Chapter 12.2, Problem 25LC

Interpretation Introduction

Interpretation: The statement that stoichiometric calculations are not possible without a balanced chemical equation needs to be explained.

Concept introduction: A balanced chemical equation is an equation in which the number of atoms of each species of reactants is equal to the number of atoms of each species of products.

Answer to Problem 25LC

The equation must be balanced in the stoichiometric calculation because mass is always conserved in any reaction.

Explanation of Solution

In a reaction, all reactants react together in a stoichiometric ratio to form a product which is also formed according to stoichiometry.

For example:

  $2{\text{H}}_2+{\text{O}}_2\to 2{\text{H}}_{\text{2}}\text{O}$

• In stoichiometric calculation, the first step is to balance the equation. This is because mass is always conserved in a reaction. According to the law of conservation of mass, mass can neither be created nor destroyed.
• If the equation is not balanced, the mole ratio conversion cannot be done and hence, the stoichiometric calculations cannot be done.

Conclusion

The equation must be balanced in the stoichiometric calculation because mass is always conserved in any reaction.