Chapter 7, Problem 25CR

Interpretation Introduction

(a)

Interpretation:

The given equation should be completed and balanced.

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{Pb(NO}}_{\text{3}}{\text{)}}_{\text{2(aq)}}{\text{ + Na}}_{\text{2}}{\text{S}}_{\text{(aq)}}\to {\text{ PbS}}_{\text{(s)}}{\text{ + 2NaNO}}_{\text{3(aq)}}$.

Explanation of Solution

This is a precipitation reaction in which PbS precipitate is formed. This is also a double displacement reaction which is the two reactants have exchanged their anions. In the unbalanced equation, ${\text{Pb(NO}}_{\text{3}}{\text{)}}_{\text{2(aq)}}{\text{ + Na}}_{\text{2}}{\text{S}}_{\text{(aq)}}\to {\text{ PbS}}_{\text{(s)}}{\text{ + NaNO}}_{\text{3(aq)}}$ number of Na atoms in reactants side is two, but one in the products side. So we place 2 before NaNO₃. Then the whole equation gets balanced. So the balanced equation is, ${\text{Pb(NO}}_{\text{3}}{\text{)}}_{\text{2(aq)}}{\text{ + Na}}_{\text{2}}{\text{S}}_{\text{(aq)}}\to {\text{ PbS}}_{\text{(s)}}{\text{ + 2NaNO}}_{\text{3(aq)}}$.

Interpretation Introduction

(b)

Interpretation:

The given equation should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{AgNO}}_{\text{3(aq)}}{\text{ + HCl}}_{\text{(aq)}}\to {\text{ AgCl}}_{\text{(s)}}{\text{ + HNO}}_{\text{3(aq)}}$.

Explanation of Solution

This is a precipitation reaction in which AgCl precipitate is formed. This is also a double displacement reaction which is the two reactants have exchanged their anions. The equation is already balanced.

Interpretation Introduction

(c)

Interpretation:

The given equation should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{2 Mg}}_{(s)}{\text{ + O}}_{2(g)}\to {\text{ 2 MgO}}_{(s)}$.

Explanation of Solution

This is a combustion reaction in which Mg is rapidly reacting with oxygen producing a flame and MgO solid. This is also an oxidation reduction reaction where Mg has oxidized and O₂ has reduced. In the unbalanced equation, ${\text{Mg}}_{(s)}{\text{ + O}}_{2(g)}\to {\text{ MgO}}_{(s)}$ number of O atoms in reactants side is two, but one in the products side. So we place 2 before MgO. Then number of Mg in products side becomes two. So we place 2 before Mg. So the balanced equation is, ${\text{2 Mg}}_{(s)}{\text{ + O}}_{2(g)}\to {\text{ 2 MgO}}_{(s)}$.

Interpretation Introduction

(d)

Interpretation:

The given equations should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{H}}_2{\text{SO}}_{4(aq)}{\text{ + 2 KOH}}_{(aq)}\to {\text{ K}}_2{\text{SO}}_{4(aq)}{\text{ + 2 H}}_2{\text{O}}_{(l)}$.

Explanation of Solution

This is an acid-base reaction in which H+ from the acid reacts with OH- from the base to form water. And ionic compound K₂ SO₄ salt is also formed. This is also a double displacement reaction. In the unbalanced equation, ${\text{H}}_2{\text{SO}}_{4(aq)}{\text{ + KOH}}_{(aq)}\to {\text{ K}}_2{\text{SO}}_{4(aq)}{\text{ + H}}_2{\text{O}}_{(l)}$ number of K atoms in the reactants side is one but two in the products side. So we place 2 before KOH. Then number of H atoms becomes four in the reactants side. So we place 2 before H₂ O. So the balanced equation is, ${\text{H}}_2{\text{SO}}_{4(aq)}{\text{ + 2 KOH}}_{(aq)}\to {\text{ K}}_2{\text{SO}}_{4(aq)}{\text{ + 2 H}}_2{\text{O}}_{(l)}$.

Interpretation Introduction

(e)

Interpretation:

The given equations should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{BaCl}}_{2(aq)}{\text{ + H}}_2{\text{SO}}_{4(aq)}\to {\text{ BaSO}}_{4(s)}{\text{ + 2 HCl}}_{(aq)}$.

