Question

Mass of ethanol to be added to 1.0 kg water to have the mole fraction of ethanol equal to 0.20 ?
a) 63.89g
b) 6.39 g
c) 638.89 g
d) 683.89 g
I want with solution and
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Answer 1

Answer:

Solution:

·  № of moles of water present in 1000- g of water = 1000/18= 55.55

· When the mole fraction of water is 0.80 and the mole fraction of ETHANOL is 0.20, number of moles of ETHANOL to be added to the mixture= 55.55/4  = 13.8875- moles .

· So weight of ethanol to be added to 1- Kg of water= 13.8875 x 46 = 638.9- g.

So if we mix 1- Kg of water to 638.89- g of ETHANOL the mole- fraction of ETHANOL will be 0.20.

so the answer is c)638.89 g

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Explanation: