Problem 2 - Chemistry A Guided Inquiry

Question

How do the calculated bond orders for ethane, ethene, and ethyne compare to bond orders predicted by the Lewis structures?

Step-by-Step Solution

Answer

The bond orders predicted by the Lewis structures for ethane, ethene, and ethyne match the calculated bond orders. The bond order is 1 for ethane, 2 for ethene, and 3 for ethyne.

Step 1: Draw the Lewis Structure for Each Molecule

For the molecule ethane (CH3-CH3), each Carbon atom is bonded with three Hydrogen atoms and another Carbon atom. This forms four single bonds. So, the Lewis structure will show single bonds between all atoms. Ethene (CH2=CH2), each Carbon is bonded with two Hydrogens and another Carbon, creating one double bond (C=C) and four single bonds (C-H). Ethyne (CH≡CH), each Carbon is connected to a Hydrogen and another Carbon with a triple bond, resulting in two single bonds (C-H) and a triple bond (C-C).

Step 2: Predicte the Bond Order Using Lewis Structures

From the Lewis structures, predict bond orders by the number of shared electron pairs between two atoms: a single bond has bond order 1, a double bond has bond order 2, and a triple bond has bond order 3. Therefore, For ethane draw a single bond (C-C bond) and bond order 1, for ethene draw a double bond (C-C bond) and bond order 2, and for ethyne draw a triple bond (C-C bond) and bond order 3.

Step 3: Compare Calculated and Predicted Bond Order

Based on the nature of bonding in these compounds, the calculated and predicted bond orders are the same. The predicted bond order for ethane (1), ethene (2), and ethyne (3) from the Lewis structures matches the actual bond order. This implies that Lewis structures are a reliable method for predicting the bond order in these simple hydrocarbon molecules.