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Stoichiometric Calculations

Temporary har...

Question

Temporary hardness is due to $H C O_{3}^{-}$ of $M g^{2 +}$ and $C a^{2 +}$ . It is removed by addition of $C a O$ .
$C a (H C O_{3})_{2} + C a O \to 2 C a C O_{3} + H_{2} O$
Mass of $C a O$ (in g) required to produce $2$ g of $C a C O_{3}$ precipitate is:

A

2.00

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B

0.56

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C

0.28

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D

1.12

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Solution

The correct option is A $0.56$
Molecular weight of $C a C O_{3}$ and $C a O$ are $100$ g/mol and $56$ g/mol respectively.
$2$ equivalents of $C a C O_{3}$ requires $1$ equivalents of $C a O$ .
Amount of $C a O$ required to produce $2$ g of $C a C O_{3}$ $= \frac{2 \times 56}{2 \times 100} = 0.56$

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Similar questions

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 bicarbonates of

M g^{2 +}

C a^{2 +}

. It is removed by addition of CaO as follows:

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

Mass of CaO required to precipitate

2 g C a C O_{3}

Q. Temporary hardness is due to bicarbonates of

M g^{2 +}

C a^{2 +}

. It is removed by addition of CaO as follows:

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

Mass of CaO required to precipitate

2 g C a C O_{3}

Following reaction is used to remove temporary hardness which is due to dissolved bicarbonates of

C a^{2 +}

M g^{2 +}

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

Actually lime (

C a O

) is added which in

H_{2} O

C a (O H)_{2}

and precipitates

C a C O_{3}

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

10

L of hard water requires

0.56

C a O

, temporary hardness of

C a C O_{3}

x \times 10^{2}

x

Q. Hardness of water is measured in terms of ppm (parts per million) of

C a C O_{3}

. It is the amount (in g) of

C a C O_{3}

10^{6} g H_{2} O

. In a sample of water,

10

0.56

C a O

to the remove temporary hardness of

H C O_{3}^{-}

.

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

Temporary hardness is :

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