Chapter 11, Problem 67E

Interpretation Introduction

(a)

Interpretation:

The balanced chemical equation for the reaction between propene and oxygen gas is to be stated.

Concept introduction:

A chemical reaction is a process in which rearrangement of atom or ions takes place between two reacting species. A balanced chemical equation represents an equation in which all the reactants and products are written with their stoichiometric coefficients and physical states. The number of atoms of an element on both sides of the equation is equal.

Answer to Problem 67E

The balanced chemical equation for the reaction between propene and oxygen gas is shown below.

${\text{2C}}_{\text{3}}{\text{H}}_{\text{6}}\left(g\right)+9{\text{O}}_2\left(g\right)\stackrel{\text{spark}}{\to }{\text{6CO}}_{\text{2}}\left(g\right)+6{\text{H}}_{\text{2}}\text{O}\left(g\right)$

Explanation of Solution

Hydrocarbons in the presence of oxygen burns to give carbon dioxide and water. Therefore, propene reacts with oxygen to give carbon dioxide and water.

The unbalanced chemical equation for the reaction between propene and oxygen gas is as shown below.

${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\left(g\right)+{\text{O}}_2\left(g\right)\stackrel{\text{spark}}{\to }{\text{CO}}_{\text{2}}\left(g\right)+{\text{H}}_{\text{2}}\text{O}\left(g\right)$

The numbers of atoms of elements on the left side of the reaction are not equal to the right side of the reaction. Therefore, the reaction is unbalanced.

Propene is multiplied by the coefficient two, oxygen gas by nine. On the right side, carbon dioxide and water both are multiplied by six.

Therefore, the balanced chemical equation for the reaction between propene and water is shown below.

${\text{2C}}_{\text{3}}{\text{H}}_{\text{6}}\left(g\right)+9{\text{O}}_2\left(g\right)\stackrel{\text{spark}}{\to }{\text{6CO}}_{\text{2}}\left(g\right)+6{\text{H}}_{\text{2}}\text{O}\left(g\right)$

The numbers of atoms of each element on the left side of the reaction are equal to the right side of the reaction. Therefore, the reaction is balanced.

Conclusion

The balanced chemical equation for the reaction between propene and oxygen gas has been stated.

Interpretation Introduction

(b)

Interpretation:

The balanced chemical equation for the heating of hydrated salt of sodium dichromate is to be stated.

Concept introduction:

A chemical reaction is a process in which rearrangement of atom or ions takes place between two reacting species. A balanced chemical equation represents an equation in which all the reactants and products are written with their stoichiometric coefficient and physical states. The number of atoms of an element on both sides of the equation is equal.

Answer to Problem 67E

The balanced chemical equation for the heating of hydrated salt of sodium dichromate is shown below.

${\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\cdot 2{\text{H}}_{\text{2}}\text{O}\left(s\right)\stackrel{\Delta }{\to }{\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\left(s\right)+2{\text{H}}_{\text{2}}\text{O}\left(g\right)$

Explanation of Solution

A hydrated salt on heating gives an anhydrous compound as on heating the water molecules evaporate. Therefore, on heating of sodium dichromate dihydrate, anhydrous sodium dichromate is obtained and water evaporates.

The completed chemical equation of the reaction for the heating of hydrated salt of sodium dichromate is shown below.

${\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\cdot 2{\text{H}}_{\text{2}}\text{O}\left(s\right)\stackrel{\Delta }{\to }{\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\left(s\right)+{\text{H}}_{\text{2}}\text{O}\left(g\right)$

The numbers of atoms of elements on the left side of the reaction are not equal to the right side of the reaction. Therefore, the reaction is unbalanced.

Water molecule is multiplied by two for balancing the equation.

Therefore, the balanced chemical equation for the reaction for the heating of hydrated salt of sodium dichromate is shown below.

${\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\cdot 2{\text{H}}_{\text{2}}\text{O}\left(s\right)\stackrel{\Delta }{\to }{\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\left(s\right)+2{\text{H}}_{\text{2}}\text{O}\left(g\right)$

The numbers of atoms of each element on the left side of the reaction are equal to the right side of the reaction. Therefore, the reaction is balanced.

Conclusion

The balanced chemical equation of the reaction between ${\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\cdot 2{\text{H}}_{\text{2}}\text{O}\left(s\right)\stackrel{\Delta }{\to }{\text{Na}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}\left(s\right)+2{\text{H}}_{\text{2}}\text{O}\left(g\right)$

Interpretation Introduction

(c)

Interpretation:

The balanced chemical equation for the reaction between hydrogen fluoride with calcium hydroxide is to be stated.

Concept introduction:

A chemical reaction is a process in which rearrangement of atom or ions takes place between two reacting species. A balanced chemical equation represents an equation in which all the reactants and products are written with their stoichiometric coefficient and physical states. The number of atoms of an element on both sides of the equation is equal.

Answer to Problem 67E

The balanced chemical equation for the reaction between hydrogen fluoride and calcium hydroxide is shown below.

$\text{2HF}\left(aq\right)+\text{Ca}{\left(\text{OH}\right)}_{\text{2}}\left(aq\right)\to {\text{CaF}}_{\text{2}}\left(aq\right)+2{\text{H}}_{\text{2}}\text{O}\left(l\right)$

Explanation of Solution

Acids and bases react to form water and salt. Hydrogen fluoride is an acid and calcium hydroxide is bases, they both react to form a salt of calcium and fluoride and also release water.

The unbalanced chemical equation for the reaction between hydrogen fluoride and calcium hydroxide is shown below.

$\text{HF}\left(aq\right)+\text{Ca}{\left(\text{OH}\right)}_{\text{2}}\left(aq\right)\to {\text{CaF}}_{\text{2}}\left(aq\right)+{\text{H}}_{\text{2}}\text{O}\left(l\right)$

The numbers of atoms of elements on the left side of the reaction are not equal to the right side of the reaction. Therefore, the reaction is unbalanced.

A coefficient of $2$ is placed in front of $\text{HF}$ a coefficient of $2$ is placed in front of ${\text{H}}_{\text{2}}\text{O}$ to balance the chemical equation.

Therefore, the balanced chemical equation for the reaction between hydrogen fluoride and calcium hydroxide is shown below.

$\text{2HF}\left(aq\right)+\text{Ca}{\left(\text{OH}\right)}_{\text{2}}\left(aq\right)\to {\text{CaF}}_{\text{2}}\left(aq\right)+2{\text{H}}_{\text{2}}\text{O}\left(l\right)$

The numbers of atoms of each element on the left side of the reaction are equal to the right side of the reaction. Therefore, the reaction is balanced.

Conclusion

The balanced chemical equation for the reaction between hydrogen fluoride and calcium hydroxide is stated above.