gchem help

[mgdent]

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its getting late and my brain is shutting down so i cant figure this out lol. the question was what is the mole fraction of C2H5OH in aq soln that is 3.86 m C2H5OH and 2.14 m CH3OH.

X ethanol= mol ethanol/ mol total
X ethanol= 3.86 / (3.86+2.14+55.55)

I get everything except the 55.55 from water. Why would you do 1000 g /18 g/mol to get the moles of water.. Where did 1000 grams come from. Thanks!

 

[rpatel8]

Because it is molal, it is mols/liters of solution so it would be 1L of water in aq solution which is the same as 1000 g water

 

[toothfairy05]

its getting late and my brain is shutting down so i cant figure this out lol. the question was what is the mole fraction of C2H5OH in aq soln that is 3.86 m C2H5OH and 2.14 m CH3OH.

X ethanol= mol ethanol/ mol total
X ethanol= 3.86 / (3.86+2.14+55.55)

I get everything except the 55.55 from water. Why would you do 1000 g /18 g/mol to get the moles of water.. Where did 1000 grams come from. Thanks!

careful using m for M (m is moles per kg, while M is moles/Liter)....it can confuse you 🙂