To separate mixtures into their constituent elements and/or compounds, separation techniques are used. A mixture is made up of elements and/or compounds that have not been chemically combined together. By separating the constituents of mixtures, we can learn about the properties of known/unknown substances in mixtures and potentially use them to make useful substances like medicines.
We can select the most appropriate separation technique to isolate the substances in the mixture based on their physical and chemical properties.
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Definition: A separation is a process that divides a chemical mixture or solution into two or more distinct product mixtures. A separation process may completely separate a mixture into its pure constituents in certain cases. Separations take advantage of differences in chemical or physical properties. For example, size, shape, mass, density, or chemical affinity between mixture constituents. |
Separation Techniques Chemistry Questions with Solutions
Q1. Which of the following methods can be used to separate a mixture of iron and copper fillings?
a.) Magnetic separation
b.) Crystallisation
c.) Evaporation
d.) Distillation
Correct Answer – (a.) Magnetic separation
Q2. Which of the following is a method of separation used to separate a mixture that comprises solutes that dissolve in the same solvent?
a.) Evaporation
b.) Filtration
c.) Chromatography
d.) Sublimation
Correct Answer – (c.) Chromatography.
Q3. A mixture of oil and water is separated by ____.
a.) Separating funnel
b.) Evaporation
c.) Decantation
d.) Filtration
Correct Answer – (a.) Separating funnel.
Q4. Which method of separation will be used to separate butter from curd?
a.) Sublimation
b.) Chromatography
c.) Centrifugation
d.) All of the above
Correct Answer – (c.) Centrifugation.
Q5. The process in which the heavier impurities settle at the bottom is ____.
a.) Decantation
b.) Sedimentation
c.) Filtration
d.) Evaporation
Correct Answer – (b.) Sedimentation.
Q6. What are physical methods of separation?
Answer: Methods that use differences in physical properties to separate the components of a mixture, such as handpicking, threshing, winnowing, sieving, evaporation, distillation, filtration, and chromatography, can be used to physically separate the components of a mixture.
Q7. List the methods of separation that can be used to separate the mixtures of solids and liquids.
Answer: The methods of separation used to separate the mixtures of solids and liquids are as follows:
- Filtration
- Crystallisation
- Centrifugation
- Chromatography
- Evaporation
- Distillation
Q8. Which separation method would be most effective on the following mixtures?
a.) Vinegar (acetic acid (liquid) solution in water).
b.) Tea with loose tea leaves.
c.) Solid copper sulphate in water.
Answer:
a.) Vinegar (acetic acid (liquid) solution in water) – Distillation.
b.) Tea with loose tea leaves – Filtration.
c.) Solid copper sulphate in water – Evaporation.
Q9. What is the difference between distillation and fractional distillation?
Answer: The difference between distillation and fractional distillation are as follows:
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Distillation |
Fractional Distillation |
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Distillation is a method of separating liquids with differences in boiling points of more than 25℃. |
Fractional distillation is a method of separating liquids with differences in the boiling point of less than 25℃. |
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A simple apparatus with two simple flasks and a condenser is required for the experiment. |
A complex apparatus with a fractionating column is required for the experiment. |
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Every step of the vaporisation-condensation process is recognised as simple distillation. |
Multiple simple distillation processes with low losses are carried out in a fractional distillation apparatus. |
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The distillation method, for example, can be used to separate water from seawater. |
The fractional distillation method, for example, can separate an ethanol-water mixture. |
Q10. Describe the method to separate a mixture of sand and salt.
Answer: We can separate the mixture of salt and sand by using the method of filtration, evaporation and condensation.
The steps to separate the mixture are as follows:
- Keep the sand and salt mixture in a beaker and add some water to it.
- Leave the beaker aside for a while. The sand will settle at the bottom, and salt will dissolve in the water.
- The water on top can be poured into a different beaker, and the sand can be separated by filtration.
- Heat the beaker containing salt water for a few minutes.
