Chapter 2, Problem 2.32E

A flammable gas is known to contain only carbon and hydrogen. Its molecular weight is determined and found to be $28.05\text{u}$. Which of the following is the likely identity of the gas? Acetylene $\left({\text{C}}_{\text{2}}{\text{H}}_{\text{2}}\right)$, ethylene $\left({\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\right)$, ethane $\left({\text{C}}_{\text{2}}{\text{H}}_{\text{6}}\right)$.