00077 = 1.02677 \text{ mol}
\therefore
Mole fraction of solute
= \cfrac{0.00077}{1.02677} = 0.00075
Vapour pressure of solvent
= 143 \text{ mm of Hg}
Noe from equation of relative lowering vapour pressure, we have
\cfrac{143 - p}{143} = 0.00075
\Rightarrow 143 - p = 0.107
\Rightarrow p = 142.893 \text{ mm of Hg}
Hence the vapour pressure of solution is
142.893 \text{ mm of Hg}
.
Which of the liquids in each of the following pairs has a higher vapour pressure?
Report Question
0%
Alcohol, glycerine
0%
Mercury, water
0%
petrol, kerosene
0%
None of these
Explanation
Alcohol and glycerine have high vapour pressure because they have high intermolecular attraction.
As the intermolecular attraction increases vapour pressure increases.
The vapour pressure of water at
20
is 17.5 mm Hg. If 18 g of glucose
{ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }
is added to 178.2 g water
20
, the vapour pressure of the resulting solution will be:
Report Question
0%
17.675 mm Hg
0%
15.750 mm Hg
0%
16.500 mm Hg
0%
17.325 mm Hg
Explanation
No. of moles of glucose=
\cfrac{18}{180}=0.1
No. of moles of water=
\cfrac{178.2}{18}=9.9
Mole fraction of glucose=
\cfrac{0.1}{4.9+0.1}=\cfrac{0.1}{10}=0.01
Using Raoult's law, as solute is non-volatile,
{ x }_{ \beta }=\cfrac { { P }_{ A }^{ o }-{ P }_{ A } }{ { P }_{ A }^{ o } }
P_{A}^{o}=
vapour pressure of pure water
P_{A}=
vapour pressure of the solution
x_{\beta}=
mole fraction of glucose
\Longrightarrow 0.01=\cfrac { 17.5-{ P }_{ A } }{ 17.5 } \\ \Longrightarrow { P }_{ A }=17.5-0.175=17.325
The vapor pressure of the mixture=17.325 mm Hg.
Hence, the correct option is
D
At
{ 20 }^{ 0 }C
, the vapour pressure of diethyl either is 44mm. When 6.4 g. of a non-volatile solute is dissolved in 50g. of either, the vapour pressure falls to 410mm. The Molecular weight of the solute is:
Report Question
0%
150
0%
130
0%
160
0%
180
Explanation
\Delta _{P}=440-410=30mm
\therefore \dfrac{\Delta _{P}}{P_{0}}=x_{solute}
\Rightarrow \displaystyle \frac{30}{440}=\frac{\frac{6.4}{M}}{\frac{6.4}{M}+\frac{50}{74}}
\Rightarrow \displaystyle \frac{19.2}{M}+\frac{150}{74}=\frac{44\times 6.4}{M}
\Rightarrow \displaystyle \frac{150}{74}=\frac{6.4(44-3)}{M}
\Rightarrow \displaystyle M=\frac{6.4\times 41\times 74}{150}
\approx 130
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
torr. If the molecular mass of
A
is
200
amu, then the molecular mass of
B
is:
Report Question
0%
100\ amu
0%
90\ amu
0%
75\ amu
0%
120\ amu
Explanation
According to Dalton's law of partial pressure,
p_{total}=\chi_Ap_A+\chi_Bp_B
Since B is a non-volatile substance,
p_B=0
\Rightarrow p_{total}=p_A\times \dfrac{\dfrac{m_A}{M_A}}{\dfrac{m_A}M_A+\dfrac{m_B}{M_B}}
\Rightarrow 9=10\times \dfrac{\dfrac{20}{200}}{\dfrac{20}{200}+\dfrac{1}{M_B}}
\Rightarrow M_B=90\ amu
Hence, option
B
is the correct answer.
The vapour pressure of a solvent decreased by 10 mm of mercury when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.What should be the mole fraction of the solvent if the decrease in the vapour pressure is to be 20 mm of mercury?
Report Question
0%
0.4
0%
0.6
0%
0.8
0%
0.2
Explanation
\cfrac {\Delta P}{P_o}=\cfrac {n}{n+N}
\Rightarrow \cfrac {10}{P_o}=0.2
\Rightarrow P_o=50mm
For other solutions of same solvent,
\Rightarrow \cfrac {20}{P_o}=\cfrac {n}{n+N}
\Rightarrow \cfrac {20}{50}=
mole fraction of solute=
0.4
\therefore
Mole fraction of solvent=
1-0.4=0.6
Hence, the correct option is
\text{B}
Vapours of a liquid can exist only at ?
