G-chem, solution?

[Dencology]

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guys can you help me with this question?


Given that the molecular wight of ethyl alcohol is 46 and that of water is 18. how many grams of ethyl alcohol must be mixed with 100mL of water for the mole fraction of ethyl alcohol to be 0.2?

thanks.

 

[HowAboutDAT]

guys can you help me with this question?


Given that the molecular wight of ethyl alcohol is 46 and that of water is 18. how many grams of ethyl alcohol must be mixed with 100mL of water for the mole fraction of ethyl alcohol to be 0.2?

thanks.

well since 100 ml of water is equal to 100 grams of water, the number of moles of water is 5.5. The formula for mole fraction is moles of ethyl alcohol (let this equal x) over total moles (let this equal x +5.5), so set up an equation.
.2 = x/(x+5.5)

Cross multiply and solve for x. Hope this helps!

 

[Dencology]

well since 100 ml of water is equal to 100 grams of water, the number of moles of water is 5.5. The formula for mole fraction is moles of ethyl alcohol (let this equal x) over total moles (let this equal x +5.5), so set up an equation.
.2 = x/(x+5.5)

Cross multiply and solve for x. Hope this helps!

great. thanks.

 

[rick4234]

great. thanks.

Yes, you are right 😉 , or :

0.2=(x/46) / { 100/18 +x/46 } where x is gram.