Question

Fiji is a small country in the South Pacific, whose main export crop is sugar. Fiji produces 300,000 t/y of sugar, and imports 300,000 t of fossil petroleum fuel. If all this sugar were converted to ethanol, what proportion of petroleum imports could it replace?

Answer 1

From the theory, we have ==>

1 mole of sugar (table sugar) produces 4 pole of ethanol

Molar mass of sugar =  342.2965 g

Molar mass of ethanol = 46.07 g

Therefore, 342.2965 g of sugar produces 4*46.07 g of ethanol

==> 1 kg of sugar produces (4*46.07/342.2965) = 0.5384 kg  of ethanol

==> 1 t of sugar produces 0.5384 t of ethanol

==> 300000 t of sugar produces 0.5384*300000 = 161520 t of ethanol

Since, calorific value of 1 kg ethanol is approximately equal to 0.64 times that of 1 kg fossil petroleum fuel (petrol)

Therefore, energy from 161520 t of ethanol = energy from 0.64*161520 t =103372.8 t 103373 t of fossil petroleum fuel

Since, total import of fossil petroleum fuel was 300,000 t

Therefore, % of import of fossil petroleum fuel reduced = 103373 t / 300,000 t = 0.3446 = 34.46 % ==> ANSWER