Question

The standard enthalpies of formation of CO2(g) ,H2O(l) and glucose (s) at 25°C are-400kJ,-300 kJ/mol and-1300kJ/mol,respectively. The standard enthalpy of combustion per gram of glucose at 25°C is
(1)2900kJ
(2)-2900kJ
(3)-16.11 kJ
(4)16.11kJ

Answer 1

Question #75774, Chemistry / Physical Chemistry / Completed

The standard enthalpies of formation of CO2(g), H2O(l) and glucose (s) at 25°C are -400kJ, -300 kJ/mol and -1300kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at 25°C is

(1) 2900kJ

(2) -2900kJ

(3) -16.11 kJ

(4) 16.11 kJ

Solution:

C6H12O6 + 6O2 = 6CO2 + 6H2O

6(-400) + 6(-300) - (-1300) = -2400 - 1800 + 1300 = -2900 kJ/mol

M = 180 g/mol

-2900/180 = -16.11 kJ/g

Answer: (3) -16.11 kJ/g.

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