The equation below shows the incomplete combustion of ethene.

C2H4 + O2 → CO2 + H2O

If 2.70 mol C2H4 is reacted with 6.30 mol O2 identify the limiting reagent

The limiting reagent is O₂.

Firstly, write the balanced chemical equation:

C₂H₄ + O₂ → CO₂ + H₂O

Then, we need to write the mole ratio of the reactants

The theoretical mole ratio is given by the coefficients of the balanced chemical equation: 3 moles of O₂ react with 1 mol of C₂H₄

Now, let's write the mole ratio of the substances available

 ≈  

We concluded that,

Since, the ratio of the O₂ to C₂H₄ available is less than the theoretical ratio of O₂ needed to react with C₂H₄, the former is not enough: it will be consumed before the other reagent and it is the limiting reactant.

Hence, the limiting reagent is O₂.

Learn more:

link

Explanation:

1. Write the balanced molecular equation:

2. Write the mole ratio of the reactants

The theoretical mole ratio is given by the coefficients of the balanced molecula equation: 3 moles of O₂ react with 1 mol of C₂H₄

3. Write the mole ratio of the substances available

4. Conclusion

Since the ratio of the O₂ to C₂H₄ available is less than the theoretical ratio of O₂ needed to react with C₂H₄, the former is not enough: it will be consumed before the other reagent and it is the limiting reactant.

Hence, the limiting reagent is O₂.