Calculate the molarity of a solution containing 5 g of NaOH (molar mass 40 g/mol) in 450 mL of solution.
A0.125 M
B0.556 M
C0.450 M
D0.278 M
Answer & Solution
Correct answer: D. 0.278 M
1. Molarity = moles of solute / volume of solution in litres.
2. Moles of NaOH = $5 / 40 = 0.125$ mol.
3. Volume = $450 / 1000 = 0.450$ L.
4. Molarity = $0.125 / 0.450 = 0.278$ M. (Option A is the mole count, not the molarity.)
_Source: NCERT Class 12 Chemistry Ch 1 "Solutions", p.3_
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