Report Question
0%
below boiling point
0%
below critical temperature
0%
below inversion temperature
0%
above critical temperature
Explanation
At critical temperature, there will be an equilibrium between the vapors of liquid and gaseous state. The liquid starts changing to gaseous state above critical temperature. Hence, vapor of liquid exist only below critical temperature.
When some
NaCl
was dissolved in water, the freezing point depression was numerically equal to twice the molal
K_f
depression constant. The relative lowering of vapour pressure of the solution is nearly:
Report Question
0%
0.036
0%
0.018
0%
0.0585
0%
0.072
Explanation
\Delta T_f= K_f \cfrac {W_1}{M_1 \times W_2}\times 1000
[
W_2
is given in grams]
where
1
and
2
denote solute & solvent respectively.
Given,
\Delta T_f=2 K_f \Rightarrow \cfrac {W_1 \times 1000}{M_1 \times W_2}= 2
Relative lowering of vapour pressure=
\cfrac {W_1 \times M_2}{M_1 \times W_2}
Here,
M_2
= Molecular weight of
H_2O= 18
\therefore
Relative lowering of vapour pressure=
\left(\cfrac {W_1}{M_1 \times W_2}\right)\times 18
=\cfrac {2}{1000}\times 18
= 0.036
The vapour pressure of pure liquid is
70
Torr at
27^o C
. The vapour pressure of a solution of this liquid and another liquid (mole fraction 0.2) is
84
Torr at
27^o C
. The vapour pressure of pure liquid
B
at
27^o C
is?
Report Question
0%
140
Torr
0%
280
Torr
0%
160
Torr
0%
200
Torr
Explanation
Vapour Pressure of pure liquid
A=70
torr (
P_{A}^{o}
)
Mole fraction of liquid
B=0.2
(
x_{B}
)
Thus mole fraction of liquid
A=x_{A}=1-x_{B}
Total vapour pressure
=84
torr
P=x_{A} P_{A}^{o} + x_{B} P_{B}^{o}
84=(0.8) \times 70 + 0.2 \times P_{B}^{o}
P_{B}^{o}
=140
torr
=
vapour pressure of the pure liquid
B
Hence, the correct option is
\text{A}
{ \Delta }_{ f }{ G }^{ o }
at
500\ K
for substance
S
in liquid state and gaseous state are
+100.7\ kcal\ { mol }^{ -1 }
and
+103\ kcal\ { mol }^{ -1 }
respectively. Vapour pressure of liquid
S
at
500\ K
is approximately equal to:
(R= 2\ { cal }\ K^{ -1 }\ { mol }^{ -1 })
Report Question
0%
0.1\ atm
0%
1\ atm
0%
10\ atm
0%
100\ atm
Explanation
Substance (s)
\rightarrow
Substance (g)
\triangle G^{o}=103-100.7
=2.3\ K\ cal\ mol^{-1}
K_{p}=
Vapour pressure of the substance
K_{p}=P
\triangle G=-RT\ In\ K_{p}
(\because K_{p}=P)
2.3=-2\times 10^{-3}\times 500\ In\ P
2.3=-2\times 500\times10^{-3}\times 2.3\ \log P
\log P=-1
P=0. 1\ atm
A solution has a
1:4
mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at
20^{\circ}C
are
440
mm of
Hg
for pentane and
120
mm of
Hg
for hexane. The mole fraction of pentane in the vapour phase would be?
Report Question
0%
0.549
0%
0.200
0%
0.786
0%
0.478
Explanation
Mole fraction of pentane solution=
\cfrac {1}{1+4}=\cfrac {1}{5}
Mole fraction of hexane solution=
\cfrac {4}{1+4}=\cfrac {4}{5}
Total pressure of solution,
P_S=X_{P}P_P^O+X_HP_H^O
=\cfrac {1}{5}\times 440\ mm\ Hg+\cfrac {4}{5}\times 120\ mm\ Hg
=184\ mm\ Hg
\therefore
The fraction of pentane in the vapour phase
=\cfrac {X_PP_P^O}{P_S}=\cfrac {88}{184}=0.478
.
