Tag: chemistry

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Multiple choice chemistry basic analytical techniques filtration and crystallisation other methods of separation separation techniques

A public health inspector suspects that in addition to two harmless dyes (boiling points $69\ ^oC$ and $71\ ^oC$), a lollipop also contains a poisonous green dye (boiling point $73\ ^oC$). Which of the following can be used to confirm his suspicion?

  1. Fractional distillation

  2. Paper chromatography

  3. Filtration

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

A public health inspector suspects that in addition to two harmless dyes(boiling points 69 C and 71 C), a lollipop also contains a poisonous green dye (boiling point 73 C). Paper chromatography can be used to confirm his suspicion. Here, different dyes will have different affinity for paper (stationary phase) and solvent (mobile phase). Fractional distillation is used when individual components of mixtures have boiling points more than 30 C. Filtration and crystallisation are used in separation / purification of solid from liquid.

Multiple choice chemistry basic analytical techniques filtration and crystallisation other methods of separation separation techniques

John tried to separate sugar from its solution using the evaporation method. However, he was unsuccessful. Which of the following is the likely reason?

  1. There was insufficient sugar in the solution

  2. He had forgotten to stir the solution during heating

  3. The sugar had decomposed

  4. The sugar had vaporised.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
John tried to separate sugar from its solution using the evaporation method. However, he was unsuccessful as the sugar had decomposed. When you sugar (sucrose) is heated, it undergoes dehydration. The crystalline structure breaks down. Molecules decompose into glucose and fructose and then lose water and polymerize to form caramel, which is a red-orange colored solid.
Multiple choice chemistry basic analytical techniques filtration and crystallisation other methods of separation separation techniques

Sand that is needed for a project has some common salt accidentally mixed with it. which of the following processes need to be used to separate sand and salt?
1. Filtration
2. Evaporation
3. Distillation
4. Crystallisation

  1. 1, 2

  2. 1,2 and 4

  3. 1, 2 and 3

  4. 1,2,3 and 4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

To separate the mixture of salt and sand;

first we will make the aqueous solution, salt gets dissolved in water and sand particle remain undissolved,
so, the misture can be separated by filtration and evaporation.

Multiple choice chemistry petrochemicals and polymers food spoilage and food preservation methods of preserving food chemicals in food

Modern oil-based paints contain oils that can dry to form strong, adhesive films by cross-linking of fatty acid chains. Some of these drying oils' are mentioned here. Can you pick the false one?

  1. Linseed oil

  2. Turpentine oil

  3. Soyabean

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

Drying oils are prone to hardening upon exposure to air, due to free radical base polymerization, thus forming a flexible, transparent and waterproof film. This property is exhibited by linseed, turpentine and soybean oils. 

Multiple choice chemistry petrochemicals and polymers food spoilage and food preservation methods of preserving food chemicals in food

________ act as protective agent on the surface of animals and plants.

  1. Carbohydrates

  2. Vitamins

  3. Nucleic Acids

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

Wax act as a protective agent on the surface of animals and plants. It protects animals and plants from excessive loss of moisture. It protects the plants and fruits from becoming infected with fungi and bacteria.


Wax contains esters of long chain fatty acids and long chain alcohols or sterol.

Hence, option D is correct.

Multiple choice chemistry petrochemicals and polymers food spoilage and food preservation methods of preserving food chemicals in food

High molecular weight alcohols are present in:

  1. waxes

  2. fats

  3. oils

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

waxes are monoglycerides, these are form by the condensation reaction between monohydroxy alcohol and fatty acid, this is the high molecular weight compound.

Example- Bee wax 
( Hexacosyl palimitate $\rightarrow$ Hexacosyl alcohol+ Palmitic acid)
$C _{26}H _{53}OH + C _{15}H _{31}COOH \overset{-H _2O}\rightarrow C _{26}H _{53}COOC _{15}H _{31}$ 

Multiple choice chemistry petrochemicals and polymers food spoilage and food preservation methods of preserving food chemicals in food

Four oils $A, B, C$ and $D$ have the following values of melting points.
(a) $258$ K (b) $273$ K (c) $295$ K (d) $303$ K
Among these, which oil is prohibited from consumption by cardiac patients?

  1. a

  2. b

  3. c

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

The oils having higher unsaturation in the fatty acid component have very low melting points. Hence, on the consumption of these oils there is less chance of blockage of blood vessels. The saturated oils have higher melting points and they get solidified easily. Therefore they block the blood vessels and so are prohibited from consumption by cardiac patients. Hence oil D is prohibited from consumption by cardiac patients.

Multiple choice chemistry element, compound and mixture different types of solutions various mixtures introduction to solutions

A concentrated solution contains high amount of ________.

  1. solvent

  2. solute

  3. both solute and solvent

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A concentrated solution contains the maximum amount of solute that can be dissolved because solubility depends on temperature, a solution that is concentrated at one temperature may not be concentrated at a higher temperature.

Multiple choice chemistry element, compound and mixture different types of solutions various mixtures introduction to solutions

Which of the following is used as antifreeze on cars for cooling the engine?

  1. $10\%$ (V/V) ethanol solution in water
  2. $35\%$ (V/V) ethanol solution in glycol
  3. $45\%$ (V/V) ethanol solution in glycol
  4. $20\%$ (V/V) ethanol solution in water
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ethanol-water mixtures are commonly used as antifreeze in cooling systems because they lower the freezing point of the coolant.