Tag: chemistry

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Questions Related to chemistry

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Copper sulphate crystals are of which color after purification?

  1. White

  2. Black

  3. Blue

  4. Yellow
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To crystallise copper sulphate, it is dissolved in water and a small quantity of dilute sulphuric acid is added to prevent the hydrolysis of copper sulphte. The impurities left behind in the solution are removed by filtration. The filtrate is concentrated to the crystallisation point and then cooled. On cooling, transparent blue crystals of copper sulphate separate.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

When are the crystals of copper sulphate obtained?

  1. when hot acidic copper sulphate solution is cooled gradually.

  2. when cold acidic copper sulphate solution is heated gradually.

  3. when hot acidic copper sulphate solution is cooled suddenly.

  4. when cold acidic copper sulphate solution is heated suddenly
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When hot acidic $ copper : sulphate$ solution is cooled gradually, the crystals of  $ copper : sulphate$ are obtained.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Which method is used to separate diastereomers?

  1. Distillation

  2. Fractional Crystallisation

  3. Sublimation

  4. Evaporation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Diastereomers have different physical properties. You can separate them by ordinary separation techniques such as fractional crystallization. 


Then you treat the separated diastereomers with appropriate reagents to regenerate the original enantiomers.

Option B is correct.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

The method by which common salt is obtained from concentrated seawater is called:

  1. Crystallisation

  2. Catalyst

  3. Hydrolysis

  4. Evaporation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The method by which common salt is obtained from concentrated seawater is called crystallisation.


Crystallisation is a technique used to separate a solid from a solution. The solid is more soluble at a higher temperature and less soluble at a lower temperature.

Hence, option A is correct.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

The crystals that are obtained after crystallization are:

  1. more than 90% pure

  2. between 40% and 80% pure

  3. between 10% to 40% pure

  4. 10% pure
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Crystal is the pureset form of a compound, the method of forming crystals is known as crystallization, crystals are more than 90% pure and its purity can be increased upto 99.9% by recrystallization technique.  

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Why crystallisation is used for obtaining pure copper sulphate from an impure sample rather than simple evaporation?

  1. Some impurities may remain dissolved in the solution even after filtration. On evaporation, these may contaminate the solid

  2. Because crystallisation is comparatively easier than evaporation

  3. Because crystallisation is comparatively faster

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Crystallisation technique is better than simple evaporation technique as some solids decompose and some impurities may remain dissolved in the solution even after filtration. On evaporation, these contaminate the solid.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Crystals of pure copper sulphate are separated from the solution by :

  1. condenstaion

  2. distillation

  3. solidification

  4. filtration
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pure copper sulphate can be obtained from an impure sample by re-crystallization. The impure sample is dissolved in water, heated and then cooled which then later forms crystals. These copper sulphate crystals are then separated by filtration and drying.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Which of the following method is used for water treatment?

  1. Centrifugation

  2. Sedimentation

  3. Evaporation

  4. Crystallization
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Crystallization is a process of :

  1. cooling a hot concentrated solution of a substance to obtain beads

  2. cooling a hot concentrated solution of a substance to obtain crystals

  3. heating a solution to obtain beads

  4. all of above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Crystallization is a process of cooling a hot, concentrated solution of a substance to obtain crystals. It is used to obtain pure solid from impure sample.