Hence, the correct option is
D
Vapour pressure of pure benzene is 119 torr and of toluene is 37.0 torr at the same temperature mole fraction of toluene in vapour phase which is in equilibrium with a solution of benzene and toluene having a mole fraction of toluene 0.50, will be:
Report Question
0%
0.137
0%
0.205
0%
0.237
0%
0.435
The amount of solute (mol mass=
60
) that must be added to
180g
of water so that the vapour pressure of water is lowered by
10 \%
is?
Report Question
0%
30
g
0%
60
g
0%
120
g
0%
12
g
20
ml of
1M\ BaCl_2
solution and
25
ml of
0.1
M
Na_2SO_4
are mixed to form
BaSO_4
. The amount of
BaSO_4
precipitated are:
Report Question
0%
2.5
g
0%
2.5
moles
0%
2.5
millimoles
0%
0.05
millimoles
Explanation
BaCl_2+Na_2SO_4\longrightarrow BaSO_4\downarrow +2NaCl
1
mole of
BaCl_2
and
1
mole of
Na_2SO_4
mix to form
1
mole of
BaSO_4
Moles present of
BaCl_2=20\times 1\times 10^{-3}=20\ mmoles
.
Moles of
Na_2SO_4=25\times 0.1\times 10^{-3}=2.5\ mmoles.
\therefore
Moles of
BaSO_4
ppt
=2.5\ mmoles.
A mixture of ethanol and propanol has vapor pressure 279 mm of Hg at 300 K. The mol fraction of ethanol in the solution is 0.6 and vapour pressure of pure propanol is 210 mm of Hg. Vapour pressure of pure ethanol will be:
Report Question
0%
336.6
mm
0%
325
mm
0%
375
mm
0%
415
mm
Explanation
p=p_1+p_2
\Rightarrow p={p_1}^0x_1+{p_2}^0x_2
( Raoult's law )
p={p_1}^0\left( 1-x_2\right) +{p_2}^0x_2
p={p_1}^0+\left( {p_2}^0-{p_1}^0\right) x_2
279mm={p_1}^0+\left( {p_2}^0-{p_1}^0\right) x_2
Let
2,
ethanol
1,
propanol
\therefore 279mm=210mm+\left( {p_2}^0-210\right) 0.6
69=\left( {p_2}^0-210\right)0.6
{p_2}^0-210=115
\Rightarrow {p_2}^0=325mm
Hence, the answer is
325mm.
The vapour pressure of a pure liquid A is 70 torr at 300 K. It forms an ideal solution with another liquid B. The mole fraction of B in the solution is 0.2 and total pressure of solution is 84 torr at 300 K. The vapour pressure of pure liquid B at 27C is ?
Report Question
0%
0.14 torr
0%
560 torr
0%
140 torr
0%
70 torr
Explanation
Solution:- (C)
140 \text{ torr.}
Mole fraction of
B = 0.2
As we know that,
{x}_{A} + {x}_{B} = 1
\Rightarrow {x}_{A} = 1 - 0.2 = 0.8
{{p}^{°}}_{A} = 70 \text{ torr.}
{{p}^{°}}_{B} = ?
{p}_{total} = 84 \text{ torr.}
From Dalton's law of partial pressure,
{p}_{total} = {p}_{A} + {p}_{B} ..... \left( 1 \right)
From Raoult's law of vapour pressure,
{p}_{A} = {{p}^{°}}_{A} \cdot {x}_{A}
\Rightarrow {p}_{A} = 70 \times 0.8 = 56
Again, from Raoult's law of vapour pressure,
{p}_{B} = {{p}^{°}}_{B} \cdot {x}_{B}
{p}_{B} = {{p}^{°}}_{B} \times 0.2
Substituting these values in equation
\left( 1 \right)
, we have
84 = 56 + 0.2 \times {{p}^{°}}_{B}
\Rightarrow {{p}^{°}}_{B} = \cfrac{84 - 56}{0.2} = 140 \text{ torr.}
Hence the vapour pressure of pure liquid
B
is
140 \text{ torr.}
.
The boiling point of
C_{6}H_{6},CH_{3}OH, C_{6}H_{5}NH_{2}
and
C_{6}H_{5}NO_{2}
are
80^{\circ},\ 65 ^{\circ},\ 184^{\circ}
and
212^{\circ}
respectively. Which will show highest vapourr pressure at room temperature?
