Question

The hardness of water sample containing 2 x 10-³ g of CaCO3 dissolved in 1 L of water is expressed as

20 ppm

2 ppm

200 ppm

0.2 ppm​

Answer 1

Option B: 2 ppm

I am late so the other one answered it

Answer 2

The hardness of water is expressed as  $2 \mathrm{ppm}$.

Hardness of water

Water hardness is defined as the total calcium and magnesium ion concentration in a water sample, represented as calcium carbonate concentration. Water hardness can be divided into two categories:

Temporary hardness

Only magnesium and calcium bicarbonates are found in temporary hard water. Boiling will get rid of it.

Permanent hardness

Calcium and magnesium sulphates, as well as chlorides, are found in hard water. This can not be removed by boiling.

Given:

Weight of CaCO3 dissolved in $1 \mathrm{~L}=2 \times 10^{-3} \mathrm{~g}$.

Explanation:

As, $1 \mathrm{~L}=10^{3} \mathrm{ml}$ contains $2 \times 10^{-3} \mathrm{~g} \mathrm{CaCO_{3} }$.

ppm (parts per million) is the unit which is same as $\mathrm{g}$ of $\mathrm{CaCO_{3} }$ in $10^{6} \mathrm{ml}$.

If,

$10^{3} \mathrm{ml}$ contains    $2 \times 10^{-3} \mathrm{~g} \mathrm{CaCO_{3} }$

Then,

$10^{6} \mathrm{ml}$ contains $2 \times 10^{-3} \times 10^{3} \mathrm{~g} \mathrm{CaCO} 3=\mathrm{2 p p m}$.

Thus, the hardness present in 1 L of water is  $2 \mathrm{ppm}$.

To know about causes of hardness, here

https://brainly.in/question/2688820?msp_poc_exp=2

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