MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
If water is added to vessel A to make 600 mL of solution, which of the following will be the molarity of the solution?
Think it through first, then pick an option.
- a 0.6 M
- b 0.8 M
- c 1.0 M
- d 1.2 M
Answer and explanation
Correct answer: c 1.0 M
Limestone is CaCO₃, M = 40 + 12 + 48 = 100. 60 g = 0.6 mol; 600 mL = 0.6 L; S = 0.6 ÷ 0.6 = 1.0 M. By the formula: 60 = (S × 600 × 100)/1000, S = 1.
Why the other options are wrong
- a 0.6 M: 0.6 is the number of moles (60 g ÷ 100 = 0.6 mol), not the molarity; molarity = 0.6 mol ÷ 0.6 L = 1.0 M.
- b 0.8 M: 0.8 M would need 0.48 mol (48 g of CaCO₃); here 60 g = 0.6 mol, so S = 0.6 ÷ 0.6 = 1.0 M.
- d 1.2 M: 1.2 M comes from dividing 0.6 mol by 500 mL (0.5 L); the solution is 600 mL, so the answer is 1.0 M.
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