C2H5O2N is an important compound. The combustion reaction of glycine proceeds according to this equation:
4C2H5O2N + 9O2 ---> 8Co2 +10H2O +2N2
which is = -3857 kJ
Given CO2 is -393.5 kJ/mol
Given H2O is -285.6
Calculate the standard molar enthalpy of formmation of glycine.
What I have looks like this:
4X +9(0) - 8(-393.5) +10(-285.8) +2(0)
Products - Reactants
with 0 being the natural elements
4X - -6003 does not get me the answer so what am I doing wrong?
I think it's too easy to get a sign wrong trying to do all of it at one time.
DHrxn = [n*DHproducts]-[n*DHreactants]
-3357 = (8*DHfCO2)+(10*DHH2O)] - (4*DHgly)
-3357 = (8*-393.5) + (10*-285.8)] - 4X
-3357 = (-3148)+(-2858)] - 4X
-3357 = -6006 - 4X; now I switch and
4X = -6006 + 3357 and solve for X.
Something like 662 kJ/mol but that isn't exact. I ALWAYS check these things by
DHrxn = (n*DHproducts)-(n*DH reactants) and see if I come out with 3357 kJ for the reaction.
To calculate the standard molar enthalpy of formation of glycine (C2H5O2N), we need to use the equation of the combustion reaction and the given enthalpies of formation for CO2 and H2O.
The standard molar enthalpy of formation of a compound is the change in enthalpy that occurs when one mole of the compound is formed from its elements in their standard states. In this case, we want to find the enthalpy change for the formation of glycine.
By comparing the given combustion equation to the desired formation equation, we can see that 4 moles of glycine are formed when 8 moles of CO2 and 10 moles of H2O are produced. Therefore, the stoichiometric coefficient for glycine in the formation equation is 4.
Now, let's calculate the enthalpy change for the formation of one mole of glycine using the enthalpies of formation for CO2 and H2O:
ΔH = (8 moles of CO2 × -393.5 kJ/mol) + (10 moles of H2O × -285.6 kJ/mol)
ΔH = -3148 kJ
Since 4 moles of glycine are formed in the combustion reaction, we can divide the enthalpy change by 4 to get the enthalpy change for the formation of 1 mole of glycine:
ΔH of formation of glycine = -3148 kJ / 4
ΔH of formation of glycine = -787 kJ/mol
Therefore, the standard molar enthalpy of formation of glycine is -787 kJ/mol.
To calculate the standard molar enthalpy of formation of glycine (C2H5O2N), we need to use the Hess's Law and the enthalpies of formation for the products involved in the combustion reaction. The enthalpy change of a reaction depends only on the initial and final states and is independent of the pathway taken.
Here's how we can calculate it:
1. First, we need to identify the compounds in the overall reaction equation and find their enthalpies of formation.
C2H5O2N (glycine) is not given, so we need to find its enthalpy of formation.
CO2 (carbon dioxide) has an enthalpy of formation of -393.5 kJ/mol.
H2O (water) has an enthalpy of formation of -285.6 kJ/mol.
N2 (nitrogen gas) has an enthalpy of formation of 0 kJ/mol.
2. Next, we need to calculate the total enthalpy change of the reaction based on the given balanced equation:
4C2H5O2N + 9O2 -> 8CO2 + 10H2O + 2N2
The total enthalpy change is -3857 kJ.
3. Now we can use Hess's Law to calculate the enthalpy change of formation for glycine (C2H5O2N).
The enthalpy of formation is obtained by subtracting the enthalpies of formation of the products from the enthalpies of formation of the reactants, multiplied by their respective stoichiometric coefficients.
Enthalpy of formation of glycine = [8 * Enthalpy of formation of CO2 + 10 * Enthalpy of formation of H2O + 2 * Enthalpy of formation of N2] - [4 * Enthalpy of formation of C2H5O2N + 9 * Enthalpy of formation of O2]
4. Substitute the given enthalpies of formation:
Enthalpy of formation of glycine = [8 * (-393.5 kJ/mol) + 10 * (-285.6 kJ/mol) + 2 * 0 kJ/mol] - [4 * Enthalpy of formation of C2H5O2N + 9 * 0 kJ/mol]
5. Solve the equation:
Enthalpy of formation of glycine = (-3148 kJ/mol) - [4 * Enthalpy of formation of C2H5O2N]
6. Rearrange the equation to solve for the enthalpy of formation of glycine:
[4 * Enthalpy of formation of C2H5O2N] = (-3148 kJ/mol) - Enthalpy of formation of glycine
7. Substitute the given total enthalpy change (-3857 kJ/mol) as the standard enthalpy change for the reaction:
(-3857 kJ/mol) = (-3148 kJ/mol) - Enthalpy of formation of glycine
8. Solve for the enthalpy of formation of glycine:
Enthalpy of formation of glycine = -3857 kJ/mol - (-3148 kJ/mol)
Enthalpy of formation of glycine = -3857 kJ/mol + 3148 kJ/mol
Enthalpy of formation of glycine = -709 kJ/mol
Therefore, the standard molar enthalpy of formation of glycine (C2H5O2N) is -709 kJ/mol.