Consider the hypothetical elements X and Y. Suppose the enthalpy of formation for the compound XY is -336 kJ/mol, the bond energy for X2 is 414 kJ/mol, and the bond energy for Y2 is 159 kJ/mol. Estimate the XY bond energy in units of kJ/mol.
I worked this for you earlier but I wasn't sure if the delta Hf was -336 or not. It is; therefore, the delta Hrxn is -672 for the reaction as written.
X2 + Y2 ==> 2XY
(sum B.E.X2 + B.E.Y2)-(sum B.E. 2XY) = deltaHrxn*2
(414+159)-(2*XY) = -672
Solve for XY and I get 622.5 kJ/mol for X-Y.
Check that this way:
(1/2)X2 + (1/2)Y2 = XY
(sum B.E.X2 + B.E.Y2)-(B.E.XY) = ??
(207+79.5)-(622.5) = ??
(286.5)-(622.5) = -336
Check my thinking.
Consider hypothetical elements X and Y. Suppose the enthalpy of formation of the compound XY is −336 kJ/mol, the bond energy for X2 is 421 kJ/mol, and the bond energy for Y2 is 152 kJ/mol. Estimate the XY bond energy in units of kJ/mol.
To estimate the bond energy of XY, we can use the concept of enthalpy of formation and bond energy. The bond energy of XY can be approximated by the difference between the enthalpy of formation of XY and the sum of the bond energies of X2 and Y2.
Bond energy of XY ≈ Enthalpy of formation of XY - (Bond energy of X2 + Bond energy of Y2)
Bond energy of XY ≈ -336 kJ/mol - (414 kJ/mol + 159 kJ/mol)
Bond energy of XY ≈ -336 kJ/mol - 573 kJ/mol
Bond energy of XY ≈ -909 kJ/mol
Therefore, the estimated bond energy of XY is approximately -909 kJ/mol.
To estimate the bond energy for XY, we need to consider the enthalpy of formation and the bond energies of its constituent elements. The bond energy of XY can be estimated using the following equation:
Bond energy of XY = [(bond energy of X2) + (bond energy of Y2)] - (enthalpy of formation of XY)
Given:
- Enthalpy of formation of XY = -336 kJ/mol
- Bond energy of X2 = 414 kJ/mol
- Bond energy of Y2 = 159 kJ/mol
Substituting the values into the equation:
Bond energy of XY = (414 kJ/mol + 159 kJ/mol) - (-336 kJ/mol)
Simplifying:
Bond energy of XY = (573 kJ/mol) - (-336 kJ/mol)
Bond energy of XY = 573 kJ/mol + 336 kJ/mol
Bond energy of XY = 909 kJ/mol
Therefore, the estimated bond energy of XY is 909 kJ/mol.