Purification of Organic Compounds Questions in English

(C) The movement of the solvent and the solute on chromatography paper is based on the principle of $capillary \ action$.
In paper chromatography,the stationary phase is water trapped in the cellulose fibers of the paper,and the mobile phase moves through the paper via $capillary \ action$.

(N/A) The principle of extraction in a separatory funnel is based on the difference in the solubility of an organic compound in two immiscible solvents,typically an organic solvent and water. The organic compound is more soluble in the organic solvent than in water,allowing it to be separated from an aqueous solution by shaking it with the organic solvent.

(B) Distillation is the technique used to separate a volatile liquid from a non-volatile impurity. In this process,the liquid is heated to its boiling point to form vapor,which is then condensed back into a liquid,leaving the non-volatile impurity behind in the distillation flask.

(N/A) $(i)$ Distillation under reduced pressure (or vacuum distillation) is used because the liquid decomposes below its boiling point.
$(ii)$ Sublimation is used because camphor is a sublimable solid,while $BaSO_4$ is non-sublimable.

(A) The retardation factor $(R_f)$ is calculated using the formula: $R_f = \frac{\text{Distance travelled by the compound}}{\text{Distance travelled by the solvent front}}$.
For compound $(A)$: $R_f(A) = \frac{8 \, cm}{10 \, cm} = 0.8$.
For compound $(B)$: $R_f(B) = \frac{6 \, cm}{10 \, cm} = 0.6$.
Therefore,the $R_f$ values are $0.8$ and $0.6$ respectively.

(A) The $R_f$ value is defined as the ratio of the distance traveled by the substance to the distance traveled by the solvent front.
$R_f = \frac{\text{distance traveled by substance}}{\text{distance traveled by solvent front}}$.
Since $R_f$ for $X$ is $0.7$ and $R_f$ for $B$ is $0.4$,compound $X$ has traveled a greater distance relative to the solvent front.
Therefore,compound $X$ migrates more.

(A) In column chromatography,the component with the lower $R_f$ value interacts more strongly with the stationary phase and moves slower down the column.
Conversely,the component with the higher $R_f$ value interacts less with the stationary phase and moves faster.
Therefore,the component with the higher $R_f$ value is eluted (obtained) first.
Since $R_f(X) = 0.75$ and $R_f(Y) = 0.25$,$X$ will be obtained first.

(A) Sublimation is a technique used to separate substances that sublime upon heating.
Common organic compounds purified by this method include:
$(i)$ Camphor
$(ii)$ Naphthalene
$(iii)$ Anthracene
$(iv)$ Benzoic acid
Therefore,the correct pair is Camphor and Naphthalene.

(A) The correct matches are as follows:
$(i)$ Aniline and chloroform have a large difference in boiling points,so they are separated by $(s)$ Simple distillation.
$(ii)$ An aqueous solution of a compound is separated using $(r)$ Differential extraction.
$(iii)$ $A$ mixture of liquids with a small difference in boiling points is separated by $(q)$ Fractional distillation.
$(iv)$ Aniline is purified using $(p)$ Steam distillation.
Therefore,the correct sequence is $(i-s, ii-r, iii-q, iv-p)$.

(A) The correct matches are as follows:
$(i)$ Differential extraction is performed using a $(q)$ Separatory funnel.
$(ii)$ Steam distillation is used for substances that are $(s)$ Liquid decompose at high temperature.
$(iii)$ Distillation at low pressure is performed using a $(t)$ Vacuum pump.
$(iv)$ Simple distillation is used for liquids with a $(p)$ High difference of boiling point.
$(v)$ Fractional distillation is used to separate $(r)$ Component of petroleum.
Therefore,the correct sequence is: $(i-q, ii-s, iii-t, iv-p, v-r)$.

(A) The correct matches are:
$(i)$ Liquid boiled at low temperature is achieved by $(d)$ Distillation under reduced pressure.
$(ii)$ Glycerol from lye is purified by $(c)$ Steam distillation (or distillation under reduced pressure,but in standard contexts,it is associated with distillation under reduced pressure; however,given the options,$(c)$ is often used for volatile substances,while $(d)$ is specific for heat-sensitive liquids like glycerol).
$(iii)$ The liquid with lower boiling point condenses first in $(b)$ Simple distillation.
$(iv)$ The liquid with higher boiling point condenses first in $(a)$ Fractional distillation.
Thus,the correct sequence is $(i-d), (ii-c), (iii-b), (iv-a)$.

