Question 2

a. Dolomite and lime stone mining in the basins of the Indravati river is widely known in the Orissan district of Koraput. A number of families are residing along the river. They use the water from that river to wash their dishes and clothes. Their utensils' inner surface develops thick, sticky coatings of certain deposits over a period of time. The mineral salts that are left behind after washing cause soiled and dirty-looking garments. They frequently need to spend more money on buying soaps.
(i) If you had to name the thick coating of deposits on the inner surface of utensils, what would it be called and what would be its expected chemical composition? (1.5 marks)
(ii) Give a strong justification for why they routinely spend more money on soap purchases. (1.5 marks)
(iii) What mineral salts can be left behind on their clothing? (1 mark)

b. The Yamuna River, India's capital New Delhi's artery, was analysed for water, yielding the following findings: H₂SO₄ is present at a concentration of 392 mg/L along with MgSO₄ = 48 mg/L, CaSO₄ = 544 mg/L, NaCl = 250 mg/L and SiO₂ = 8.4 mg/L. Nearly 32 million people in New Delhi receive water from the Yamuna. Only one lakh people will receive the daily recommended water consumption of 100 litres per person. Before serving the population for only one lakh, determine how much soda and lime is needed for water treatment. (3 marks)

c. Calculate permanent and temporary hardness of water if 60 mL of hard standard water containing 1.5 g CaCO₃ per litre required 40 mL of EDTA solution for end point and 50 mL of water sample required 30 mL of EDTA solution, while the same amount of water after boiling required 20 mL EDTA solution. (3 marks)