Calculate the mole fraction of HCL in an aqueous solution that contains 33.6% HCL by mass

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sciencesolve | Teacher | (Level 3) Educator Emeritus

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You need to convert the percents in grams, hence,  `33.6% HCl ` means 33.6 grams of HCl.

You need to convert the mass of 33.6 grams of HCl into moles, such that:

moles `HCl = 33.6/(M_(HCl))` => moles of `HCl = 33.6/36.46`

`M_(HCl)` represents the molar mass of HCl `= 36.46`

moles of `HCl = 0.921`

The rest of 66.4 grams of solution represents water,  hence, you need to convert the mass of `H_2O` into moles, such that:

moles of water `= 66.4/(M_(H_2O))`

moles of water `= 66.4/18 = 3.68`

Evaluating the total number of moles yields:

moles HCl + moles of water = `0.921 + 3.68 = 4.609`

You may evaluate the mole fraction of HCl, such that:

mole fraction of `HCl = 0.921/4.609` => mole fraction of `HCl = 0.199`

Hence, evaluating the mole fraction of HCl, under the given conditions, yields mole fraction of `HCl = 0.199.`

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