(N/A) $(i) \text{ False, } (ii) \text{ False, } (iii) \text{ True, } (iv) \text{ False}$.
Explanation:
$(i)$ Volatile liquids are purified by distillation,but the choice between simple and fractional depends on the boiling point difference.
$(ii)$ Two liquids can be separated by simple or fractional distillation depending on their boiling points,not just fractional.
$(iii)$ Fractional distillation is specifically used when the boiling point difference is small (less than $20 \ K$).
$(iv)$ Liquids with a large difference in boiling points are separated by simple distillation,not fractional.

(N/A) $(i) - \text{True}, (ii) - \text{False}, (iii) - \text{False}, (iv) - \text{False}$.
$(i)$ Crystallisation is a standard method for the purification of solid organic compounds.
$(ii)$ Crystallisation is used for solids,while distillation is used for liquids. The statement is false because it incorrectly claims distillation purifies solids.
$(iii)$ Sublimation is used to purify solids that sublime on heating,not liquids.
$(iv)$ Ammonium chloride $(NH_4Cl)$ is a sublimable solid,while sodium chloride $(NaCl)$ is not. Therefore,sublimation is used to separate this mixture,not distillation.

(A) $(i)$ True: Chloroform has a boiling point of $334 \ K$ and aniline has $457 \ K$.
$(ii)$ False: Since chloroform has a lower boiling point $(334 \ K)$ compared to aniline $(457 \ K)$,it will vaporize first during distillation.
$(iii)$ True: Substances with lower boiling points are more volatile. Since chloroform $(334 \ K)$ has a lower boiling point than aniline $(457 \ K)$,it is more volatile.

(A) The correct statements are:
$(i)$ True: Steam distillation allows liquids to boil at temperatures below their normal boiling points.
$(ii)$ True: The liquid boils when the sum of its vapour pressure and the water's vapour pressure equals atmospheric pressure,meaning the liquid's individual vapour pressure is less than atmospheric pressure.
$(iii)$ True: This is the fundamental principle of steam distillation where $P_{total} = P_{liquid} + P_{water} = P_{atm}$. (Note: The original provided solution was incorrect; the correct sequence is $(i-T, ii-T, iii-T, iv-T, v-T)$).
$(iv)$ True: The distillate collected is a mixture of the organic liquid and water.
$(v)$ True: The vapours are condensed to form the liquid mixture.

(A) The correct statements are:
$i$. True (It is used to separate glycerol from spent lye in the soap industry).
$ii$. False (Vacuum pumps are used,but air pumps are generally not used for this purpose).
$iii$. True (Distillation at reduced pressure prevents the decomposition of heat-sensitive substances).
$iv$. False (The process is specifically designed to prevent decomposition).
$v$. True (Reducing the pressure lowers the boiling point of the liquid).
Summary: $i-T, ii-F, iii-T, iv-F, v-T$.

(N/A) $(i)$ False,$(ii)$ True,$(iii)$ True,$(iv)$ False.

(N/A) $1$. Half-headed curved arrow (fish-hook arrow)
$2$. $100$
$3$. Small,large
$4$. Fractional distillation

(N/A) $(1)$ The steam distillation of $\text{immiscible}$ liquid is done and it is boiled at $\text{lower}$ temperature.
$(2)$ $\text{Vacuum pump}$ and $\text{water pump}$ are used to reduce pressure in distillation under reduced pressure.
$(3)$ In steam distillation the equation of total vapour pressure is $P = p_1 + p_2$ where $p_1$ is more than $\text{vapour pressure of water } (p_2)$.
$(4)$ $\text{Separatory funnel}$ apparatus is used in differential extraction.

(N/A) $1$. The organic layer is above because its density is less than that of water.
$2$. Immiscible.
$3$. Less.
$4$. $AgNO_3$ (Silver nitrate).

(C) liquid that decomposes at its boiling point can be purified by distillation under reduced pressure because the boiling point decreases as pressure decreases.
Since the compound is also steam volatile and insoluble in water,it can be purified by steam distillation.
Therefore,both methods are suitable for its purification.

(N/A) The suitable method to separate these two compounds is $Simple \ Distillation$.
Reason: The boiling points of the two components are $97\,^{\circ}C$ and $68\,^{\circ}C$. The difference in their boiling points is $97\,^{\circ}C - 68\,^{\circ}C = 29\,^{\circ}C$. Since the difference in boiling points is greater than $20\,^{\circ}C$,$Simple \ Distillation$ is effective. In this process,the component with the lower boiling point $(68\,^{\circ}C)$ vaporizes first,leaving the component with the higher boiling point $(97\,^{\circ}C)$ behind in the distillation flask.