Report Question
0%
C_{6}H_{6}
0%
CH_{3}OH
0%
C_{6}H_{5}NH_{2}
0%
C_{6}H_{5}NO_{2}
Explanation
Boiling point is the temperature at which the vapor pressure of a liquid become equal to atmospheric pressure.
\rightarrow
So, the compounds which has low boiling point will have high vapor pressure.
\rightarrow
Given
{ CH }_{ 3 }OH
has boiling point of
{ 65 }^{ 0 }
.
\rightarrow
It has highest vapor among given with
0.166
atm.
Ans :- Option B.
For a non-electrolytic solution, van't Hoff factor is equal to:
Report Question
0%
0
0%
1
0%
2
0%
0\quad <\quad i\quad \le \quad 1
Explanation
Van't Hoff factor is more than 1 for the strong electrolytes which will dissociated and forms more than one ion.
Van't Hoff factor for weak electrolytes and non-electrolytes is equal to 1
Van't Hoff factor is less than 1 for the molecules which will tend to associate to form dimer molecules.
One mole of non volatile solute is dissolved in two moles of water. The vapour pressure of the solution relative to that of water is:
Report Question
0%
\dfrac{2}{3}
0%
\dfrac{1}{3}
0%
\dfrac{1}{2}
0%
\dfrac{3}{1}
Explanation
Relative lowering in vapor pressure
=\cfrac{P^{\circ}-P_s}{P^{\circ}}=x_A
Where
x_A=
mole fraction of non-volatile solute.
\therefore \cfrac{P^{\circ}-P_s}{P^{\circ}}=\cfrac{1}{3}\\ \therefore \cfrac{P_s}{P^{\circ}}=1-\cfrac{1}{3}=\cfrac{2}{3}
Hence, the correct option is
A
If
P^o
and
P^s
are the vapour pressure of the solvent and solution respectively.
n_ 1
and
n_2
are the mole fraction of the solvent and solute respectively, then
?
Report Question
0%
P^S=P^o n_1
0%
P^S=P^o n_2
0%
P^o=P^S n_2
0%
P^S=P^o \dfrac { { n }_{ 1 } }{ { n }_{ 2 } }
A mixture of ethyl alcohol and propyl alcohol has vapour pressure of
290mm
at
300K
. The vapour pressure of propyl alcohol is
200mm
. If mole fraction of ethyl alcohol is
0.6
its vapour presssure at same temperature will be:-
Report Question
0%
360
0%
350
0%
300
0%
700
Explanation
as
P_{sol} = X_{sol} . P^o_{sol}
X \rightarrow
mole fraction
P^o \rightarrow
pure vapour pressure of solution
290 mm =X_{ethanal} . P^o_{ethanal} + X_{propanal} . P^o_{propanal}
290 mm =0.6 \times P^o_{ethanal} + (1-0.6) \times 200 mm
on solving
P^o_{ethanal} =350
nm
Vapour pressure diagram of some liquids plotted against temperature are shown below most volatile liquid is
Report Question
0%
A
0%
B
0%
C
0%
D
Explanation
In this diagram the most volatile liquid is because is have maximum vapour pressure.
Two liquids, A and B, form an ideal solution. At the specified temperature, the vapour pressure of pure A is 200 mm Hg while that of pure B is 75 mm Hg. If the vapour over the mixture consists of 50 mol percent A, what is the mole percent A in the liquid?
Report Question
0%
20
0%
76
0%
27
0%
65
The relative decrease in vapour pressure of an aqua solution containing 2 moles of
4NaCl
in 3 moles of
{H}2_{O}
is 0.On reaction with
AgNO_3
this solution will form:
Report Question
0%
1 mol of
AgCl
0%
0.25 mol of
AgCl
0%
2 mol of
AgCl
0%
0.4 mol of
AgCl
An ideal solution contains two volatile liquids
A\left( p=100\ torr \right)
and
B\left( p=200\ torr \right)
. If mixture contain 1 mole of
A
and 4 mole of
B
then total vapour pressure of the distillate is:
Report Question
0%
150
0%
180
0%
188.88
0%
198.88
Explanation
Solution:- (B)
180
Given:-
No. of moles of A
\left( {n}_{A} \right) = 1 \text{ mole}
No. of moles of B
\left( {n}_{B} \right) = 4 \text{ moles}
As we know that,
\text{mole fraction} = \cfrac{\text{no. of moles}}{\text{total moles}}
Therefore,
{x}_{A} = \cfrac{1}{1 + 4} = 0.2
{x}_{B} = \cfrac{4}{1+4} = 0.8
Again, as we know that,
{P}_{T} = {P}_{A} + {P}_{B}
\Rightarrow {P}_{T} = \left( {x}_{A} \times {{p}^{°}}_{A} \right) + \left( {x}_{B} \times {{p}^{°}}_{B} \right)
Given:-
{{p}^{°}}_{A} = 100 \text{ torr.}
{{p}^{°}}_{B} = 200 \text{ torr.}
\therefore {P}_{T} = \left( 0.2 \times 100 \right) + \left( 0.8 \times 200 \right)
\Rightarrow {P}_{T} = 20 + 160 = 180 \text{ torr.}
Hence the total vapour pressure of the distillate is
180 \text{ torr.}
.
