Practice Questions of Distillation with Answer & Explanations

Distillation is an essential industrial technique utilized for the purification of various substances. This process involves the selective boiling and subsequent condensation to effectively isolate individual components or compounds from a liquid mixture.

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The distillation process can achieve nearly complete separation (producing almost pure components) or a partial separation (resulting in a higher concentration of specific components within the mixture). The methodology is based on variances in the relative volatility of the mixture’s constituents in different scenarios. While distillation serves as a critical operation across various industrial sectors, it is fundamentally a physical separation process and not a chemical alteration.

Chemistry of Distillation: Questions and Answers

Q1: Porcelain pieces are added to the distillation flask to prevent ____________

a) Overheating

b) Bumping of the solution

c) Uniform boiling

d) None of the mentioned options

Answer: b) Bumping of the solution

Explanation: The introduction of porcelain fragments into the distillation flask is intended to inhibit bumping, which can occur due to inconsistent heating.

Q2: What are the two fundamental processes involved in distillation?

a) Distillation and cooling reflux

b) Distillation and freezing

c) Freezing and cooling reflux

d) Only cooling reflux

Answer: a) Distillation and cooling reflux

Explanation: Distillation encompasses a two-stage process that integrates both distillation and cooling reflux. In a distillation column, gas-liquid two-phase flow is typically executed through countercurrent contact.

Q3: What technique can be used to separate aniline from chloroform?

a) Sublimation

b) Condensation

c) Distillation

d) Evaporation

Answer: c) Distillation

Explanation: The distillation method is effective in separating aniline and chloroform. Aniline (C6H5NH2) is a toxic organic compound, while chloroform (CHCl3) is a colorless liquid with a sweet smell, commonly utilized in the production of refrigerants and PTFE.

Q4: Which of the following substances cannot be separated through distillation?

a) Acetone and water

b) Milk and water

c) Sea water impurities

d) Aniline and chloroform.

Answer: c) Sea water impurities

Explanation: Distillation is not capable of effectively separating milk from water, although it can suitably isolate the other substances listed.

Q5: Distillation is applied to liquids that exhibit ____________

a) A significant difference in their solubility

b) A notable difference in their melting point

c) A considerable difference in their boiling point

d) None of the above

Answer: c) A considerable difference in their boiling point

Explanation: The distillation technique is utilized for liquids that possess a marked difference in boiling points, enabling the separation of air components as well.

Q6: Which salt results from the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), and what method should be employed to isolate it from the solution?

Answer:

The reaction between HCl and NaOH produces sodium chloride (NaCl). Here is the reaction represented:

HCl + NaOH → NaCl + H2O

The extraction of the salt from the solution can be achieved through the distillation process.

Q7: Sketch a labeled schematic illustrating the distillation process.

Answer:

The distillation process is visually represented in the diagram provided below.

Q8: Pair the terms as follows:

Answer:

(a) Melting point → 4. Transition from solid to liquid.

(b) Boiling point → 3. Transition of liquid into gas.

(c) Fractional distillation → 2. Extracting diesel from crude oil.

(d) Distillation → 1. Isolating common salt from a water mix.

Q9: Respond to the queries below:

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1. What method is used to determine the boiling point of water?
2. What visible changes occur in a candle after igniting it?
3. Can a solid and a liquid be separated from a solution using distillation?

Answer:

1. To ascertain the boiling point of water, we will employ the following apparatus:

Experiment: Water is placed in a round-bottom flask fitted with a rubber stopper that has a single hole. A thermometer is inserted into the opening, and we begin heating the flask by positioning it on iron gauze atop a tripod stand.

Observation: The thermometer's temperature will rise. When the mercury level reaches 100°C, boiling initiates, followed by a temperature drop.

Conclusion: The boiling point of water is defined as the juncture where the temperature ceases to rise and boiling commences, marking it at 100°C.

1. Upon lighting the candle, the following transformations occur:

(i) Phase Change: The wax of the candle transitions to a liquid and eventually vaporizes, forming wax vapors.

(ii) Combustion: The burning of wax vapors generates heat and light.

1. Yes, distillation effectively separates the components of a solution composed of a nonvolatile solid (solute) and a liquid (solvent).

Q10: Distillation versus fractional distillation: what are the distinctions?

