Tag: what floats - what sinks

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Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Hard water can be softened in ?

  1. A chromatograph

  2. An ion exchanger

  3. A calorimeter

  4. An earthenware pot
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer:- (B) An ion exchanger

Explanation:-
In ion exchanger, the hard water is softened because it no longer contains calcium or magnesium ions. Ion exchange units that replaces calcium and magnesium ions from water are known as water softeners.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks
Water which doesn't give lather immediately with soap is called soft water.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Soaps are basically sodium salt of fatty acids. 

In the presence of excess calcium and magnesium ions in water, the sodium ions are replaced by these ions and are precipitated as scum. 

Water containing an excess of these (calcium and magnesium) ions is called hard water.

Therefore option $B$ is correct.
Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

One litre of a sample of hard water contain $4.44mg$ $Ca{Cl} _{2}$ and $1.9mg$ of $Mg{Cl} _{2}$, what is the total hardness in terms of ppm of $Ca{CO} _{3}$ :

  1. $2$ ppm
  2. $3$ ppm
  3. $4$ ppm
  4. $6$ ppm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$1$ mole $CaCl _2\equiv 1$ mole $CaCO _3\equiv 1$ mole $MgCl _2$

$\therefore 100g$ $CaCO _3$ produces $111g$ of $CaCl _2$
$\therefore 4.44mg$ $CaCl _2$ produces $\cfrac {4.44\times 100}{111}mg$ $CaCO _3$
Similarly, $100g$ $CaCO _3$ is required for $95g$ $MgCl _2$
$\therefore 1.9mg$ $MgCl _2=\cfrac {1.9\times 100}{95}mg$ $CaCO _3$
                               $=2mg$ $CaCO _3$
Total hardness= Hardness due to $CaCl _2$+Hardness due to $MgCl _2$
                         =$4+2$
Total hardness=$6$ $ppm$

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Temporary hardness can be removed by:

  1. boiling

  2. clark's process

  3. calgon's process

  4. permutit method
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

By boiling : - On boiling, soluble $Mg{ \left( HC{ O } _{ 3 } \right)  } _{ 2 }$ is converted to insoluble $Mg{ \left( OH \right)  } _{ 2 }$ and $Ca{ \left( H{ CO } _{ 3 } \right)  } _{ 2 }$ to insoluble ${ CaCO } _{ 3 }$. It is because high solubility of $Mg{ \left( OH \right)  } _{ 2 }$ as compared to $Mg{ CO } _{ 3 }$, than $Mg{ \left( OH \right)  } _{ 2 }$ is precipitated. Precipitates can be removed by filtration.


By Clark's Method : Calculated amount of lime is added to hard water $\rightarrow Ca{ CO } _{ 3 }$ precipitates out & $Mg{ \left( OH \right)  } _{ 2 }$ can be filtered off.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Permanent hardness of water can be removed by:

  1. permutit process

  2. boiling

  3. ion-exchange

  4. calgon's process
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

Permanent hardness of water can be removed by permutit process. Permutite is an artifical zeolite used for softening of water. Through ion-exchange process, here cation-anion exchange chamber is used to obtain pure water. In calgon's process sodium hexa meta phosphate is used to soften the water.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Hard water causes _________ .

  1. burning of skin

  2. scales on the boiler walls

  3. relief to the body

  4. head-ache
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Hard water contains minerals specifically $Ca,Mg$ and $Fe$ which can dry our skin and cause flaking and itching.

The presence of these minerals also causes scaling in boiler walls as these minerals are less soluble in hot than cold or to the presence of too high concentration of silica in relation to the alkalinity of water in the boiler.