# an athlete is given 180g of glucose (c6 h12 o6). he utilises 50% of the energy due to internal combustionin the body. In order to avoid storage of energy oin the body, calculate the mass of water he'll need to perspire. Given enthalpy of combustion of glucose is -2800 kj/mol and enthalipy os evaporation of water is 44kj/mol.

Energy available for after the internal combustion process = 50% of 2880 kJ/mol = (50 x -2880)/100 = -1440 kJ/mole
Energy from 180g of glucose left =  1440 kJ/mole because 50% is wasted
The amount of energy used for muscular work by athletic  will be the same the amount of energy liberated from water.(internal energy)
Enthalpy of evaporation on water = 44kJ/mole.
Since
∆H = ∆U + nRT
∆U = -1440 kJ/mole
∆H = 44kJ/mol.
T = 373 K for water to evaporate.
R = 0.008314 kJ/mol.

44  = -1440 + (w/m)(0.008 kJ/K/mol)(373 K)
w = mass of water
m = molar mass of water = 18g
m = [(44+1440)(18)]/[(0.008.314)(373 K)]
m =  11840/2.984 = 4082 g
which is almost equal  to 4.082 Liters

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