Question

The equation shows one mole of ethanol fuel being burned in oxygen. Convert the energy released into its equivalent mass.
C2 H5 OH (l) + 3 O2 (g) --> 2 CO2 (g) + 3 H2O (l)
deltaH = -1418 kJ/mol

I am not sure where to begin with this one.

Answer 1

E=mc^2 ?

Answer 2

isnt that the only energy-mass relation?

Answer 3

but first, convert molar mass to kg and then perform the steps

Answer 4

Should I insert -1.418 * 10^6 for E?

Answer 5

no. use gram eq. wt. of ethanol to convert deltaH (in per mole) to per kG

Answer 6

could you show me perhaps?

Answer 7

1mole C2H5OH = 2(12)+5(1)+16+1 = 46
deltaH = -1418/46 10^6 J/kg
\[m = E/c^2\\
m=\frac{-1416\times10^6}{46}\times{1\over (3\times10^8)^2}
\]

Answer 8

but the question asks for energy released by 1 mole .
so,
\[m=\frac{-1416\times10^3}{(3\times10^8)^2}
\]

Answer 9

-ve sign can be ignored. indicates loss of mass