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

Calgon used as water softner is:

  1. $Na _2[Na _4(PO _3) _6]$
  2. $Na _4[Na _2(PO _3) _6] $
  3. $Na _2[Na _4(PO _4) _5]$

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

Calgon $\rightarrow { Na } _{ 6 }{ P } _{ 6 }{ O } _{ 18 }\rightarrow { Na } _{ 2 }\left[ { Na } _{ 4 }{ \left( { PO } _{ 3 } \right)  } _{ 6 } \right] $ it is used as water softener, when added to hard water following reaction takes place :

${ Na } _{ 6 }{ P } _{ 6 }{ O } _{ 18 }\rightarrow { 2Na }^{ + }+{ Na } _{ 4 }{ P } _{ 6 }{ O } _{ 18 }^{ 2- }$
${ Ca }^{ 2+ }+{ Na } _{ 4 }{ P } _{ 6 }{ O } _{ 18 }^{ 2- }\rightarrow { \left[ { Na } _{ 2 }{ Ca }{ P } _{ 6 }{ O } _{ 18 } \right]  }^{ 2- }+{ 2Na }^{ + }$

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

In permanent hardness of water, when washing soda is treated with water, ________ is precipitated out.

  1. sodium carbonate

  2. magnesium carbonate

  3. calcium carbonate
  4. $Na _2CO _3 and\ MgCO _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble product.

calcium ions + sodium carbonate → calcium carbonate + sodium ions

$Ca^{+2} + Na _2CO _3\rightarrow CaCO _3 + 2Na^+$

The water is softened because it no longer contains dissolved calcium ions and magnesium ions, hence we can say that it is converted in soft water. It will now form lather  easily with soap.

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

Hard water is unfit for laundries because:

  1. consumes much soap
  2. leaves dirty strains of '$Ca$' and '$Mg$'

  3. causes irritation on skin

  4. water is very hard to handle
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Hard water is unfit for laundries because it can not form lather with soap, hence consumption of soap increases and it leaves dirty strains of calcium and magnesium.