Glycine,C2H502N, is important for biological energy.Find the heat of combustion deltaHrxn.
Delta H [C2H5O2N]=-537.3 kj/mol
DeltaH [ CO2(g)=-393.5 kj/mol
DeltaH[H2O(l)]-285.8 kj/mol
Write and balance the combustion reaction. Then
DHrxn = (n*DHfproducts)-(n*DHfreactants)
To find the heat of combustion (ΔHrxn) for glycine (C2H5O2N), we need to consider the stoichiometry of the combustion reaction. The general equation for the combustion of a hydrocarbon can be written as follows:
C2H5O2N + aO2 → bCO2 + cH2O + dN2
In this equation, 'a' represents the number of oxygen molecules required, 'b' represents the number of carbon dioxide molecules produced, 'c' represents the number of water molecules produced, and 'd' represents the number of nitrogen gas molecules produced.
To determine the values of 'a', 'b', 'c', and 'd', we need to balance the equation by ensuring that the number of atoms of each element is the same on both sides. For glycine, we have:
C: 2 atoms on the left (C2H5O2N) and '2b' atoms on the right (bCO2)
H: 5 atoms on the left (2xH5O2N) and '2c' atoms on the right (cH2O)
O: 3 atoms on the left (2xH5O2N) and '2a' atoms on the right (2aO2)
N: 1 atom on the left (C2H5O2N) and 'd' atoms on the right (dN2)
By balancing the equation, we find that 'a' would be 3, 'b' would be 2, 'c' would be 3, and 'd' would be 1.
Now, we can calculate ΔHrxn for glycine's combustion using the given enthalpy changes:
ΔHrxn = (2bΔH[CO2]) + (2cΔH[H2O]) - (ΔH[C2H5O2N] + 2aΔH[O2])
Plugging in the given values:
ΔHrxn = (2*2*-393.5) + (2*3*-285.8) - (-537.3 + 2*3*0)
Simplifying:
ΔHrxn = -1574 + -1714.4 + 537.3
ΔHrxn = -2750.1 kJ/mol
Therefore, the heat of combustion (ΔHrxn) for glycine is approximately -2750.1 kJ/mol.