Answer:

The comparison below outlines the differences between these two processes:

Q11: Highlight the diverse applications of distillation.

Answer:

Distillation serves numerous purposes, including:

• Facilitating laboratory experiments, providing foundational data for chemical and pharmaceutical studies.
• Purifying water by eliminating numerous impurities, a process used in desalination for obtaining clean water. Parents commonly use distilled water in baby food preparations.
• Creating ethyl alcohol through the distillation of fermented materials, which aids in the production of alcoholic beverages.
• Separating various compounds during crude oil distillation, yielding products like gasoline, wax, fuel oil, and lubricants at distinct boiling points.
• Extracting essential oils and fragrances from botanicals, with steam distillation favored to prevent the degradation of plant material.
• Generating flavors for food through steam distillation, evident in citrus oil extraction.
• Employing fractional distillation for the separation of acetone and methyl alcohol.
• Utilizing cryogenic distillation to isolate gases like oxygen, nitrogen, carbon dioxide, and argon from the atmosphere.
• Concentrating sugarcane juice in the sugarcane industry with the vacuum distillation technique.

Q12: Fractional distillation facilitates the separation of miscible liquids with a boiling point difference of less than 25 K. What component of the fractional distillation apparatus enhances its efficiency relative to standard distillation? Include a diagram for clarity.

Answer:

Fractional Distillation of Miscible Liquids:

• Utilizing a fractionating column greatly enhances the efficiency of fractional distillation compared to simple distillation by optimizing liquid condensation potential.
• A fractionating column outfitted with glass beads or helices increases the surface area for vapor collision, facilitating energy loss, leading to rapid condensation and effective distillation.
• Lengthening the fractionating column can further boost efficiency.

Q13: In reference to Fig. 2.1 (a) and (b), which tube will function more effectively as a condenser in the distillation apparatus?

Answer:

Tube (a) is deemed more efficient as a condenser due to the inclusion of marbles, which augment the vapor contact area. This augmentation allows the vapors additional time to condense, rendering the first column superior to the second without marbles.

Q14: Provide examples of mixtures that possess the following characteristics. Suggest an appropriate method to separate these mixture components:

a) A volatile and a non-volatile component.

b) Two volatile components with noticeable boiling point differences.

c) Two immiscible liquids.

d) Two or more colored constituents dissolvable in certain solvents.

Answer:

(a) Example: Mixture of acetone and water.

A mixture containing a volatile and a non-volatile component can be separated via simple distillation.

(b) Example: Mixture of kerosene and petrol.

Simple distillation can efficiently separate two volatile components with significant boiling point disparities.

(c) Example: Mixture of mustard oil and water.

A separating funnel is employed to isolate a blend of immiscible liquids.

(d) Example: An extract from flower petals containing various pigments.

Chromatography can separate different compounds present in the same solution.

Q15: Briefly explain vacuum distillation.

Answer:

• Vacuum distillation is particularly effective for separating mixtures of liquids with exceptionally high boiling points.
• Heated substances at high temperatures often prove inefficient for vaporization. Thus, ambient pressure is reduced.
• Lowered pressure allows components to vaporize at diminished temperatures, resulting from vapor pressure equilibrium with environmental pressure.
• The produced vapors are condensed, and the resultant distillate can be collected. Additionally, this method yields high-purity samples of substances that may degrade under high temperatures.

Proficiency Questions on Distillation

Q1: Which are the fundamental methods of distillation?

a) Fractional distillation and simple distillation

b) Steam distillation and destructive distillation

c) Steam distillation, simple distillation, and gas distillation

d) Fractional distillation, destructive distillation, and simple distillation

Q2: Define the following terminologies:

(a) Melting point

(b) Boiling point

(c) Distillation.

Q3: Provide scientific reasoning for the following:

(a) A condenser is equipped with two taps.

(b) Upon dawn in winter, dewdrops appear on leaves.

Q4: It is commonly known that salt can be distilled from seawater. However, such a method is not typically regulated for drinking water extraction. What do you suppose is the justification for this?

Q5: You are presented with two water samples labeled ‘A’ and ‘B’. Sample 'A' boils at 100°C, and sample 'B' at 102°C. Which water sample is more likely to remain unfrozen at 0°C? Please elaborate.

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