Use bond enthalpies and mean bond enthalpies to estimate a t

Use bond enthalpies and mean bond enthalpies to estimate (a) the enthalpy of the anaerobic breakdown of glucose to lactic acid in cells that are starved of O2, C6H12O6(aq) --> 2 CH3CH(OH)COOH(aq), and (b) the enthalpy of combustion of glucose. Ignore the contributions of enthalpies of fusion and vaporization.

Solution

Given reaction

C₆H₁₂O₆ (s) >>> 2 CH₃CHOHCOOH (s)

Change in enthalpies:

H_rection= 2H_(lactic) -H_(glucose).

We know that:H for glucose and lactic acid are -1274 and -694 kJ/mol, at 298 K.

therefore:

H_rection = 2x(-694) –(-1274)

H_rection= -114 kJ/mol.