The mole fraction of hcl in a solution prepared by dissolving 5.5 g of hcl in 200 g of c2h6o is the density of the solution is 0.79 g/ml.

The
all that we search for is the number of mole of HCl and the number of mole of C2H6O

M(HCl) = 5.5g/ mole of HCl , so mole of HCl = 5.5/M(HCl), where M(HCl) is the molar mass.
M(HCl) = 1+ 36.5= 37.5 

moles of HCl = 5.5/37.5=0.14 

M(C2H6O) = 200g / moles of C2H6O, so moles of C2H6O=200g / M(C2H6O)

M(C2H6O)= 2x12+ 6 + 16=46,

moles of C2H6O=200g / 46 =4.35  moles 

the sum of the moles is    0.14 + 4.35  = 4.501 moles

finally,  The mole fraction of hcl in a solution prepared by dissolving 5.5 g of hcl in 200 g of c2h6o is 0.031

because it can be found by  0.14 / 4.501= 0.031

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