The vapour pressure of water is
12.3k \, Pa
at
300K
. Calculate the vapour pressure
1
molal solution of a non-volatile solute in it.
Report Question
0%
12.08 \ kPa
0%
1.208 \ Ppa
0%
2.4 \ kPa
0%
0.4 kPa
Explanation
1
molal solution means 1 mol of the solute is present in
1000 g
of the solvent (water).
The molar mass of water
= 18 g
mol^{- 1}
Number of moles present in
1000
g of water
= 1000/18
= 55.56 \ mol
Therefore, the mole fraction of the solute in the solution is
x_2 = 1 / (1+55.56)
= 0.0177
It is given that,
Vapour pressure of water,
P^0_1
= 12.3 kPa
Applying the relation,
(P^0_1 - P_1) / P^0_1 = X_2
= (12.3 - P_1) / 12.3
=0.0177
= 12.3 - P_1
= 0.2177
= P_1
= 12.0823
= 12.08 kPa
An ideal solution if obtained by mixing
CH_3 CHBr_2
and
CH_2Br - CH_2Br
in the ratio
2:1
P^o_{CH_3CHBr_2} = 173, P^o_{CH_2BrCH_2Br} = 127
. Thus total vapour pressure is:
Report Question
0%
158
0%
257
0%
137
0%
197
Explanation
P = Po_1x_1 + Po_2x_2
x_1 = \dfrac{2}{2 +1} = \dfrac{2}{3}
x_2 = \dfrac{1}{3}
Total pressure
= P
Partial pressure of
CH_3CHBr_2 = Po_1
Partial pressure of
CH_3BrCH_2Br = Po_2
Mole fraction
CH_3CHBr_2 = x_1
Mole fraction
CH_3CHBrCH_2Br = x_2
P = 173 \times \dfrac{2}{3} + 127 \times \dfrac{1}{3}
P = 158
.
Two liquids A and B have
{P}_{A}^{o}
and
{P}_{B}^{o}
in the ratio
1:3
and the ratio of number of moles of
A
and
B
in liquid phase are
1:3
. Then mole fraction of A in vapour phase in equilibrium with the solution is equal to:
Report Question
0%
0.1
0%
0.2
0%
0.5
0%
1.0
Explanation
Partial pressure of
A=K\times\cfrac{1}{4},
where
K
is ratio constant.)
Partial pressure of
B=3K\times \cfrac{3}{4}
Total pressure is
\cfrac{10K}{4}
.
Vapor phase mole fraction of
A
is,
\cfrac{\text{Partial pressure of }A}{\text{Total pressure}}=\cfrac{K\times \cfrac{1}{4}}{\cfrac{10K}{4}}=\cfrac{1}{10}=0.1
In an ideal solution of non-volatile solute B in solvent A in 2: 5 molar ratio has vapour pressure 250 mm. If another solution in ratio 3: 4 prepared then vapour pressure above this solution is:
Report Question
0%
200 mm
0%
250 mm
0%
350 mm
0%
400 mm
Explanation
Given molar ratio
=2:5
v.p
=250\ mm\left(\text{one solute}\right)
Moral ratio
=3:4\quad v.p=? \quad\left(\text{another solute}\right)
Mole fraction of solven
=\dfrac{5}{2+5}=\dfrac{5}{4}=0.71\quad \left({1}^{st}{\text{solute}}\right)
According to Raoult's law;
p
(solution)
\times
mole fraction of solven
\Rightarrow250=p\left(\text{pure solvent}\right)0.71
p\left(\text{pure solvent}\right)= \dfrac{250}{0.71}=352.11\ mm
mole fraction of solvent
=\dfrac{4}{3+4}=\dfrac{4}{7}=0.57
p\left(\text{solution}\right)=352.11\times 0.57=200.7\approx 200\ mm
Hence, the correct option is
A
Calculate the vapour pressure of a solution at
100^oC
containing 3 g of cane sugar in 33 g of water. (Atomic weight of
C =12\ u,H=1\ u,O=16\ u
)
Report Question
0%
760 mm Hg
0%
756.9 mm Hg
0%
758.3 mm Hg
0%
None of these
A sample of drinking water was found to be severely contaminated with chloroform,
{CHCl}_{3}
, supposed to be a carcinogen. The level of contamination was
15
ppm (by mass). Express this in percent by mass.
