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Concentration Terms - An Introduction (w/w etc)

Permanent har...

Question

Permanent hardness is due to $S O_{4}^{2 -}$ and $C l^{-}$ of $C a^{2 +}$ and $M g^{2 +}$ and is removed by the addition of $N a_{2} C O_{3}$ .
$C a S O_{4} + N a_{2} C O_{3} ⟶ C a C O_{3} + N a_{2} S O_{4}$
$C a C l_{2} + N a_{2} C O_{3} ⟶ C a C O_{3} + 2 N a C l$
If hardness is $100$ ppm $C a C O_{3}$ , amount of $N a_{2} C O_{3}$ required to soften $10$ L of hard water is :

A

2.12

g

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B

0.106

g.

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C

10.6

g

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D

1.06

g

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Solution

The correct option is B $1.06$ g
$N a_{2} C O_{3} 106 g = C a C O_{3} 100 g$
$H a r d n e s s i n 10^{6} g H_{2} O = 100 g C a C O_{3}$ .
$∴ H a r d n e s s i n 10 L (10^{4} m L = 10^{4} g) H_{2} O = 1 g C a C O_{3}$ .
$100 g C a C O_{3} r e q u i r e d = 106 g N a_{2} C O_{3}$ .
$∴ 1 g C a C O_{3} r e q u i r e d = 1.06 g N a_{2} C O_{3}$ .

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Similar questions

Q. Permanent hardness is due to

C l^{⊝}

S O_{4}^{2 -}

M g^{2 +}

C a^{2 +}

and is removed by adding

N a_{2} C O_{3}

C a S O_{4} + N a_{2} C O_{3} \to C a C O_{3} + N a_{2} S O_{4}

C a C l_{2} + N a_{2} C O_{3} \to C a C O_{3} + 2 N a C l

Which of the following statements is/are correct?

C a S O_{4}

causes permanent hardness in water. It can be removed by precipitating it as

C a C O_{3}

N a_{2} C O_{3}

. If the amount of

N a_{2} C O_{3}

required to soften 100 L of hard water, which is 200 ppm

C a C O_{3}

x

g, then value of

x

N a_{2} C O_{3}

is widely used in softening of hard water. If 1 L of hard water required

0.0106 g

N a_{2} C O_{3}

, The hardness in ppm (parts per million i.e.,

10^{6}

C a C O_{3}

Q. Temporary hardness is due to

H C O_{3}^{-}

M g^{2 +}

C a^{2 +}

. It is removed by addition of

C a O

C a (H C O_{3})_{2} + C a O ⟶ 2 C a C O_{3} + H_{2} O

C a O

required to precipitate

2

C a C O_{3}

Q. Temporary hardness is due to

H C O_{3}^{-}

M g^{2 +}

C a^{2 +}

. It is removed by addition of

C a O

.

C a (H C O_{3})_{2} + C a O \to 2 C a C O_{3} + H_{2} O

C a O

(in g) required to produce

2

C a C O_{3}

precipitate is:

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