Draw the lewis structure for the molecule ch3ch2cch. how many sigma and pi bonds does it contain?

             The structure of 1-Butyne is shown below and it contains;

                                         Nine Sigma Bonds

                                             Two Pi Bonds

Explanation:
                     In given structure the sigma bonds are highlighted with blue colour and pi bonds are highlighted by Black colour and indicated by red arrows.
                     Remember the very first covalent bond between two atoms is always the sigma bond. After formation of sigma bond if further p orbitals with unpaired electrons are available they will form pi bond, or two pi bonds as in given scenario.

Adozen is 1221/12 = 1.751.75 x 12 = 21therefore, 1.75 is the answer.