Report Question
0%
1.5\times {10}^{-3}
0%
4.0\times {10}^{-3}
0%
6\times {10}^{-3}
0%
0.75\times {10}^{-3}
Explanation
15 ppm means
15
parts in million
(10^6)
parts
\%\,by\,mass=\dfrac{15\times 100}{10^{6}}=15\times 10^{-4}
=1.5\times 10^{-3}
Hence, the correct option is
\text{A}
In steam distillation, the vapour pressure of the volatile organic compound is:
Report Question
0%
equal to atmospheric pressure
0%
less than atmospheric pressure
0%
more than atmosphetic pressure
0%
none of the above
Explanation
In steam distillation, the vapour pressure of the volatile compound is less than the atmospheric pressure.
A sample of 16g charcoal was brought into contact with
C{ H}_{ 4}
gas contained in a vessel of 1 litre at
2{ 7 }^{0 }C
. The pressure of gas was found to fall from 760 to 608 torr. The density of charcoal sample is 1.6g/
c{ m}^{ 3 }
. What is the volume of the
C{ H}_{ 4}
gas adsorbed per gram of the adsorbent at 608 torr and
2{ 7 }^{0 }C
?
Report Question
0%
125 mL/g
0%
16.25 mL/g
0%
26 mL/g
0%
None of these
Explanation
Final volume of gas, at
608
torr pressure
V_{2} = \dfrac{P_1V_1}{P_2}
= \dfrac{760 \times 1}{608}
\Rightarrow
1.25
or
V_2 = 1250\,mL
Volume occupied by gas = Volume of vessel - Volume occupied by charcoal
= 1000 - \dfrac{16}{1.6} = 990 \,mL
Difference of volume is due to adsorption of gas by charcoal.
\therefore
Volume of gas adsorbed by charcoal
= 1250 - 990
\Rightarrow 260\,mL
Volume of the gas adsorbed per gram of charcoal
= \dfrac{260}{16} = 16.25\,mL / g
at
608
torr and
27^{\circ}C
.
The gas Z in the above fraction is ?
Report Question
0%
Nitrous oxide
0%
Nitric Oxide
0%
Dinitrogen tetroxide
0%
Nitrogen dioxide
100\ ml
of an aqueous solution contains
6.0\times {10}^{21}
solute molecules. The solution is diluted to
1
lit. The number of solute molecules present in
10\ ml
of the dilute solution is:
Report Question
0%
6.0\times {10}^{20}
0%
6.0\times {10}^{19}
0%
6.0\times {10}^{18}
0%
6.0\times {10}^{17}
Explanation
100 ml solution diluted to 1 liters (1000) ml
contains
6.0 \times 10^{21}
solute molecular
No of molecules present in 10 ml
= \dfrac{10 \times 6.0 \times 10 ^{21}}{1000} = 6 \times 10 ^{19}
Lowering in vapour pressure is highest for:
Report Question
0%
0.2m
urea
0%
0.1m
glucose
0%
0.1m \, MgSO_4
0%
0.1m \, BaCl_2
Explanation
Lowering in vapour pressure is directly proportional
to molality which in turn is directly proportional
to n factor (no. of ions it gives)
The concentration of urea, i.e,
0.2 \ M
is much
more than glucose,
MgSO_{4}
&
BaCl_{2}
Therefore urea will have greater molality &
therefore it will have highest vapour pressure.
