Chapter 9, Problem 7STP

Interpretation Introduction

Interpretation:

H₂ reacts with O₂ and produced water vapors. The molecular picture of product and the left-over reactant needs to be determined.

Concept Introduction:

The reaction in which the reactant is totally consumed when the reaction is completed is

known as limiting reactant.

Answer to Problem 7STP

The left-over reactant is O₂ molecules.

Explanation of Solution

The given reaction is shown below:

  ${\text{H}}_{\text{2}}\left(\text{g}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)$

The balanced chemical reaction is shown below:

  ${\text{H}}_{\text{2}}\left(\text{g}\right)\text{+ }\frac{\text{1}}{\text{2}}{\text{O}}_{\text{2}}\left(\text{g}\right)\to {\text{ H}}_{\text{2}}\text{O}\left(\text{g}\right)$

H₂ molecule represented as follows:

  

O₂ molecules represented as follows:

  

The molecular picture is shown below:

  

As stochiometric coefficient defines the ratio in which reactant are reacting

According to the balanced reaction; 1 molecule of H₂ reacts with ½ molecule of O₂ and produces 1 molecule of H₂O. In the given picture there are 6 molecules of H₂ are present and 6 molecules of O₂ are present. Therefore; 6 molecules of H₂ reacts with 3 molecules of O2 but there are 6 molecules of O₂ present. So, H₂ act as a limiting reactant. Hence, 6 molecules of H₂ will react with 3 molecules of O₂ and will produce 6 molecule of water and the remaining 3 molecules of oxygen will be present as they don’t react.

Therefore; the left-over reactant is O₂.

The molecular picture is shown below:

  

Conclusion

The left-over reactant is O₂ molecules