Exams › JEE Advanced › Chemistry
A water sample has hardness due to the presence of CaCl2 only. A 10 kg sample of this hard water requires 10.6 g of Na2CO3 for complete removal of hardness. What is the degree of hardness of the water sample expressed in ppm of CaCO3? [Atomic masses: Na = 23, Ca = 40, Cl = 35.5]
- 500 ppm
- 1000 ppm
- 1500 ppm
- 2000 ppm
Correct answer: 1000 ppm
Solution
10.6 g of Na2CO3 = 0.1 mol, producing 0.1 mol CaCO3 = 10 g = 10,000 mg. 10 kg water = 10 L, so hardness = 10,000 mg / 10 L = 1000 ppm.
Related JEE Advanced Chemistry questions
- Which of the following methods can effectively reduce the concentration of photochemical smog in the atmosphere?
- Among the following statements, how many are correct? (A) Classical smog is a mixture of smoke, fog, and SO2. (B) Photochemical smog leads to cracking of rubber. (C) Clean water has a BOD (Biochemical Oxygen Demand) value less than 5 ppm, while highly polluted water has a BOD greater than 17 ppm. (D) Aqueous NaOH solution is used in the Bayer's process for concentrating red bauxite. (E) BeO is purely acidic in nature. (F) Barium salts give an apple-green colour in the flame test. (G) The H-H bond dissociation energy is greater than the C-C bond energy.
- Which of the following permissible limits for pollutants in drinking water are correctly stated? (i) Sulphate — less than 500 ppm (ii) Fluoride — 1 ppm (iii) Nitrate — 50 ppm (iv) Lead — 50 ppm
- A 100 mL water sample contains 0.81 g of calcium bicarbonate (molar mass 162 g/mol) and 0.73 g of magnesium bicarbonate (molar mass 146 g/mol). Express the total hardness of this water in terms of equivalent CaCO3 content in ppm (mg per litre).
- Let X% of sunlight reach the Earth's surface while Y% is trapped by greenhouse gases. Find the value of (X - Y).
- Match List-I with List-II: List-I: (P) Carbon dioxide, (Q) Water vapour, (R) Ozone, (S) Sulphur dioxide. List-II: (1) Greenhouse gas, (2) Linear, (3) Unstable, (4) Responsible for acid rain, (5) Oxidizing agent. Choose the correct matching.
⚔️ Practice JEE Advanced Chemistry free + battle 1v1 →