Answer:
a).
[tex]2 \: moles \: of \: ethane \: react \: with \: 7 \: moles \: of \: oxygen \\ 24 \: moles \: react \: with \: ( \frac{24 \times 7}{2} ) \: moles \\ = 84 \: moles[/tex]
b).
[tex]2 \: moles \: react \: with \: 7 \: moles \\ ( \frac{12 \times 2}{7} ) \: moles \: react \: with \: 12 \: moles \\ = 3 .43 \: moles \\ 1 \: mole \: weighs \: 30 \: g \\ 3.43 \: moles \: weigh \: (3.43 \times 30) \\ = 102.9 \: g[/tex]
c).
746.7 g