(A-1, B-2, C-3, D-4, E-5) The correct matches are as follows:
$A$. Two solids with different solubilities in a solvent are separated by $1$. Crystallisation.
$B$. Liquids that decompose at their boiling point are purified by $2$. Distillation under reduced pressure.
$C$. Steam volatile liquids are separated by $3$. Steam distillation.
$D$. Two liquids with boiling points close to each other are separated by $4$. Fractional distillation.
$E$. Two liquids with a large difference in boiling points are separated by $5$. Simple distillation.
Thus,the correct sequence is $A-1, B-2, C-3, D-4, E-5$.

(N/A) Benzoic acid can be purified from hot water because of the following characteristics:
$(i)$ Benzoic acid is more soluble in hot water and less soluble in cold water.
$(ii)$ Impurities associated with benzoic acid are either insoluble in water or are more soluble in water to such an extent that when a hot saturated solution of benzoic acid is cooled,the impurities remain in the solution.

(N/A) In steam distillation,the vapour of the organic compound and water are distilled out. Steam (water vapour) is passed into the liquid that is to be purified.
Consequently,the vapour of the liquid and the vapour of water rise and pass into the condenser. The liquid and water are immiscible and form separate layers.
When the sum of the partial vapour pressures of the liquid $(p_1)$ and water $(p_2)$ becomes equal to the atmospheric pressure $(p)$,distillation takes place.
Mathematically,$p = p_1 + p_2$. Since $p_1 < p$,the liquid distills at a temperature lower than its normal boiling point.
Therefore,steam distillation takes place at a lower temperature than the boiling point of the organic liquid,preventing thermal decomposition.

(C) Glycerol has a high boiling point and tends to decompose at its boiling point. Therefore,it is separated from spent lye in soap industries by distillation under reduced pressure,which lowers its boiling point and prevents decomposition.

(C) Paper chromatography is based on the principle of partition chromatography.
In this technique,the substances are distributed or partitioned between two liquid phases.
The stationary phase is the water molecules held in the pores of the filter paper,while the mobile phase is a solvent or mixture of solvents that moves over the paper.

(B) Steam distillation is a separation technique used for substances that are steam volatile and immiscible with water.
In this process,the compound vaporizes at a temperature lower than its boiling point,allowing for purification without decomposition.

(B) Paper chromatography is a technique based on partition chromatography,where the stationary phase is water trapped in the cellulose fibers of the paper and the mobile phase is a solvent.
Option $B$ is incorrect because paper chromatography is a method or technique,not a stationary phase itself.
The stationary phase is the water held by the paper,not the paper itself.

(D) In chromatography technique,the separation and purification of a compound depend on the differential distribution of the substance between the stationary phase and the mobile phase. This process relies on factors such as the solubility of the compound in the solvent,the mobility of the solvent system,and the length of the column or $TLC$ plate. However,the purification process is independent of the physical state (solid,liquid,or gas) of the pure compound itself.

(C) $R_f$ (Retardation factor) is defined as the ratio of the distance travelled by the substance to the distance travelled by the solvent front from the reference line.
$R_f = \frac{\text{Distance travelled by the substance from reference line (cm)}}{\text{Distance travelled by the solvent from reference line (cm)}}$
Since $R_f$ is a ratio of two identical units (length),it is a dimensionless quantity. Thus,Statement-$I$ is false.
The $R_f$ value of a compound depends on the nature of the solvent and the stationary phase used. Therefore,it is not constant for all solvents. Thus,Statement-$II$ is false.

(C) The $R_{f}$ value is calculated using the formula:
$R_{f} = \frac{\text{Distance travelled by compound from base line}}{\text{Distance travelled by solvent from base line}}$
From the chromatogram:
Distance travelled by compound $A$ from the base line $= 2 \, cm$
Distance travelled by solvent front from the base line $= 5 \, cm$
Therefore,$R_{f} = \frac{2}{5} = 0.4$
Expressing this as $\times 10^{-1}$:
$0.4 = 4 \times 10^{-1}$
Thus,the value is $4$.

(D) The boiling point of propanone is approximately $56^{\circ}C$ and the boiling point of propanol is approximately $97^{\circ}C$.
Since the difference in their boiling points is $97^{\circ}C - 56^{\circ}C = 41^{\circ}C$,which is greater than $20^{\circ}C$,they can be separated by simple distillation.
Therefore,both Assertion $(A)$ and Reason $(R)$ are correct,and Reason $(R)$ is the correct explanation of Assertion $(A)$.

