Question

The specific gravity of ethanol (CH3CH2OH) is 0.791, whereas the specific gravity of pure gasoline is 0.739. A blend of gasoline and ethanol needs to provide 2% of oxygen by weight to the resulting fuel. What volumetric fraction of the resulting blend needs to be ethanol?

Answer 1

What volumetric fraction of the resulting blend needs to be ethanol?

Oxygen /Ethanol=16 / (2 x 12 + 6x1 + 1x16)=0.347=34.7%

0.02=   X (mL eth) x 0.791 g eth /mL x 0.347 gO/g eth   / X (mL eth) x 0.791 g eth/mL + Y (mL gas) x 0.739 g gas/mL

0.02= 0.2745X   /   0.791X+0.739

=0.2745    /   0.791+ 0.739 Y /X

Y /X = 0.2745−0.02x0.79    / 0.02x0.739 = 17.50

Ethanol / Fuel blend = X(mL eth) / X(mL eth) + Y(mL gas)

=1 /    1+ Y/X

= 1/ 1+17.50

5.4% by volume