2H2 + O2 yield 2H2O
to calculate bond enthalpy, we have to take bond breaking minus bond making, how do we know which one is bond breaking and bond making
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To determine which bonds are being broken and which bonds are being formed in a chemical reaction, you can follow these general steps:
1. Write the balanced chemical equation for the reaction.
2H2 + O2 → 2H2O
2. Identify the bonds present in the reactants and products.
Reactants: H-H (hydrogen), O=O (oxygen)
Products: O-H (oxygen-hydrogen)
3. Compare the bonds between the reactants and products to determine which bonds are being broken and which bonds are being formed.
In this reaction:
- The bond between two hydrogen atoms (H-H) in the reactant (2H2) is being broken.
- The bond between two oxygen atoms (O=O) in the reactant (O2) is also being broken.
- The bonds between an oxygen atom and a hydrogen atom (O-H) in the product (2H2O) are being formed.
Remember that bond breaking requires energy input, while bond formation releases energy. Bond enthalpy calculations involve subtracting the energy required to break the bonds from the energy released when new bonds are formed.
In order to calculate bond enthalpy in a reaction, we need to identify the bonds that are broken and formed during the reaction. Bond enthalpy refers to the amount of energy required to break a specific bond or the energy released when a bond is formed.
To determine which bonds are broken and which ones are formed, we can examine the chemical equation. In the case of the reaction you mentioned:
2H2 + O2 → 2H2O
We start with two molecules of dihydrogen (H2) and one molecule of dioxygen (O2), and end up with two molecules of water (H2O).
The arrow in the chemical equation indicates the direction of the reaction, showing the bonds breaking and forming. In this case, the reactants (H2 and O2) are on the left side of the arrow, and the products (H2O) are on the right side.
To determine bond breaking, we look at the reactants. In this reaction, the H-H bonds in the H2 molecule and the O=O bonds in the O2 molecule are broken. Breaking bonds requires energy, so the energy associated with these bonds is positive.
To determine bond making, we look at the products. In this reaction, the O-H bonds are formed in the H2O molecule. Forming bonds releases energy, so the energy associated with these bonds is negative.
To calculate the overall bond enthalpy for the reaction, we subtract the energy associated with bond breaking from the energy associated with bond making. The equation for calculating bond enthalpy would look like:
ΔH = Σ(ΔH(bonds broken)) - Σ(ΔH(bonds formed))
Note that bond enthalpies are average values since they can vary depending on the specific molecular environment. Therefore, it's important to use average bond enthalpy values obtained from experimental data when performing calculations.