Unit-4: Water Chemistry

Question 1

What is the chemical formula of water?

Answer 1

H₂O, composed of two hydrogen atoms covalently bonded to one oxygen atom.

Question 2

What gives water its high boiling and melting points?

Answer 2

Extensive hydrogen bonding.

Question 3

Why is water called a ‘universal solvent’?

Answer 3

Due to its polarity and ability to dissolve many ionic and polar substances.

Question 4

Why is water colorless with a faint blue tint?

Answer 4

Weak absorption of light at around 750 nm wavelength.

Question 5

Name two key physical properties of water.

Answer 5

High surface tension and low thermal conductivity.

Question 6

What is the charge distribution in a water molecule?

Answer 6

Oxygen is partially negative, and hydrogen is partially positive.

Question 7

What causes water molecules to aggregate?

Answer 7

Hydrogen bonding.

Question 8

What is potable water?

Answer 8

Water that is safe for human consumption.

Question 9

Define brackish water.

Answer 9

Water with salinity between freshwater and seawater.

Question 10

What is grey water?

Answer 10

Domestic wastewater with lower nitrogen and phosphorus levels than black water.

Question 11

What is black water?

Answer 11

Water contaminated with feces or urine.

Question 12

What is water pollution?

Answer 12

Contamination of water bodies, affecting their physical, chemical, or biological properties.

Question 13

What are the two chief sources of water pollution?

Answer 13

Point source and non-point source pollution.

Question 14

Define eutrophication.

Answer 14

Excessive nutrients in water leading to algae blooms and oxygen depletion.

Question 15

What is a common cause of chemical water pollution?

Answer 15

Industrial discharge of metals, solvents, and pesticides.

Question 16

What is surface water pollution?

Answer 16

Pollution of rivers, lakes, and oceans by hazardous substances.

Question 17

How does groundwater pollution occur?

Answer 17

Pesticides and chemicals leach into aquifers through rainwater.

Question 18

What is oil spillage pollution?

Answer 18

Oil spills in water that harm marine life and birds.

Question 19

What does BOD5 measure?

Answer 19

The amount of oxygen needed by microorganisms to break down organic material in 5 days.

Question 20

What is the acceptable pH range for treated wastewater?

Answer 20

Between 5 and 9.

Question 21

Name three key parameters for water quality.

Answer 21

COD, TSS, and Total Nitrogen.

Question 22

Name one method to control industrial wastewater pollution.

Answer 22

Recycling and reuse of water.

Question 23

How can farmers reduce agricultural runoff pollution?

Answer 23

By minimizing chemical usage and manuring farm waste.

Question 24

What is biomagnification?

Answer 24

Accumulation of non-biodegradable chemicals in the food chain.

Question 25

What is the maximum permissible COD level for treated water?

Answer 25

120 mg/L.

Question 26

What is the acceptable limit of total coliforms in treated water?

Answer 26

Less than 400 MPN per 100 mL.

Question 27

What should be the maximum permissible level of suspended solids?

Answer 27

35 mg/L.

Question 28

What is Total Suspended Solids (TSS)?

Answer 28

Particles suspended in water that do not dissolve.

Question 29

How does oil spillage affect seabirds?

Answer 29

Oil sticks to their feathers, reducing their ability to fly.

Question 30

What is the role of biological nitrogen removal in wastewater treatment?

Answer 30

Converts ammonia to nitrogen gas, reducing toxicity.