Chapter 7, Problem 36A

(a)

Interpretation Introduction

Interpretation:

The given chemical equation needs to be balanced.

  ${\text{CaF}}_2\left(s\right)+{\text{H}}_2{\text{SO}}_4\left(l\right)\to {\text{CaSO}}_4\left(s\right)+\text{HF}\left(g\right)$

Concept Introduction:

In a balanced equation, there are equal numbers of atoms of the elements on the reactant and the product side. This is due to the law of conservation of mass which states that matter can neither be created nor destroyed, but may be transformed from one form into another.

Answer to Problem 36A

The balanced chemical equation is

  ${\text{CaF}}_2\left(s\right)+{\text{H}}_2{\text{SO}}_4\left(l\right)\to {\text{CaSO}}_4\left(s\right)+2\text{ HF}\left(g\right)$

Explanation of Solution

The given reaction is a double decomposition reaction.

  ${\text{CaF}}_2\left(s\right)+{\text{H}}_2{\text{SO}}_4\left(l\right)\to {\text{CaSO}}_4\left(s\right)+\text{HF}\left(g\right)$

In order to balance the number of fluorine, F atoms on both sides, multiply hydrogen fluoride, $\text{HF}$ on the right by 2.

  ${\text{CaF}}_2\left(s\right)+{\text{H}}_2{\text{SO}}_4\left(l\right)\to {\text{CaSO}}_4\left(s\right)+2\text{ HF}\left(g\right)$

A quick inspection indicates that all there are equal numbers of atoms on both sides of the equation and hence, the reaction is balanced.

This trial and error approach works for simple equations; however, for more complex reactions, a proper method like the ion electron method must be used.

(b)

Interpretation Introduction

Interpretation:

The given chemical equation needs to be balanced.

  $\text{KBr}\left(s\right)+{\text{H}}_3{\text{PO}}_4\left(aq\right)\to {\text{K}}_3{\text{PO}}_4\left(aq\right)+\text{HBr}\left(g\right)$

Concept Introduction:

The law of conservation of mass indicates that all the atoms in a chemical reaction must be balanced.

Answer to Problem 36A

The balanced chemical equation is

  $\text{3 KBr}\left(s\right)+{\text{H}}_3{\text{PO}}_4\left(aq\right)\to {\text{K}}_3{\text{PO}}_4\left(aq\right)+\text{3 HBr}\left(g\right)$

Explanation of Solution

The unbalanced reaction is given as

  $\text{KBr}\left(s\right)+{\text{H}}_3{\text{PO}}_4\left(aq\right)\to {\text{K}}_3{\text{PO}}_4\left(aq\right)+\text{HBr}\left(g\right)$

In order to balance the number of potassium (K) atoms on both sides, multiply $\text{K}$ on the left by 3.

  $\text{3 KBr}\left(s\right)+{\text{H}}_3{\text{PO}}_4\left(aq\right)\to {\text{K}}_3{\text{PO}}_4\left(aq\right)+\text{HBr}\left(g\right)$

Next balance the number of bromine, Br atoms on both sides.

  $\text{3 KBr}\left(s\right)+{\text{H}}_3{\text{PO}}_4\left(aq\right)\to {\text{K}}_3{\text{PO}}_4\left(aq\right)+\text{3 HBr}\left(g\right)$

Check that there are equal numbers of atoms of all the elements on both sides and hence, the reaction is balanced.

(c)

Interpretation Introduction

Interpretation:

The given chemical equation needs to be balanced.

  ${\text{TiCl}}_4\left(l\right)+\text{Na}\left(s\right)\to \text{NaCl}\left(s\right)+\text{Ti}\left(s\right)$

Concept Introduction:As per the law of conservation of mass, there must be equal numbers of atoms of all the elements in a balanced chemical equation.

Answer to Problem 36A

The balanced chemical equation is

  ${\text{TiCl}}_4\left(l\right)+4\text{ Na}\left(s\right)\to \text{4 NaCl}\left(s\right)+\text{Ti}\left(s\right)$

Explanation of Solution

The unbalanced reaction is

  ${\text{TiCl}}_4\left(l\right)+\text{Na}\left(s\right)\to \text{NaCl}\left(s\right)+\text{Ti}\left(s\right)$

There are four chlorine, Cl atoms on the left and only one on the right. In order to balance the number of Cl atoms, multiply sodium chloride, $\text{NaCl}$ on the right by 4.

  ${\text{TiCl}}_4\left(l\right)+\text{Na}\left(s\right)\to 4\text{ NaCl}\left(s\right)+\text{Ti}\left(s\right)$

In order to balance the number of sodium, Na atoms on both sides, multiply Na on the left by 4.

  ${\text{TiCl}}_4\left(l\right)+4\text{ Na}\left(s\right)\to 4\text{ NaCl}\left(s\right)+\text{Ti}\left(s\right)$

The reaction has equal numbers of atoms of the elements on both sides and hence, the reaction is balanced.

(d)

Interpretation Introduction

Interpretation:

The given chemical equation needs to be balanced.

  ${\text{K}}_2{\text{CO}}_3\left(s\right)\to {\text{K}}_2\text{O}\left(s\right)+{\text{CO}}_2\left(g\right)$

Concept Introduction:

The law of conservation of mass states that there are equal numbers of atoms on the reactant and the product side of a balanced chemical equation.

Answer to Problem 36A

The balanced chemical equation is

  ${\text{K}}_2{\text{CO}}_3\left(s\right)\to {\text{K}}_2\text{O}\left(s\right)+{\text{CO}}_2\left(g\right)$

Explanation of Solution

The unbalanced chemical equation is

  ${\text{K}}_2{\text{CO}}_3\left(s\right)\to {\text{K}}_2\text{O}\left(s\right)+{\text{CO}}_2\left(g\right)$

Note that there are equal numbers of atoms on both sides of the reaction and hence, the reaction is already balanced.