The energy change �H associated with the
reaction NBr3(g) + 3H2O(g) ! 3HOBr(g) + NH3(g)is +81 kJ/mol rxn.
These bond energy values might be useful:O-H 459 kJ/mol; N-H 386 kJ/mol;O-Br 201kJ/mol. The strength of the N Br bond is
△H=bonds broken-bonds formed
Broken Bonds:
O-H=6(459kJ/mol)
N-Br=3(X kJ/mol)
------------
Bonds Broken=2754kJ/mol + 3(X kJ/mol)
Bonds Formed:
O-H=3(459kJ/mol)
O-Br=3(201kJ/mol)
N-H=3(386 kJ/mol)
-------------
Bonds Formed= 3138kJ/mol
+81kJ/mol=[2754kJ/mol + 3(X kJ/mol)]- 3138kJ/mol
* resolve for X
N-Br=155kJ/mol
Well, the strength of the N Br bond is quite... exhilarating! It's like a rollercoaster ride, but for molecules. Picture this: the N and the Br holding hands, tightly intertwined, not wanting to let go. They have a special connection that can only be broken with the right amount of energy. And that energy is quite high, my friend. The N Br bond is strong, sturdy, and not easily broken. Just like a really stubborn knot that refuses to come undone. So, if you ever find yourself in need of untying an N Br bond, you better bring some serious energy along for the ride!
To determine the strength of the N-Br bond, we can use the concept of bond energy.
The reaction given is:
NBr3(g) + 3H2O(g) → 3HOBr(g) + NH3(g) (ΔH = +81 kJ/mol)
In this reaction, three N-Br bonds are broken, and three new O-Br bonds and one N-H bond are formed.
The energy change associated with breaking bonds is positive because energy is required. The energy change associated with forming bonds is negative because energy is released.
Let's calculate the energy change for breaking the N-Br bonds:
Energy change for breaking 3 N-Br bonds = 3 × bond energy of N-Br
Energy change for breaking 3 N-Br bonds = 3 × 201 kJ/mol = 603 kJ/mol
Now let's calculate the energy change for forming the bonds:
Energy change for forming 3 O-Br bonds = 3 × bond energy of O-Br
Energy change for forming 3 O-Br bonds = 3 × 201 kJ/mol = 603 kJ/mol
Energy change for forming 1 N-H bond = bond energy of N-H
Energy change for forming 1 N-H bond = 386 kJ/mol
Now, let's calculate the total energy change:
Total energy change = Energy change for breaking bonds - Energy change for forming bonds
Total energy change = (603 kJ/mol) - (603 kJ/mol + 386 kJ/mol)
Total energy change = 603 kJ/mol - 989 kJ/mol
Total energy change = -386 kJ/mol
The negative value indicates that energy is released during the formation of bonds, which is typical for exothermic reactions.
Therefore, the strength of the N-Br bond is 386 kJ/mol.
To calculate the energy change associated with a reaction, we can use the concept of bond energies. In this case, we need to determine the strength of the N-Br bond.
The given reaction involves breaking one N-Br bond in NBr3 and forming three new HO-Br bonds in HOBr. We also need to account for the bond energy of the existing N-H and O-H bonds.
The energy change (∆H) for the reaction can be calculated using the equation:
∆H = (sum of bond energies of the bonds broken) - (sum of bond energies of the bonds formed)
Analyzing the reaction:
Reactants:
1 N-Br bond (broken)
3 H-O bonds (broken)
Products:
3 H-O bonds (formed)
1 N-H bond (formed)
3 O-Br bonds (formed)
To calculate the energy change, we'll use the given bond energy values:
N-Br bond energy = 201 kJ/mol
O-H bond energy = 459 kJ/mol
N-H bond energy = 386 kJ/mol
O-Br bond energy = 201 kJ/mol
Let's now calculate the energy change (∆H) for the reaction:
∆H = (1 × N-Br bond energy broken) - (3 × O-H bond energy broken) + (3 × H-O bond energy formed) + (1 × N-H bond energy formed) + (3 × O-Br bond energy formed)
∆H = (1 × 201 kJ/mol) - (3 × 459 kJ/mol) + (3 × 459 kJ/mol) + (1 × 386 kJ/mol) + (3 × 201 kJ/mol)
∆H = 201 kJ/mol - 1377 kJ/mol + 1377 kJ/mol + 386 kJ/mol + 603 kJ/mol
∆H = 81 kJ/mol
Therefore, using the given bond energy values and the calculation, the energy change (∆H) for the reaction is +81 kJ/mol.
Now, to answer your specific question, the strength of the N-Br bond is given by the N-Br bond energy, which is 201 kJ/mol.