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

Both temporary and permanent hardness in water is removed by:

  1. boiling

  2. filtration

  3. distillation

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

Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. Permenant hardnesscan be removed by: (1) adding washing soda, (2) permutit method (3) by using ion exchange resins.

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

Both temporary and permanent hardness is removed on boiling water with :-

  1. $Ca(OH) _{2}$
  2. $Na _{2}CO _{3}$
  3. $CaCO _{3}$
  4. $CaO$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Temporary hardness is removed by boiling water with $NaOH$ and $Na _2CO _3$. $Ca(HCO _3 ) _2+2NaOH \rightarrow CaCO _3 \downarrow +Na _2CO _3+2H _2O$ Permanent hardness is removed by boiling water with sodium carbonate. $CaCl _2+Na _2CO _3 \rightarrow CaCO _3 \downarrow + 2 NaCl$

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks
Both temporary and permanent hardness in water is removed by________.

  1. boiling

  2. filtration

  3. distillation

  4. decantation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. permanent hydration can be removed by adding washing soda, permutit method and by using ion exchange resins.
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. boiling

  2. saponification

  3. clark's method

  4. chlorination
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

The temporary hardness of water can be removed by boiling. $Ca(HCO _3) _2 \xrightarrow {boil} CaCO _3 \downarrow + CO _2 \uparrow + H _2O$.

Clark's method which uses lime (calcium hydroxide), it is also used for removal of temporary hardness of water.
$Ca(HCO _3) _2+Ca(OH) _2 \rightarrow 2CaCO _3+2H _2O$.

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

Calgon removes hardness by forming complex compounds with the $Ca^{2+}$and $Mg^{2+}$ ions of hard water or by adsorption.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Calgon is $(Na _6P _6O _{18})$ i.e. sodium hexa-metaphosphate. The calgon when added to hard water forms a  soluble complex.


$Na _2[Na _4(PO _3) _6]+2CaSO _4\longrightarrow 2Na _2SO _4+Na _2[Ca _2(PO _3) _6]$ soluble

In the same way, $Mg^{2+}$ can also precipitate as $Na _2[Mg _2(PO _3) _6]$ and water becomes free from $Mg^{2+}$ and $Ca^{2+}$ ions.

Thus the answer is True.

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

The density of water is not same at all temperatures because of its anomalous expansion. The density is maximum at:

  1. $0^oC$
  2. $4^oC$
  3. $40^oC$
  4. $100^oC$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Due to anomalous expansion of water the density of water is not same at all temperatures. When water is cooled from room temperature it first contracts in volume and becomes increasingly dense as do other liquids but at $4^oC$ water reaches maximum density.