(D) Reduced pressure distillation (also known as vacuum distillation) is used for the purification of high boiling organic liquids that decompose at or below their boiling point. By reducing the pressure,the boiling point of the liquid is lowered,allowing it to boil and vaporize without reaching the temperature at which it would decompose.

(A) separating funnel is a piece of laboratory glassware used in liquid-liquid extractions to separate the components of a mixture into two immiscible solvent phases of different densities.
It typically has a pear-shaped body with a stopper at the top and a stopcock at the bottom to control the flow of the lower layer.
The structure shown in image $208873-a$ represents a standard separating funnel.

(C) In Thin Layer Chromatography $(TLC)$,the separated components are often invisible to the naked eye. To visualize them,several techniques are used:
$1$. $I_{2}$ (Solid) chambers: Iodine vapors adsorb onto the components,making them visible.
$2$. $U.V.$ Light: Many organic compounds fluoresce under $U.V.$ light.
$3$. Spraying of an appropriate reagent: Chemical reagents react with the components to produce colored spots.
However,adding a visualization agent directly to the mobile phase is not a standard technique for spotting components on a $TLC$ plate,as it would interfere with the separation process itself.

(D) $p-$nitrophenol exhibits intermolecular hydrogen bonding,while picric acid ($2,4,6-$trinitrophenol) exhibits intramolecular hydrogen bonding.
Due to these differences in hydrogen bonding,they possess different polarities and adsorption characteristics on a stationary phase like silica gel.
For a small quantity like $100 \ mg$,chromatographic techniques are highly effective.
Preparative $TLC$ is a suitable technique for separating small amounts of mixtures based on differences in their $R_f$ values.

(D) Chloroform and Aniline are separated by $(III)$ Distillation because they have different boiling points.
$(B)$ Benzoic acid and Naphthalene are separated by $(IV)$ Crystallisation based on differences in their solubilities in a suitable solvent.
$(C)$ Water and Aniline are separated by $(I)$ Steam distillation as Aniline is steam volatile and immiscible with water.
$(D)$ Naphthalene and Sodium chloride are separated by $(II)$ Sublimation because Naphthalene sublimes while Sodium chloride does not.

(A) Thin layer chromatography $(TLC)$ is a type of adsorption chromatography.
It involves the separation of substances of a mixture over a thin layer of an adsorbent coated on a glass plate.
$A$ thin layer (about $0.2 \ mm$ thick) of an adsorbent,such as silica gel or alumina,is spread over a glass plate of suitable size.
Since the separation is based on the differential adsorption of the components on the stationary phase (silica gel),both the Assertion $(A)$ and the Reason $(R)$ are true,and $(R)$ is the correct explanation of $(A)$.

(B)
Aniline can be purified by steam distillation. This method is used to separate compounds that are steam volatile and insoluble in water. In this process,steam from a generator is passed through a flask containing the liquid to be distilled. The resulting mixture of steam and the volatile organic compound is condensed and collected in a receiver.

(A) In thin layer chromatography $(TLC)$,the stationary phase (silica gel) is polar in nature.
The $R_f$ value is inversely proportional to the polarity of the compound.
Non-polar compounds interact less with the polar stationary phase and move faster with the non-polar solvent,resulting in a higher $R_f$ value.
Comparing the polarities:
$1$. $N$-methylpyridinium ion is an ionic species,making it the most polar.
$2$. Phenol has an $-OH$ group,allowing for hydrogen bonding,making it polar.
$3$. Pyridine is polar due to the lone pair on nitrogen.
$4$. Propylbenzene is a hydrocarbon and is the least polar among the given options.
Therefore,propylbenzene will have the highest $R_f$ value.

(B) The correct matches are:
$A$. $CHCl_3 + C_6H_5NH_2$ (Chloroform and Aniline) are separated by $III$. Distillation due to difference in boiling points.
$B$. $C_6H_{14} + C_5H_{12}$ (Hexane and Pentane) are separated by $IV$. Fractional distillation as they are miscible liquids with close boiling points.
$C$. $C_6H_5NH_2 + H_2O$ (Aniline and Water) are separated by $I$. Steam distillation.
$D$. Organic compound in $H_2O$ is separated by $II$. Differential extraction (solvent extraction).
Therefore,the correct sequence is $A-III, B-IV, C-I, D-II$.

