Question

A water sample has ppm level concentration of the following metals:\[{\text{Fe}} = {\text{0}}{\text{.2;Mn}} = 5.0;{\text{Cu}} = 3.0;{\text{Zn}} = 5.0.\] The metals that make the water sample unsuitable for drinking is:
A.\[{\text{Zn}}\]
B.\[{\text{Fe}}\]
C.\[{\text{Mn}}\]
D.\[{\text{Cu}}\]

Answer 1

Hint: There is a certain limit that is permissible for each of the metals, so that the water is safe for drinking. Ppm is also a unit of concentration called parts per million.

Complete step by step answer:
-Ppm or parts per million, as the name suggests it is parts of solute present in 1 million parts of solution. This is used for very dilute solutions in which concentration of solute is very less.
-This limit varies element to element, as some metals are more harmful than the others. Let’s look at the minimum level that is allowed for different elements:
-The minimum concentration of zinc that is safe for drinking water is 5 ppm above this it is harmful. In the given question it is given that the concentration of \[{\text{Zn}}\] is 5 ppm. So, \[{\text{Zn}}\] concentration is suitable for drinking purposes.
-The minimum allowed concentration of \[{\text{Fe}}\] is \[0.2\] ppm. In the question it is given to us that concentration of \[{\text{Fe}}\] is \[0.2\]. So, this concentration of iron is suitable for drinking purposes.
-Now coming to \[{\text{Cu}}\], the minimum safe concentration is 3 ppm and is the same as in the given question. Hence, this is also fit for water.
-But the safe concentration of \[{\text{Mn}}\] is \[0.05\] for drinking water but it is given in the question that it is 5 ppm hence, it is not suitable for drinking water.

So, the correct option is C.

Note:
These impurities affect various functions of water, such as the presence of iron and manganese interfere with dyeing and tanning. They even deposit in water lines and boilers. They can be removed with the help of aeration, coagulation, cation exchange and filtration etc.