Question

the number of molecule in one litre of water is (density of water =1g/mL)
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Answer 1

55.56

Answer: The density of water is 1g/cc, so if you do dimensional analysis, you can find that in 1 L of water, there is 55.56 mol. 1ml * 1g/ml = 1g of water in 1 ml. 1g * 1mol/18g = 1/18 moles = about 0.0556 moles in 1ml (=1g) of water.