Ans is A)
0.2 M
urea
Normal boiling point of a liquid is that temperature at which vapour of the liquid pressure of the liquid is equal to:
Report Question
0%
zero
0%
380mm of Hg
0%
760mm of Hg
0%
100mm of Hg
A solution X contains 30 mole percent of A and is in equilibrium with its vapour that contains 40 mole percent of B. The ratio of vapour pressure of pure A and B will be
Report Question
0%
2 : 7
0%
7 : 2
0%
3 : 4
0%
4 : 3
Explanation
From Raoult's law
.. PA = (P*A) x (χA)
.. PB = (P*B) x (χB).. .. .. . χB is mole fraction B in LIQUID phase
and from Daltons law
.. PA = yA x Ptotal
.. PB = yB x Ptotal.. .. ... ...yB is mole fraction B in VAPOR phase
subbing
.. yA x Pt = (P*A) x (χA)
.. yB x Pt = (P*B) x (χB)
dividing
.. (yA / yB) x (Pt / Pt) = (P*A / P*B) x (χA / χB)
simplifying and rearranging
.. (P*A / P*B) = (yA / yB) x ((χB / χA)
and finally
.. (P*A / P*B) = (60 / 40) x (70 / 30) = 3.5
From Raoult's law
.. PA = (P*A) x (χA)
.. PB = (P*B) x (χB).. .. .. . χB is mole fraction B in LIQUID phase
and from Daltons law
.. PA = yA x Ptotal
.. PB = yB x Ptotal.. .. ... ...yB is mole fraction B in VAPOR phase
subbing
.. yA x Pt = (P*A) x (χA)
.. yB x Pt = (P*B) x (χB)
dividing
.. (yA / yB) x (Pt / Pt) = (P*A / P*B) x (χA / χB)
simplifying and rearranging
.. (P*A / P*B) = (yA / yB) x ((χB / χA)
and finally
.. (P*A / P*B) = (60 / 40) x (70 / 30) = 3.5
From Raoult's law
.. PA = (P*A) x (χA)
.. PB = (P*B) x (χB).. .. .. . χB is mole fraction B in LIQUID phase
and from Daltons law
.. PA = yA x Ptotal
.. PB = yB x Ptotal.. .. ... ...yB is mole fraction B in VAPOR phase
subbing
.. yA x Pt = (P*A) x (χA)
.. yB x Pt = (P*B) x (χB)
dividing
.. (yA / yB) x (Pt / Pt) = (P*A / P*B) x (χA / χB)
simplifying and rearranging
.. (P*A / P*B) = (yA / yB) x ((χB / χA)
and finally
.. (P*A / P*B) = (60 / 40) x (70 / 30) = 3.5
Which of the following is an ideal solution
Report Question
0%
Water + ethanol
0%
Chloroform + carbon tetrachloride
0%
Benzene + toluene
0%
Water + hydrochloric acid
Explanation
A solution of ethyl alcohol and water shows positive deviation from Raoult's law due to the presence of hydrogen bonding present in the ethyl alcohol solution and water molecules
Chloroform + carbon tetrachloride show positive deviation from Raoult's law
Water + HCl is a non-ideal solution showing negative deviations from Raoult's law.
In a Benzene-toluene mixture, A-B interactions are almost equal to A-A and B-B interactions due to the very small difference in the two compounds, i.e., they differ just by one CH2 group. Hence, no deviation will occur from Raoult's law.
The concentration of a salt solution in terms of mass by mass percentage is
20\%
and the mass of the solution is
550 g.
What is the mass of solute present in the solution?
Report Question
0%
110g
0%
105g
0%
205g
0%
210g
Explanation
Given that:
The mass percentage of the solution is 20%.
The mass of the solution is 550g.
The mass of the solute can be calculated by using the formula given below.
{\rm{Mass}}\;{\rm{percentage}} = \dfrac{{{\rm{Mass}}\;{\rm{of}}\;{\rm{solute}}}}{{{\rm{Mass}}\;{\rm{of}}\;{\rm{solution}}}} \times 100
The mass of solute can be calculated as,
\begin{align*}{\rm{Mass}}\;{\rm{of}}\;{\rm{solute}} &= \dfrac{{{\rm{Mass}}\;{\rm{percentage}}}}{{{\rm{Mass}}\;{\rm{of}}\;{\rm{solution}}}} \times 100\\ &= \dfrac{{20}}{{100}} \times 550\;{\rm{g}}\\ &= 110\;{\rm{g}}\end{align*}
Therefore, the mass of solute is 110 g.