Explanation of Solution

This is a precipitation reaction in which BaSO₄ precipitate is formed. This is also a double displacement reaction which the two reactants have exchange their anions. In the unbalanced equation, ${\text{BaCl}}_{2(aq)}{\text{ + H}}_2{\text{SO}}_{4(aq)}\to {\text{ BaSO}}_{4(s)}{\text{ + HCl}}_{(aq)}$ number of Cl atoms in reactants side is two, but one in the products side. So we place 2 before HCl. Then the whole reaction becomes balanced. So the balanced equation is, ${\text{BaCl}}_{2(aq)}{\text{ + H}}_2{\text{SO}}_{4(aq)}\to {\text{ BaSO}}_{4(s)}{\text{ + 2 HCl}}_{(aq)}$.

Interpretation Introduction

(f)

Interpretation:

The given equations should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{Mg}}_{(s)}{\text{ + H}}_2{\text{SO}}_{4(aq)}\to {\text{ MgSO}}_{4(aq)}{\text{ + H}}_{2(g)}$.

Explanation of Solution

This is a single displacement reaction because Mg has replaced the H atoms in sulfuric acid. This is also an Oxidation reduction reaction where Mg has oxidized and H has reduced. The equation is already balanced.

Interpretation Introduction

(g)

Interpretation:

The given equations should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{2 Na}}_3{\text{PO}}_{3(aq)}{\text{ + 3 CaCl}}_{2(aq)}\to {\text{ Ca}}_3{{\text{(PO}}_4\text{)}}_{2(s)}{\text{ + 6 NaCl}}_{(aq)}$.

Explanation of Solution

This is a single precipitation reaction in which Ca₃ (PO₄ )₂ precipitate is formed. This is also a double displacement reaction. In the unbalanced equation, ${\text{Na}}_3{\text{PO}}_{3(aq)}{\text{ + CaCl}}_{2(aq)}\to {\text{ Ca}}_3{{\text{(PO}}_4\text{)}}_{2(s)}{\text{ + NaCl}}_{(aq)}$ number of Ca atoms in the products side is three but one in the reactants side. So we place 3 before CaCl₂. Then number of Cl atoms in the reactants side becomes six. So we place 6 before NaCl. Then number of Na atoms in the products side becomes six. So we place 2 before Na₃ PO₃. So the balanced equation is, ${\text{2 Na}}_3{\text{PO}}_{3(aq)}{\text{ + 3 CaCl}}_{2(aq)}\to {\text{ Ca}}_3{{\text{(PO}}_4\text{)}}_{2(s)}{\text{ + 6 NaCl}}_{(aq)}$.

Interpretation Introduction

(h)

Interpretation:

The given equations should be completed and balanced

Concept Introduction:

Deciding which products will form when two or more reactants added together is not an easy task without any experimental evidences. The best way to predict what products will form is to think of various possibilities and then decide which product is most likely to form.

Answer to Problem 25CR

${\text{2 C}}_4{\text{H}}_{10(l)}{\text{ + 13 O}}_{2(g)}\to {\text{ 8 CO}}_{2(g)}{\text{ + 10 H}}_2{\text{O}}_{(g)}$.

Explanation of Solution

This is a combustion reaction in which C₄ H_{1 0} reacts with oxygen. This is also an oxidation reduction reaction where C₄ H_{1 0} is oxidized and O₂ is reduced. In the unbalanced equation, ${\text{C}}_4{\text{H}}_{10(l)}{\text{ + O}}_{2(g)}\to {\text{ CO}}_{2(g)}{\text{ + H}}_2{\text{O}}_{(g)}$ number of C atoms in the reactants side is four, but one in the products side. So we place 4 before CO₂. Number of H atoms in the reactants side is 10, but only two in the products side. So we place 5 before H₂ O. Then number of O atoms in the products side becomes thirteen. So we place 13/2 before O₂. But we cannot keep a half integer in a balanced chemical equation. So we multiply the whole equation by two. So the balanced equation is, ${\text{2 C}}_4{\text{H}}_{10(l)}{\text{ + 13 O}}_{2(g)}\to {\text{ 8 CO}}_{2(g)}{\text{ + 10 H}}_2{\text{O}}_{(g)}$.