Chapter 9, Problem 12A

Interpretation Introduction

Interpretation:

The meaning for the statement that balanced chemical equation describes the stoichiometry of the reaction needs to be explained.

Concept Introduction:

• A chemical reaction is represented in terms of a chemical equation with the reactants on the left and the products on the right

  $\text{Reactants }\to \text{ Products}$

• The coefficient of a balanced chemical equation i.e. the stoichiometry gives the amount of reactants and products involved in the reaction.

Answer to Problem 12A

A balanced chemical equation describes the amounts of reactants and products in terms of the stoichiometric coefficients.

Explanation of Solution

'Stoichiometry' is a term that refers to the amount or measure of elements. For balanced chemical equations, 'stoichiometry' helps to establish a correct relation between the amounts of reactants and products, in terms of a mole-mole ratio. Hence, it can be used to determine the amount of products formed from a known quantity of reactants.

For example consider the formation of ammonia (NH₃) from N₂ and H₂. The reaction is:

  ${\text{N}}_{\text{2}}{\text{(g) + H}}_{\text{2}}(\text{g})\to {\text{NH}}_{\text{3}}(\text{g})$

The balanced equation is:

  ${\text{N}}_{\text{2}}{\text{(g) + 3H}}_{\text{2}}(\text{g})\to 2{\text{NH}}_{\text{3}}(\text{g})$

As per the reaction stoichiometry:

1 mole of N₂ reacts with 3 moles of H₂ to form 2 moles of NH₃

Conclusion

Therefore, the relative amounts of reactants and products can be identified from the reaction stoichiometry.