(C) . $H_2O / CH_2Cl_2 \rightarrow II$. $CH_2Cl_2$ and $H_2O$ are immiscible liquids with different densities,so they can be separated by differential solvent extraction.
$B$. $\alpha$-tetralone / $p$-nitrophenol $\rightarrow III$. Due to the presence of an $-OH$ group in $p$-nitrophenol,it exhibits hydrogen bonding and has different polarity compared to $\alpha$-tetralone,allowing separation by column chromatography.
$C$. Kerosene / Naphthalene $\rightarrow IV$. Due to the difference in boiling points,they can be separated by fractional distillation.
$D$. $C_6H_{12}O_6 / NaCl \rightarrow I$. $NaCl$ (ionic compound) can be separated from glucose by crystallization based on solubility differences.

(A) In column chromatography,the stationary phase is typically polar (e.g.,silica gel).
The compound that is least polar moves faster and elutes first,while the most polar compound moves slower and elutes last.
Based on the figure,compound '$a$' is at the top,'$b$' is in the middle,and '$c$' is at the bottom (closest to the exit).
Therefore,the order of elution is '$c$' (first),then '$b$',then '$a$' (last).
This implies that '$c$' is the least polar and '$a$' is the most polar.
Let's evaluate the statements:
$A.$ '$c$' is more polar than '$a$' and '$b$': Incorrect,'$c$' is the least polar.
$B.$ '$a$' is least polar: Incorrect,'$a$' is the most polar.
$C.$ '$b$' comes out of the column before '$c$' and after '$a$': Incorrect,'$c$' comes out first,then '$b$',then '$a$.'
$D.$ '$a$' spends more time in the column: Correct,as it is the most polar and interacts most strongly with the stationary phase.
The incorrect statements are $A, B,$ and $C$.

(D) In column chromatography,the compound that elutes first has a weaker interaction with the stationary phase and a higher $R_f$ value.
Conversely,the compound that elutes later has a stronger interaction (adsorption) with the stationary phase and a lower $R_f$ value.
Since '$A$' eluted first,'$B$' must have eluted later.
Therefore,'$B$' has a lower $R_f$ value and stronger adsorption to the stationary phase.
$R_f = \frac{\text{distance covered by substance}}{\text{distance covered by solvent}}$

(A) In thin layer chromatography $(TLC)$,the component that travels the furthest has the highest $R_f$ value,indicating it is the least adsorbed on the stationary phase (silica gel) and has the highest affinity for the mobile phase.
In column chromatography,the component with the highest affinity for the mobile phase elutes first.
Based on the provided $TLC$ plate,the order of distance traveled is $A > C > B$.
Therefore,the order of elution (from first to last) is $A, C, B$.

(B) In thin layer chromatography $(TLC)$,the stationary phase is polar (silica gel) and the mobile phase is non-polar (hexane).
Compounds that are more polar interact more strongly with the stationary phase and travel a shorter distance,resulting in a lower $R_f$ value.
Compounds that are less polar travel a longer distance,resulting in a higher $R_f$ value.
From the figure,the distances traveled by compounds $A$,$B$,and $C$ are $6 \ cm$,$4 \ cm$,and $2 \ cm$ respectively,with the solvent front at $8 \ cm$.
The compound that travels the shortest distance is the most polar.
Thus,compound $C$ is the most polar.
The $R_f$ value for compound $C$ is calculated as:
$R_f = \frac{\text{Distance traveled by compound } C}{\text{Distance traveled by solvent}} = \frac{2 \ cm}{8 \ cm} = 0.25$
Converting this to the required format:
$0.25 = 25 \times 10^{-2}$

(B) In paper chromatography,a special quality paper known as chromatography paper is used.
This paper contains water trapped in its pores,which acts as the stationary phase.

(D) Steam distillation is the technique used for the purification of substances that are steam volatile and immiscible with water.
In this process,the substance is heated by passing steam through it,which carries the volatile component along with it,leaving behind non-volatile impurities.

(C) The principle of differential adsorption is the basis for adsorption chromatography.
$1$. Column chromatography is a type of adsorption chromatography where the stationary phase is a solid adsorbent.
$2$. Thin layer chromatography $(TLC)$ is also a type of adsorption chromatography where a thin layer of adsorbent is coated on a glass or plastic plate.
$3$. Paper chromatography is primarily based on the principle of partition chromatography,where the stationary phase is water trapped in the cellulose fibers of the paper.
Therefore,both Column chromatography $(A)$ and Thin layer chromatography $(B)$ are based on differential adsorption.