Question

# Carbohydrates are metabolized according to: CH2O(aq)+O2(aq)=CO2(aq)+H2O(l) DeltaG= -509 KJ/mol How much energy is available per mole...

Carbohydrates are metabolized according to: CH2O(aq)+O2(aq)=CO2(aq)+H2O(l) DeltaG= -509 KJ/mol How much energy is available per mole of carbohydrate at typical blood levela of the chemicals? Assume 298 K [CH2O]= 5.0*10^-3 M [CO2]= 1.7*10^-3 M [O2]= 2.5*10^-4 M

The reaction:

CH2O(aq)+O2(aq) = CO2(aq)+H2O(l)

The data:

• ΔG0 = -509 KJ/mol
• [CH2O]= 5.0x10-3 M
• [CO2]= 1.7x10-3 M
• [O2]= 2.5x10-4 M

1) Calculate k using the equilibrium expression:

k = [products] / [reagents]

k = [CO2] / [CH2O] [O2]

k = 1.7x10-3 M / (5.0x10-3 M)(2.5x10-4 M)

k = 1360 M-1

2) Calculate ΔG (the available energy) using the formula:

ΔG = ΔG0 - RT*lnk

Where R = 8.314 J/molK and T = 298K

ΔG = -509 kJ/mol - (8.314 J/molK)(298K)*ln(1360)

ΔG = -509 kJ/mol - 17.9 kJ/mol

ΔG = -526.9 kJ/mol

So, the energy that is available is 526.9 kJ/mol carbohydrate.

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