Q111
General ScienceChemistry
How many grams of NaOH are needed to make 100ml. of a 0. 5 M solution of NaOH? (Atomic weight : Na = 23, 0 = 16, H = 1)
- a.2
- b.20
- c.4
- d.1
Answer: (A) 2
Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Molarity = moles/litre, so moles = $0.5 \times \frac{100}{1000} = 0.05$ mol. Mass = $0.05 \times 40 = 2$ grams.