Tag: what floats - what sinks

Questions Related to what floats - what sinks

Both temporary and permanent hardness in water is removed by:

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

  1. boiling

  2. filtration

  3. distillation

  4. decantation

Show answer
Correct Option: C
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.

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

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

  1. $Ca(OH) _{2}$

  2. $Na _{2}CO _{3}$

  3. $CaCO _{3}$

  4. $CaO$

Show answer
Correct Option: B
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. $CaCl _2+Na _2CO _3 \rightarrow CaCO _3 \downarrow + 2 NaCl$

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

  1. boiling

  2. filtration

  3. distillation

  4. decantation

Show answer
Correct Option: C
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.

Hard water can be used:

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

  1. in boilers

  2. in textile industry

  3. in paper industry

  4. in drinking

Show answer
Correct Option: D

Calgon is an industrial name given to____________.

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

  1. normal sodium phosphate

  2. sodium meta-aluminate

  3. sodium hexametaphosphate

  4. hydrated sodium aluminium silicate

Show answer
Correct Option: C
Explanation:

Calgon is an industrial name given to sodium hexametaphosphate. Its formula is $Na _{2}[Na _{4}(PO _{3}) _{6}]$.

Temporary hardness of water can be removed by :

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

  1. boiling

  2. saponification

  3. clark's method

  4. chlorination

Show answer
Correct Option: A,C
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.
$Ca(HCO _3) _2+Ca(OH) _2 \rightarrow 2CaCO _3+2H _2O$.

The exhausted permutit is regenerated by treating sodium hydroxide solution in Clark's method for removing permanent hardness.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Yes the exhausted permutit is regenerated by treating sodium hydroxide solution in Clark's method for removing permanent hardness.

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

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

  1. True

  2. False

Show answer
Correct Option: A
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.

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

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

  1. $0^oC$

  2. $4^oC$

  3. $40^oC$

  4. $100^oC$

Show answer
Correct Option: B
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.

Calgon is an artificial zeolite for removing permanent hardness.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Calgon is an artificial zeolite, zeolites contains Na and Al which softens the hard water.

hence, calgon is used for removing permanent hardness.