Chapter 7, Problem 12STP

Interpretation Introduction

Interpretation:

A balanced chemical equation corresponding to the reaction between calcium metal and oxygen gas needs to be presented.

Concept Introduction:

• A chemical reaction is expressed as a chemical equation having reactants and products on left and right side of the reaction arrow respectively.

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

• A balanced chemical equation is one in which the number of atoms of various elements on the reactants side is equal to that on the product side. It depicts the stoichiometry of a given reaction.

• The equations are balanced in two steps:

1) Balance the atoms by matching the number of atoms of each type on the reactants and product side.

2) Adjust the coefficients to the smallest whole number. A coefficient of '1' is implied and therefore not explicitly written.

Answer to Problem 12STP

  ${\text{2Ca(s) + O}}_{\text{2}}(\text{g})\stackrel{\text{heat}}{\to }\text{2CaO (s)}$

Explanation of Solution

The given process involves the reaction between calcium metal and oxygen gas to produce solid calcium oxide. The reactants and products are:

Reactants:

  $\begin{array}{l}\text{Calcium, solid - Ca(s)}\\ {\text{Oxygen, gas - O}}_{\text{2}}\text{(g)}\end{array}$

Products:

  $\text{Calcium oxide, solid - CaO }(\text{s})$

Unbalanced equation:

  ${\text{Ca(s) + O}}_{\text{2}}(\text{g})\stackrel{\text{heat}}{\to }\text{CaO (s)}$

The above equation is not balanced since the number of O atoms is 2 on the reactants and 1 on the products side. In order to balance the above equation, multiply both Ca and CaO by 2 to get:

  ${\text{2Ca(s) + O}}_{\text{2}}(\text{g})\stackrel{\text{heat}}{\to }\text{2CaO (s)}$

Conclusion

Therefore, 2 moles of calcium reacts with 1 mole of oxygen to form 2 moles of calcium oxide.