Answer
The molecular formula is $C_5H_{10}O$.
For the lewis structure: Draw a carbon wherever two lines meet and, a line begins and ends. Draw the two lines as double bond. And then add the number of hydrogens so that each carbon has four bonds.
Work Step by Step
1) Draw a carbon wherever two lines meet and, a line begins and ends.
2) Draw a double bond with O and two lone pairs on O.
3) Then add the hydrogens so that each carbon has four bonds.
4) Count the number of C, H and O. In this structure there are 5 Carbons, 10 hydrogens and 1 Oxygen. Thus, the molecular formula is $C_5H_{10}O$.
