Tag: chemistry

Questions Related to chemistry

The crystalline salt ${ Na } _{ 2 }{ SO } _{ 4 }.x{ H } _{ 2 }O$ on heating loses 55.9% of its mass. The formula of crystalline salt is:

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. ${ Na } _{ 2 }{ SO } _{ 4 }.5{ H } _{ 2 }O$

  2. ${ Na } _{ 2 }{ SO } _{ 4 }.7{ H } _{ 2 }O$

  3. ${ Na } _{ 2 }{ SO } _{ 4 }.2{ H } _{ 2 }O$

  4. ${ Na } _{ 2 }{ SO } _{ 4 }.10{ H } _{ 2 }O$

  5. ${ Na } _{ 2 }{ SO } _{ 4 }.6{ H } _{ 2 }O$

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Correct Option: D

In which of the following molecules can we calculate crystallization of water ?

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. $CaS{O _4}.2{H _2}O$

  2. ${H _2}S{O _4}$

  3. ${C _2}{H _2}{O _4}.2{H _2}O$

  4. $FeS{O _4}.7{H _2}O$

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Correct Option: B

State whether the given statement is true or false:

Water of crystallization is the water that occurs inside crystals.

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. True

  2. False

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Correct Option: A
Explanation:

Water of crystallization or water of hydration is water that occurs inside the crystals. It refers to water that is found in the crystalline framework of a metal or a salt that is not directly bonded to the metal cation.

In $FeSO _4$.$7H _2O$, $H _2O$ represents:

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. molar mass

  2. molecular weight

  3. molar weight

  4. water of crystallisation

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Correct Option: D
Explanation:

Water of crystallization or water of hydration is the water present inside the crystal. Solids are purified by the procedure called as crystallization in which after purification some pure form of water trap down inside the crystal called as water of crystallization.

The number of molecules of water of crystallisation present in one molecule of ferrous sulphate is_______.

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. $5$

  2. $7$

  3. $6$

  4. $10$

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Correct Option: B
Explanation:

When water is used in the formation of crystals knows as water of crystallization. 'OR' 

Water of crystallization is the total weight of water in a substance at a given temperature and is mostly present in a definite ratio. 
On heating, iron(II) sulfate first loses its water of crystallization and the original green crystals are converted into a brown-colored anhydrous solid. 


$FeSO _4.7H _2O$ the heptahydrate in solution (water as solvent) transforms to both heptahydrate and tetrahydrate when the temperature reaches $56.6 ^\circ C$.


Hence, option $B$ is correct.

The definite number of water molecules which enters into a chemical combination with the substance when the substance is crystallized from its hot saturated solution is called ________. 

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. crystallization

  2. water of crystallization

  3. formation of water molecule

  4. none of the above

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Correct Option: B
Explanation:

The definite number of water molecules which enters into a chemical combination with the substance when the substance is crystallized from its hot saturated solution is called water of crystallization.

A salt associated with water of crystallization is known as a:

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. acid

  2. buffer

  3. hydrate

  4. anion

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Correct Option: C
Explanation:

A salt associated with the water of crystallization is known as a hydrate. The structure of hydrates can be quite elaborate, because of the existence of hydrogen bonds that define polymeric structures.


Hence, the correct option is $\text{C}$

Water of crystallization is present in a definite :

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. shape

  2. ratio

  3. volume

  4. size

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Correct Option: B
Explanation:

Water of crystallization or water of hydration or crystallization water is water that occurs inside crystals. Water is often necessary for the formation of crystals. Water of crystallization is the total weight of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio.

Heated calcium sulphate with half a water of crystallization is commonly called as :

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. washing soda

  2. plaster of paris

  3. naushadar salt

  4. bleaching powder

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Correct Option: B
Explanation:

Plaster of paris which is chemically called calcium sulphate hemihydrate. Since, it is brought to use from paris, called as "plaster of paris". It is prepared by heating of gypsum at 373K. 

Since there are 10 water molecules in washing soda, hence it is known as:

chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

  1. sodium bicarbonate decahydrate

  2. sodium carbonate decahydrate

  3. sodium bicarbonate nanohydrate

  4. sodium decahydrate

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Correct Option: B
Explanation:

Washing soda is called sodium carbonate. Since, there are $10$ water molecules in washing soda, hence it is known as sodium carbonate decahydrate.