Tag: evs

Questions Related to evs

Which of the following is/are soluble in water?

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

  1. Ghee

  2. Curd

  3. Blood

  4. Sugar

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Correct Option: C,D
Explanation:
Sucrose or sugar is a polar compound which can break the H-bond present in water due to this reason sugar can dissolve in water . 
Blood is a colloid or suspension composing red blood cells floating in a liquid plasma.If we add it to water, the plasma disperses in the water, becoming more dilute.
Oil and ghee are non-polar in nature as a result they can't interact with a polar solvent like water hence they are insoluble in water.

Which of the following is denser than water?

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

  1. Wooden plank

  2. Buttons

  3. Nails

  4. Paper

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Correct Option: B,C
Explanation:
The density of nail (as of iron) is much larger than the water. So it sinks easily.
The button is more dense than the water and sinks in water.

Chemically calgon is:

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

  1. sodium aluminosilicate

  2. sodium sulphate

  3. sodium hexa meta phosphate

  4. alkyl sulphonic acid

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Correct Option: C
Explanation:

Calgon is a trade name of a complex salt, sodium hexametaphosphate $(NaPO _3) _6$.

Which of the following substance is not present in clear water?

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

  1. $Ca\left ( HCO _{3} \right ) _{2}$

  2. $MgCl _{2}$

  3. $CaSO _{4}$

  4. $CaCO _{3}$

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Correct Option: D
Explanation:

$CaCO _3$ is not present in the clear water. It attains the temporary hardness to the water.

Identify the substance that is not a water softener.

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

  1. $NaOH$

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

  3. $Na _{2}Al _{2}Si _{2}O _{8}$

  4. $MgCl _{2}$

Show answer
Correct Option: D
Explanation:

The substance that is not a water softener $MgCl _2$, which is responsible for permanent hardness of water.


Other compounds are used for softening of water.

Option D is correct.

............ process is used for the removal of hardness of water.

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

  1. Calgon

  2. Baeyer

  3. Serpeck

  4. Hoope

Show answer
Correct Option: A
Explanation:
Calgon process is used for the removal of hardness of water. 

Calgon is a trade name of a complex salt, sodium hexametaphosphate $(NaPO _3) _6$. 

It is used for softening hard water.

Option A is correct.

Hard water can be softened in ?

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

  1. A chromatograph

  2. An ion exchanger

  3. A calorimeter

  4. An earthenware pot

Show answer
Correct Option: B
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.

Sodium hexa-metaphosphate is known as:

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

  1. calgon

  2. permutit

  3. natalite

  4. nitrolim

Show answer
Correct Option: A
Explanation:

Sodium hexametaphosphate $(NaPO _3) _6$, is known as calgon.

It is used for softening hard water.

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

  1. True

  2. False

Show answer
Correct Option: B
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.

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 $Ca{CO} _{3}$ :

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

  1. $2$ ppm

  2. $3$ ppm

  3. $4$ ppm

  4. $6$ ppm

Show answer
Correct Option: D
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=$6$ $ppm$