The vapour pressure of a solution containing 5 g of a non electrolyte in 100 g of water at a particular temperature is
2985 N{m}^{-2}
. If the vapour pressure of pure water is
3000 N{m}^{-2}
, the molecular weight of solute is:
Report Question
0%
60
0%
120
0%
180
0%
380
Explanation
we have formula of
\text{Relative lowering of vapour pressure}
which is
\dfrac{P_o-P}{P_o}=X_{solute}=\dfrac{n_{solute}}{n_{solute}+n_{solvent}}\approx\dfrac{n_{solute}}{n_{solvent}}
Now, pute the values
\dfrac{3000-2985}{3000}=\dfrac{\dfrac{5}{M}}{\dfrac{100}{18}}
\dfrac{15}{3000}=\dfrac{5\times 18}{100\times M}
M=180
correct answer is C.
The temperature and pressure at which ice, liquid. water and water vapour can exist together are ?
Report Question
0%
{ 0 }^{ o }C,\quad 1 atm
0%
{ 2 }^{ o }C,\quad 4.7atm
0%
{ 0 }^{ o }C,\quad 4.7mm
0%
{ -2 }^{ o }C,\quad 4.7mm
Explanation
The temperature and pressure at which ice, liquid, water and water vapour exist together at triple point of water.
Triple point of water is
0^\circ C \ and \ 4.7mm
Hence, Option "C" is the correct answer.
All form ideal solution except
Report Question
0%
C_2H_5Br
and
C_2H_5I
0%
C_6H_5Cl
and
C_6H_5Br
0%
C_6H_6
and
C_6H_5CH_3
0%
C_2H_5I
and
C_2H_5OH
Explanation
The following forms an ideal solution
C_2H_5Br + C_2H_5I
C_6H_5Cl + C_6H_5Br
C_6H_6 + C_6H_5CH_3
\text{As we know,} C_2H_5OH \text{ shows H-bonding as well as it is polar so it will not make an ideal solution. }
thus, the correct answer is D.
Vapour pressure is _________ dependent property.
Report Question
0%
Temperature
0%
Pressure
0%
Volume
0%
Density
Explanation
Vapour pressure is temperature-dependent property.
As the
temperature
of liquid increases, the kinetic energy of its molecules also increases and as the kinetic energy of the molecules increases, the number of molecules transitioning into a
vapour
also increases, thereby increasing the
vapour pressure
.
The solubility of a specific non-volatile salt is
4\mathrm { g }
in
100\mathrm { g }
of water at
25 ^ { \circ } \mathrm { C } .
If
2.0 g,
4.0\mathrm g
and
6.0 g
of the salt added of
100 g
of water at
25 ^ { \circ } \mathrm { C } ,
in system
X , Y
and
Z .
The vapour pressure would be in the order:
Report Question
0%
X < Y < Z
0%
X > Y > Z
0%
Z > X = Y
0%
x > Y = z
At
250^{o}C
and
1
atmosphere pressure, the vapour density of
PCI_{5}
is
57.9
. What will be the dissociation of
PCI_{5}-
Report Question
0%
1.00
0%
0.90
0%
0.80
0%
0.65
Explanation
A solution
X
of
A
and
B
contains
30
mole
\%
of
A
& is in equilibrium with its vapour that contains
40
mole
\%
of
B
. The ratio of
V.P
of pure,
A
and
B
will be?
Report Question
0%
2:7
0%
7:2
0%
3:4
0%
4:3
The vapour pressure of water at
20^0C
is 17.54 mm. When 20 g of non-ionic, substance is dissolved in 100 g of water, the vapour pressure is lowered by 0.30 mm.What is the molecular weight of the substances.
Report Question
0%
210.2
0%
208.16
0%
215.2
0%
200.8
The boiling points of
C_6H_6, CH_3OH, C_6H_5 NH_2
and
C_6H_5NO_2
are
80^0C, \ 65^0C
and
212^0C
respectively. Which of the following will have highest vapour pressure at room temperature?
Report Question
0%
C_6H_6
0%
CH_3OH
0%
C_6H_5NH_2
0%
C_6H_5NO_2
Explanation
(B)
CH_{3}OH
Because boiling point is the temp.
at which the vapour pressure of
liquid becomes equal to atm. pressure
methanol have lowest boiling pt.
\therefore
will show highest vapour pressure.
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