Water chemistry document summarizes key points about water: - Water is a chemical compound H2O that consists of hydrogen and oxygen atoms and exists in liquid form between 32-212°F. It is crucial for all living things. - Sources of water include surface water, underground water, rainwater, and seawater. These sources contain various dissolved impurities like gases, inorganic salts, organic salts, suspended particles, and microbes. - The document describes types of hardness in water caused by calcium, magnesium, and other metal ions, and differentiates temporary and permanent hardness. It outlines methods to remove hardness including boiling, Clark's process, ion exchange, and using polyphosphates.

1. Water Chemistry
Prepared by
Muhammad Shakaib Qureshi
Msc (Analytical Chemistry)

2. Introduction
• Water is a chemical compound. Each molecule of water, H2O or
HOH, consists of two atoms of hydrogen bonded to one atom of
oxygen.
• Or
A transparent, odorless, tasteless liquid, a compound of hydrogen
and oxygen.
Freeze at 32F and Boil at 212F
• For the existence of all living beings (human, animals and plants),
water is very crucial. Almost all human activities—domestic,
agricultural and industrial, demand use of water although water is
nature’s most wonderful and abundant compound but only less than
1% of the world’s water resources are available for ready use. Hence
it is required to use it carefully and economically.

3. Sources of Water
• Surface water: It includes flowing water (streams and rivers)
and still water (lakes, ponds and reservoirs).
• Underground water: It includes water from wells and springs.
• Rain water
• Sea water
Dissolved Impurities
• (a) Dissolved gases: O2, CO2, H2S etc.
• (b) Inorganic salts:
• (i) Cations: Ca++, Mg++, Na+, K+, Fe++, Al+++ etc.
• (ii)Anions: CO3–, Cl–, SO4–, NO3– etc.

4. Impurities Continue
• Organic Salts
• Suspended Impurities
• (a) Inorganic: Clay and sand.
• (b) Organic: Oil globules, vegetables, and animal material.
• Colloidal Impurities
• Finally divided clay and silica Al(OH)3, Fe(OH)3, organic waste
products, colouring
• matter, amino acids etc.
• Microscopic Matters
• Bacteria, algae, fungi etc.

5. Sources of Impurities in water
• Gases (O2, CO2 etc.) are picked up from the atmosphere
by rainwater.
• Decomposition of plants and animals remains introduce
organic impurities in water.
• Water dissolves impurities when it comes in contact with
ground, soil or rocks.
• Impurities are also introduced in water when it comes in
contact with sewage or industrial waste.

6. Impurities in Various Sources
of Water
• River water contains dissolved minerals like chlorides,
sulphates, bicarbonates of sodium, magnesium, calcium and
iron. It also contains suspended impurities of sand, rocks and
organic matter. The composition of river water is not constant.
The amount of dissolved impurities in it depends on its
contacts of the soil. Greater the duration of contact, more
soluble is the minerals of soil in it.
• Lake water has high quantity of organic matter present in it
but lesser amount of dissolved minerals. Its chemical
composition is also constant.

7. Impurities in Various Sources
of Water
• Rain water is obtaining as a result of evaporation from the surface
water. Probably it is the purest form of natural water. But during its
downward journey through the atmosphere it dissolves organic and
inorganic suspended particles and considerable amount of industrial
gases like (CO2, NO2, SO2 etc.). Rain water is expensive to collect
and is irregular in supply.
• Underground water is free from organic impurities and is clearer in
appearance due to the filtering action of the soil. But it contains
large amount of dissolved salts.
• Sea water is very impure due to two reasons:
• 1. Continuous evaporation increases the dissolved impurities
content, which is
• further increased by the impurities thrown by rivers as they join sea.
• 2. It is too saline for most industrial uses except cooling.

8. Hardness of Water
• “Hardness in water is that characteristics, which prevents the
lathering of soap”.
• In other way we may define it as “soap consuming capacity of
water”.
Cause of Hardness
• Hardness is due to presence of certain salts of Ca2+, Mg2+
and other heavy metal ions like Al3+, Fe3+ and Mn2+ in water.

9. Reaction of soap with Soft
Water
• When soft water is treated with soap, lather is produced
according to the following reaction:
• C17H35COONa + H2O C17H35COOH + NaOH
• Soap (Sodium stearate) Stearic acid
• C17H35COONa + C17H35COOH Lather
• (Sodium stearate) Stearic acid

10. Reaction of Soap with Hard
water
• A sample of hard water, when treated with soap (sodium or
potassium salt of higher fatty acid like oleic, palmitic and
stearic acid), does not produce lather, but on the other hand
forms insoluble white scum or precipitate which do not
possess any detergent action. This is due to the formation of
insoluble soap of calcium and magnesium.

11. Types of Hardness

12. Effect of Hardness

13. Effect of Hardness

14. Types of water on basis of
hardness

16. Temporary hardness can be
removed by two methods
Boiling and
• Clark's process (the addition of a controlled quantity of slaked
lime).

17. Clark’s Process

18. PermanentHardness

19. Ion Exchange

20. By Polyphosphate

21. Thank You