Ethanol Questions HELP!!! (1 Viewer)

[nsbrando]

a. A sample of ethanol vapour in air has a concentration of 20% (v/v). Explain whether such a mixture will combust in the presence of an ignition source at room temperature?

b. Write a balance equation for the complete combustion of ethanol in the air

c. The molar enthalpy of combustion is -1367 kJ/mol. Calculate the heat energy released on the complete combustion of 100 litres of pure ethanol. (density of ethanol is 0.785 g/mL.)

 

[Rawf]

a. Yes it will combust because it's vapourised in air and thus we can light it and it will release heat (err not so sure about this one, but yeah i know it will combust)
b. C2H5OH(aq) + 3O2(g) --> 2CO2(g) + 3H2O(l)
c. 100L of ethanol = 0.785x1000x100 g = 78500g of ethanol
mol of ethanol = 78500/(12.01x2+1.008x6+16) = 1704mol
thus, heat released from combustion = 1367x1704 = 2329371.8kJ

 

[samantha.rose]

100L of ethanol = 0.785x1000x100 g = 78500g of ethanol

i don't get that part please explain. why is it x1000 x100?

 

[Rawf]

100L of ethanol = 0.785x1000x100 g = 78500g of ethanol

i don't get that part please explain. why is it x1000 x100?

There's 0.785g/mL of ethanol
1000mL = 1L
Thus, 0.785 x 1000 = 785g/L
We need to combust 100L of ethanol
Thus, 785x100g/100L
= 78500g/100L

So basically.. 0.785x1000x100g

 

[samantha.rose]

thank you