Chapter 11.1, Problem 10SSC

Interpretation Introduction

Interpretation:

The mole ratios for the given reaction of oxygen gas and hydrogen gas needs to be determined. And a sketch showing the reaction between six hydrogen molecules and oxygen molecules to form water molecules should be drawn.

Concept introduction:

The ratio of mass of substance to its molar mass is said to be number of moles of that substance.

The ratio of amount of any two compounds involved in a chemical reaction in terms of mole is said to be mole ratio, and used as a conversion factor between reactants and products.

Answer to Problem 10SSC

The mole ratios for the given reaction of oxygen gas and hydrogen gas is:

$\frac{{\text{2 mol of H}}_{\text{2}}\text{(g) }}{{\text{1 mol of O}}_{\text{2}}\text{(g) }};\frac{{\text{1 mol of O}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{(g) }}$, $\frac{{\text{2 mol of H}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{O(g) }};\frac{{\text{2 mol of H}}_{\text{2}}\text{O(g) }}{{\text{2 mol of H}}_{\text{2}}\text{(g) }}$ and $\frac{{\text{1 mol of O}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{O(g) }};\frac{{\text{2 mol of H}}_{\text{2}}\text{O(g) }}{{\text{1 mol of O}}_{\text{2}}\text{(g) }}$.

The sketch showing the reaction between six hydrogen molecules and oxygen molecules to form water molecules is:

Explanation of Solution

Given:

The balanced reaction between hydrogen gas and oxygen gas for the formation of water is:

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

From the given balanced chemical reaction, the mole ratio of ${\text{H}}_{\text{2}}$ and ${\text{O}}_{\text{2}}$ is 2:1 that means 2 moles of ${\text{H}}_{\text{2}}$ reacts with 1 mol of ${\text{O}}_{\text{2}}$, the mole ratio of ${\text{H}}_{\text{2}}$ and ${\text{H}}_2\text{O}$ is 2:2 that is 1:1 which means 1 mole of ${\text{H}}_{\text{2}}$ produces 1 mole of ${\text{H}}_2\text{O}$ and the mole ratio of ${\text{O}}_{\text{2}}$ and ${\text{H}}_2\text{O}$ is 1:2 that means 1 mole of ${\text{O}}_{\text{2}}$ produces 2 moles of ${\text{H}}_2\text{O}$.

Thus, the mole ratios for the reaction of oxygen gas and hydrogen gas is:

$\frac{{\text{2 mol of H}}_{\text{2}}\text{(g) }}{{\text{1 mol of O}}_{\text{2}}\text{(g) }};\frac{{\text{1 mol of O}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{(g) }}$, $\frac{{\text{2 mol of H}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{O(g) }};\frac{{\text{2 mol of H}}_{\text{2}}\text{O(g) }}{{\text{2 mol of H}}_{\text{2}}\text{(g) }}$ and $\frac{{\text{1 mol of O}}_{\text{2}}\text{(g) }}{{\text{2 mol of H}}_{\text{2}}\text{O(g) }};\frac{{\text{2 mol of H}}_{\text{2}}\text{O(g) }}{{\text{1 mol of O}}_{\text{2}}\text{(g) }}$.

Now, in order to make sketch the number of molecules of oxygen reacting with six molecules of hydrogen and the produced molecules of water is calculated from the mole ratio as it is also the molecular ratio.

The molecule ratio between ${\text{H}}_{\text{2}}$ and ${\text{O}}_{\text{2}}$ is 2:1 that means 2 molecules of ${\text{H}}_{\text{2}}$ reacts with 1 molecule of ${\text{O}}_{\text{2}}$ so, the number of ${\text{O}}_{\text{2}}$ molecule reacted with 6 ${\text{H}}_{\text{2}}$ molecule is:

${\text{6 molecule of H}}_{\text{2}}\text{(g) }\times \frac{{\text{1 molecule of O}}_{\text{2}}\text{(g) }}{{\text{2 molecule of H}}_{\text{2}}\text{(g) }}{\text{ = 3 molecule of O}}_{\text{2}}\text{(g)}$

The molecule ratio between ${\text{H}}_{\text{2}}$ and ${\text{H}}_2\text{O}$ is 2:2 that means 2 molecules of ${\text{H}}_{\text{2}}$ reacts to produce 2 molecule of ${\text{H}}_2\text{O}$ so, the number of ${\text{H}}_2\text{O}$ molecule produced from 6 ${\text{H}}_{\text{2}}$ molecule is:

${\text{6 molecule of H}}_{\text{2}}\text{(g) }\times \frac{{\text{2 molecule of H}}_2\text{O(g) }}{{\text{2 molecule of H}}_{\text{2}}\text{(g) }}{\text{ = 6 molecule of H}}_2\text{O(g)}$

Thus, 6 molecules of hydrogen gas react with 3 molecules of oxygen gas to produce 6 molecules of water as depicted in the below sketch, where white spheres represent H atoms and grey spheres represent O atoms: