Question

Would you predict that the C−O bond lengths in the formate ion would be longer or shorter relative to those in CO2?

Answer 1

The Lewis structures for formate ion and carbon dioxide are shown in the attached pictures. As you can see, the formate ion consists of one C=O bond and one C-O bond, while carbon dioxide has two C=O bonds. Double bonds are weaker, hence, longer compared to single bonds. Therefore, the C-O bonds in the formate ion is shorter than those in carbon dioxide.