PPM (Parts per million) - Definitions, Formula, Practice Problems and Frequently Asked Questions (FAQs)

On the evening of December 2, 1984, India witnessed one of its worst industrial incidents which led to the death of countless people in Bhopal. Thousands of people have died subsequently due to pollutants reaching their bodies through the air we breathe, the water we drink or the food we eat.

Each human being has a tolerance for such harmful chemicals but only to a certain limit. Beyond this, it can prove to be fatal. How can one ascertain those limits?

To overcome this problem, we need a concentration term which would help in throwing some light on such small but important values.

Parts per million (PPM) is the concentration term used for measuring such levels. Like each of the different concentration terms, PPM has a very specific use of providing information in minute quantities.

Table of contents

PPM (Parts per million)
Hardness of water
Degree of hardness
Example
International standard for drinking water
Practice problems
Frequently Asked questions-FAQs

PPM (Parts per million)

Generally, ppm concentration term is used when the amount of solute present in any solution is very small but significant due to its potential activity.
Parts per million is defined as the number of parts of the solute present in every 10⁶ parts of the solution.

E.g- 10 ppm solution means that 10 g of solute is present in every 10⁶g of solution.

ppm (parts per million) =

Hardness of water generally expressed in ppm.

Hardness of water

We know, that bicarbonates fsdfds of Ca & Mgcauses temporary hardness and chlorides (Cl^-) and sulphates kbhjb of Ca & Mgcause permanent hardness.

Degree of hardness

The number of parts of CaCO₃ or equivalent to various calcium and magnesium salts present in a million parts of water. ( ppm in terms of CaCO₃)

E.g- 160 ppm in terms of CaCl₂; means 160 g CaCl₂present in 10⁶g of solution.

Example:

Express hardness of the water in terms of CaCO₃, water contains 160 ppm CaCl₂

Answer: Equivalent weight of CaCl₂ = ⁼

Equivalent weight of CaCO₃ = ⁼ hvv

International standard for drinking water

Ions	Maximum permissible range
Flouride ion (F^-)	1 ppm
Sulphate )	< 500 ppm
Nitrate )	50 ppm

Metals	Maximum permissible range
Fe	0.2 ppm
Mn	0.05 ppm
Al	0.2 ppm
Cu	3.0 ppm
Zn	5.0 ppm
Cd	0.005 ppm

Practice problems:

Q1. A water sample contains 3 mg of dissolved oxygen per 1000 g of sample. Calculate concentration of oxygen in parts per million?

3 ppm
30 ppm
300 ppm
3000ppm

Answer:(A)

Solution: 1000 g of sample water contains 3 mg or 3 10 -3g oxygen.

Concentration of oxygen (ppm) = lnl

= = 3 ppm

Q2. A 400 g of body lotion sample has 0.1 g of fluoride. Find the concentration of fluoride ion in ppm

100 ppm
200 ppm
250 ppm
350 ppm

Answer:(C)

Solution: mass of solute (fluoride ion) = 0.1 g

Mass of solution = 400 g

Concentration of oxygen (ppm) =

= 250PP

Q3. A water sample contains 0.2 ppm carbon tetrachloride. How many molecules of carbon tetrachloride will be present in 0.5 g of the water sample.

khjgg

3.1
3.8
4.6
2.4

Answer: (D)

Solution: 80 ppm of CaSO₄ means 80 g of CaSO₄ present in 10⁶ g of solution.

80 g of Ca²⁺ ion present in 10⁶g of solution fgg

Question 2. Is ppm concentration term also used for chemicals in pollutants?
Answer: Air quality indexes used to set a standard for air constitutes clean air. Ppm or ppb is used to measure air pollutants.

Question 3. What is the permissible range of CO₂ in the atmosphere?
Answer: As explained by the Indian Meteorological Department (IMD) of India, the permissible values are

CO₂[ppm]	Air quality
2100	Bad Heavily contaminated indoor, air ventilation required
2000
1900
1800
1700
1600
1500	Mediocre Contaminated indoor, air ventilation recommended
1400
1300
1200
1100
1000	Fair
900	Fair
800	Good
700	Good
600	Excellent
500
400