Question

1. This activity investigates the production of glucose on a small scale. The following analysis demonstrates what it would take to scale up the operation

a. The test stripes measure the concentration of glucose in solution in milligrams per deciliter (mg/dL). There are 100 mL per deciliter. Calculate how many milligrams of glucose are produced in 10 mL of solution if the test strip reads 1000 mg/dL. Hint: Be sure to use conversion factors and keep track of units.

b. Assume that the pretreatment process uses 0.5 g grass and 0.5 mL enzyme to generate 500 mg/dL of glucose in 10 mL of solution. How much grass and enzyme would you need to produce 5 g of glucose?

c. Calculate how much ethanol (in liters) would be produced from 5 g of glucose, assuming that you could distill 51.1 mg of ethanol made by yeast with 1 g of glucose. The density of ethanol is 0.789 g/L.

d. Fuels in the united states are generally expressed in gallon quantities. Calculate how many gallons of ethanol would be produced from 500 g of glucose. (1 L = 0.264 U.S. gallon)

Answer 1

a) 1000 mg ------------ 100 mL
   ? mg ------------ 10 mL
(1000*10) / 100 = 100 mg
100 mg of glucose are produced in 10 mL of solution.
b) To make 5 gm of glucose or 5000 mg of glucose we need to have 5 gm of enzyme and 5 mL of enzyme
   which is 10 times more than that of given.
c) C₆H₁₂O₆ ------------> 2C₂H₅OH + 2CO₂
   1 mole of glucose produces 2 moles of ethanol
mol of glucose = 5 gm / 180.1559 g/mol = 0.0277537 mol
   mol of ethanol produced = 2* 0.0277537 mol = 0.0555074 mol
   gms of ethanol produced = 0.0555074 mol * 46.06844 g/mol = 2.557139 gm
total ethanol produced = 2.557139 gm - 5*0.0511 gm = 2.301639 gm
   Ethanol produced in Litres =  2.301639 gm / 0.789 g/L = 2.9171 L
d) mol of glucose = 500 gm / 180.1559 gm/mol = 2.77537 mol
mol of ethanol produced = 2*2.77537 mol = 5.550747 mol
   gms of ethanol produced = 5.550747 mol * 46.06844 g/mol = 255.7143 gm
   Ethanol produced in L = 255.7143 gm / 0.789 g/L = 324.09924 L
1L -------------------- 0.264 gal
324.09924L ------------------- ? (324.09924*0.264) = 85.56219 gal
   85.56219 gallons of ethanol would be produced from 500 g of glucose.