- The vapours can be collected and condensed, giving us salt crystals.
Q11. Which method is used to separate the mixture of camphor and sand?
Answer: Camphor is a sublime substance, whereas sand is not. Therefore, the mixture of camphor and sand can be separated by using the method of sublimation.
The process involves slowly heating the mixture where the sand will remain in the container, but camphor will vaporise. The camphor vapours are then collected and condensed where the solid camphor crystallises.
Q12. Which method can be used to separate a mixture of two solids?
Answer: All mixtures of two solid substances can be separated using:
- Using a suitable solvent
- Through sublimation
- Using a magnet
i.) Using a suitable solvent:
One constituent of a mixture is soluble in a specific liquid solvent, while the other is insoluble.
Differences in the solubilities of a mixture’s constituents can be used to separate them.
ii.) Through sublimation:
Sublimation is the process of conversion of a solid state into vapours on heating and vapours into solids on cooling. The solid substance that sublimates is known as sublime. Sublimate is the solid substance formed by cooling the vapours.
Sublimation is a process that separates substances from a mixture that sublimes due to heating.
iii.) Using a magnet:
A magnet can be used to separate a mixture that contains iron as one of its constituents.
Q13. Write a short note on the following:
a.) Centrifugation
b.) Sedimentation and decantation
Answer:
a.) Centrifugation – This method is used to separate out tiny solid particles that normally pass through filter paper, and thus the separation of these insoluble particles is accomplished through centrifugation. The centrifugation process is determined by particle shape and size, medium viscosity, and rotational speed. We can separate butter from cream using this method. We use a centrifuge, which includes a centrifuge tube holder that holds an equal amount of solid-liquid mixture. When the rotor is rotated, the denser insoluble particles separate from the liquid and settle at the bottom of the tube, while the liquid collects at the top due to centrifugal force.
b.) Sedimentation and decantation – Sedimentation is defined as the process by which solids are separated from liquids. All of the solids settle to the bottom of the beaker, leaving a clear layer of liquid on top. Sedimentation is the process by which heavier impurities in a liquid, typically water, settle to the bottom of the container containing the mixture. It takes some time to complete the process.
Example – This method is used by water treatment plants to filter out unwanted particles from dirty water.
Decantation is defined as a separation process that separates two immiscible liquids. Pour out the clear upper layer of liquid to accomplish this. Decantation is the separation of an oil mixture from water.
Example – This method separates two non-mixing liquids, such as oil and water.
Q14. How can you separate two immiscible liquids?
Answer: Two immiscible liquids can be separated by the separating funnel method. The mechanism involves taking advantage of the particles’ unequal density in the mixture. Using this technique, oil and water can be easily separated. The two liquids are placed in the funnel and allowed to settle out and form two layers for a short period of time. The funnel’s tap is opened, allowing the bottom liquid to flow. The two liquids are now distinct.
Q15. Describe the method of fractional distillation.
Answer: Fractional distillation is a type of distillation that involves the separation of miscible liquids. This process involves repeated distillations and condensations, and the mixture is usually separated into component parts.
A chemical mixture’s components are separated into different parts (called fractions) based on their different boiling points.
Vapours from a boiling solution are passed through a tall column known as a fractionating column. The column is packed with plastic or glass beads, which provide more surface area for condensation and evaporation. The temperature of the column decreases gradually along its length. Higher boiling point components condense on the column and return to the solution; lower boiling point (more volatile) components pass through the column and are collected near the top.
Practice Questions on Separation Techniques
Q1. Which of the following separation techniques is affected by differences in boiling point?
a.) Evaporation
b.) Sublimation
c.) Distillation
d.) Crystallisation
Q2. Which technique is used to separate drugs from blood?
a.) Sublimation
b.) Chromatography
c.) Centrifugation
d.) Evaporation
Q3. Explain the method of crystallisation.
Q4. How can different gases be separated from the atmosphere?
Q5.What is chromatography?
Click the PDF to check the answers for Practice Questions.
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