The mass of NaOH (M = 40 g/mol) required to prepare 500 mL of a 0.20 M NaOH solution is
A{'text': '2.0 g', 'label': 'A'}
B{'text': '8.0 g', 'label': 'B'}
C{'text': '4.0 g', 'label': 'C'}
D{'text': '20 g', 'label': 'D'}
Answer & Solution
Correct answer: C. {'text': '4.0 g', 'label': 'C'}
1. Moles required = molarity × volume in L = 0.20 × 0.500 = 0.10 mol.
2. Mass = moles × molar mass = 0.10 × 40 = 4.0 g.
3. Dissolve 4.0 g of NaOH in water and make the final volume up to 500 mL.
4. This gives exactly a 0.20 M solution of NaOH.
_Source: NCERT Class 12 Chemistry, Unit 1 "Solutions", §1.2_
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