Chapter 2, Problem 11STP

Interpretation Introduction

Interpretation: The given table must be filled by identifying the respective missing masses using the law of conservation of mass.

Concept Introduction: In a chemical change, the chemical bonds present in reactants are broken to form elements that are then rearranged to form new chemical bonds resulting in the formation of products that possess different compositions than the reactants.

Answer to Problem 11STP

Mass of Magnesium (g)	Mass of Oxygen (g)	Mass of magnesium oxide (g)
5	3.30	8.3
6.5	4.30	10.8
13.6	9.00	22.60
19.00	12.50	31.5

Explanation of Solution

Given:

Mass of Magnesium (g)	Mass of Oxygen (g)	Mass of magnesium oxide (g)
5	3.30	8.3
6.5	(a)	10.8
13.6	9.00	(b)
(c)	12.50	31.5

According to the law of conservation of mass, mass is conserved in any chemical or physical change. The mass of reactants is always equal to the mass of products during any chemical reaction. So,

(a)

  $\begin{array}{l}{\text{mass of reactant (Mg + O}}_{\text{2}}\text{) = mass of product (MgO)}\\ \text{6}\text{.5 g + x g = 10}\text{.8 g}\\ \text{x g = 10}\text{.8 g - 6}\text{.5 g}\\ \text{x g = 4}\text{.3 g}\end{array}$

(b)

  $\begin{array}{l}{\text{mass of reactant (Mg + O}}_{\text{2}}\text{) = mass of product (MgO)}\\ \text{13}\text{.6 g + 9 g = y g}\\ \text{y g = 22}\text{.6 g}\end{array}$

(c)

  $\begin{array}{l}{\text{mass of reactant (Mg + O}}_{\text{2}}\text{) = mass of product (MgO)}\\ \text{z g + 12}\text{.5 g = 31}\text{.5 g}\\ \text{z g = 31}\text{.5 g - 12}\text{.5 g}\\ \text{z g = 19 g}\end{array}$

Therefore, the complete table is:

Mass of Magnesium (g)	Mass of Oxygen (g)	Mass of magnesium oxide (g)
5	3.30	8.3
6.5	4.30	10.8
13.6	9.00	22.60
19.00	12.50	31.5