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The enthalpy of combustion of glucose is -2808 kJ/mol at 25degree C .How many grams of glucose do you need to consume(assume wt=62.5kg). (a) to climb a flight of stairs rising through 3M. (b) to climb a mountain of altitude 3000M?  Assume that 25% of enthalpy can be converted to useful work.

Asked by m.nilu 23rd September 2018, 11:23 PM
Answered by Expert
Answer:
 
As given, 1 mole of glucose on combustion releases = -2808 kJ/mole at 25°C.
 
As we have asked, only 25% of enthalpy can be converted into work,
 
hence, For 1 mole of glucose = negative 2808 space cross times space 25 over 100 equals space minus 702 space kJ
The molecular mass of sugar is 342 g hence it will provide -702 kJ energy to performed work.
 
As we know that work done is equal to the change potential energy
 
Work done = P. E. = mgh
 
Where m = mass, g = gravitational acceleration and h = height 
 
weight = mg = 62.5 Kg
 
Now, let us calculate the energy consumed,
 
Case 1.: for h = 3 m
 
Work done = mgh = 62.5 X 3 = 187500 J = 187.5 kJ
 
Since on combustion of 342 gm of glucose 702 kJ energy released
 
 Therefore, 187.5 kJ of energy released by = 342 over 702 cross times 0.187 space equals space 0.091 space straight g space of space glucose
 
Case 2: For h= 3000 m
 
Work done = mgh = 62.5 X 3000 = 187.5 J = 0.187 kJ
 
Since on combustion of 342 gm of glucose 702 kJ energy released
 
 Therefore, 0.187 kJ of energy released by =   342 over 702 cross times 187.5 space equals 91.35 space straight g space of space glucose
 
 
Answered by Expert 19th November 2018, 4:34 PM
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