Tag: hard and soft water

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

Sodium carbonate softens permanent hard water.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Sodium carbonate, $Na _2CO _3$ is also known as washing soda. It can remove temporary and permanent hardness from water. It is soluble in water and adds a large amount of carbonate ions to the water. These react with dissolved calcium and magnesium ions in the water to produce insoluble precipitates.

Hence, it is a true statement.
Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Temporary hardness of water can be removed by:

  1. filtration

  2. boiling

  3. decantation

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

By boiling, the bicarbonates undergo decomposition to form insoluble carbonates of $Ca/Mg$ which can further be removed by filtration.

$Ca{ \left( { HCO } _{ 3 } \right)  } _{ 2 }\left( aq \right) \rightarrow CaC{ O } _{ 3\left( s \right)  }+{ CO } _{ 2\left( g \right)  }+{ H } _{ 2 }O(l)$
$Mg{ \left( HCO \right)  } _{ 3 }(aq)\rightarrow Mg{ CO } _{ 3\left( s \right)  }+{ CO } _{ 2\left( g \right)  }+{ H } _{ 2 }{ O } _{ (l )}$
Then the water obtained will be free from $Ca$ and $Mg$ ions and is soft.

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

Hardness of water can be removed by :

  1. adding calcium hydroxide

  2. ion-exchange method

  3. both a and b

  4. none of above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hardness of water can be removed by the following two methods:
CLARK'S METHOD 
In Clarks method a calculated amount of calcium hydroxide $Ca (OH) _2$ is added to hard water. Due to reaction, insoluble carbonates are obtained which are separated by filtration.
$Ca(HCO _3) _2 + Ca(OH) _2 2CaCO _3 + 2H _2O$
$Mg(HCO _3) _2 + Ca(OH) _2 CaCO _3 + MgCO _3 + 2H _2O$
ION-EXCHANGE METHOD
In this method sodium zeolite is used as ion-exchanger. Na-zeolite is passed through the pipes containing    hard water. Sodium zeolite is converted into calcium-zeolite or magnesium-zeolite. These are insoluble in water and are separated from water by filtration.
$Ca+2 + Na2-zeolite Ca-zeolite + 2Na+1$
$Mg+2 +Na2-zeolite Mg-zeolite + 2Na+1$

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

Temporal hardness can be removed by just boiling the water because :

  1. Form salts

  2. Converts magnesium to soluble magnesium

  3. Converts carbonate to soluble carbonate

  4. Converts carbonate to insoluble carbonate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Temporal hard water is caused by calcium bicarbonate. This hardness can be removed by just boiling the water, as this converts the carbonate to insoluble carbonate (This leaves a precipitate and can clog your boiler).