Question

Predict the products that would result from each of the following reactions and balance: a. combination: \(\mathrm{Mg}(s)+\mathrm{Cl}_{2}(g) \longrightarrow\) b. decomposition: \(\mathrm{HBr}(g) \stackrel{\Delta}{\longrightarrow}\) c. single replacement: \(\mathrm{Mg}(s)+\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}(a q) \longrightarrow\) d. double replacement: \(\mathrm{K}_{2} \mathrm{~S}(a q)+\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(a q) \longrightarrow\) e. combustion: \(\mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \stackrel{\Delta}{\longrightarrow}\)

Short answer

a) \( \text{Mg}(s) + \text{Cl}_2(g) \rightarrow \text{MgCl}_2(s) \), b) \( 2\text{HBr}(g) \rightarrow \text{H}_2(g) + \text{Br}_2(g) \), c) \( \text{Mg}(s) + \text{Zn(NO}_3)_{2}(aq) \rightarrow \text{Mg(NO}_3)_{2}(aq) + \text{Zn}(s) \), d) \( \text{K}_2\text{S}(aq) + \text{Pb(NO}_3)_{2}(aq) \rightarrow 2\text{KNO}_3(aq) + \text{PbS}(s) \), e) \( 2\text{C}_2\text{H}_6(g) + 7\text{O}_2(g) \rightarrow 4\text{CO}_2(g) + 6\text{H}_2\text{O}(g) \).

Step-by-step solution

Combination Reaction

In a combination reaction, two or more reactants combine to form a single product. For the reaction \(\text{Mg}(s) + \text{Cl}_2(g) \rightarrow \), magnesium (Mg) will combine with chlorine gas (Cl\textsubscript{2}) to form magnesium chloride (MgCl\textsubscript{2}). Therefore, the balanced equation is \( \text{Mg}(s) + \text{Cl}_2(g) \rightarrow \text{MgCl}_2(s) \).

Decomposition Reaction

In a decomposition reaction, a compound breaks down into two or more simpler substances. For the reaction \( \text{HBr}(g) \rightarrow \), hydrogen bromide (HBr) will decompose into hydrogen gas (H\textsubscript{2}) and bromine gas (Br\textsubscript{2}) when heated (denoted by \( \Delta\)). The balanced equation is \( 2\text{HBr}(g) \rightarrow \text{H}_2(g) + \text{Br}_2(g) \).

Single Replacement Reaction

In a single replacement reaction, one element replaces another element in a compound. For the reaction \( \text{Mg}(s) + \text{Zn(NO}_3)_{2}(aq) \rightarrow \), magnesium (Mg) will replace zinc (Zn) in zinc nitrate (Zn(NO\textsubscript{3})\textsubscript{2}), resulting in the formation of magnesium nitrate (Mg(NO\textsubscript{3})\textsubscript{2}) and zinc metal (Zn). The balanced equation is \( \text{Mg}(s) + \text{Zn(NO}_3)_{2}(aq) \rightarrow \text{Mg(NO}_3)_{2}(aq) + \text{Zn}(s) \).

Double Replacement Reaction

In a double replacement reaction, the ions of two compounds exchange places to form two new compounds. For the reaction \( \text{K}_2\text{S}(aq) + \text{Pb(NO}_3)_{2}(aq) \rightarrow \), potassium sulfide (K\textsubscript{2}S) and lead(II) nitrate (Pb(NO\textsubscript{3})\textsubscript{2}) will react to form potassium nitrate (KNO\textsubscript{3}) and lead(II) sulfide (PbS). The balanced equation is \( \text{K}_2\text{S}(aq) + \text{Pb(NO}_3)_{2}(aq) \rightarrow 2\text{KNO}_3(aq) + \text{PbS}(s) \).

Combustion Reaction

In a combustion reaction, a hydrocarbon reacts with oxygen gas (O\textsubscript{2}), producing carbon dioxide (CO\textsubscript{2}) and water (H\textsubscript{2}O). For the reaction \( \text{C}_2\text{H}_6(g) + \text{O}_2(g) \rightarrow \), ethane (C\textsubscript{2}H\textsubscript{6}) will react with oxygen (O\textsubscript{2}) to form CO\textsubscript{2} and H\textsubscript{2}O. The balanced equation is \( 2\text{C}_2\text{H}_6(g) + 7\text{O}_2(g) \rightarrow 4\text{CO}_2(g) + 6\text{H}_2\text{O}(g) \).

Key concepts

Combination Reaction

In a combination reaction, two or more substances come together to form a single new substance. This is one of the simplest types of chemical reactions. Imagine it like combining two puzzle pieces to form one larger piece. For example, in the combination reaction given: \[ \mathrm{Mg}(s) + \mathrm{Cl}_{2}(g) \rightarrow \mathrm{MgCl}_{2}(s) \] solid magnesium reacts with chlorine gas to form magnesium chloride, a single product. Here, the reactants are magnesium (\( \mathrm{Mg} \)) and chlorine gas (\( \mathrm{Cl}_{2} \)), and the product is magnesium chloride (\( \mathrm{MgCl}_{2} \)). Combination reactions are common in nature and industrial processes.

Decomposition Reaction

A decomposition reaction takes place when one compound splits into two or more simpler substances. Think of it as breaking down a large brick into smaller pieces. For the decomposition reaction given: \[ 2\mathrm{HBr}(g) \rightarrow \mathrm{H}_{2}(g) + \mathrm{Br}_{2}(g) \] hydrogen bromide gas breaks into hydrogen gas and bromine gas when it's heated. \( \Delta \) indicates that heat is applied. Decomposition reactions are useful in extracting elements from their compounds and in recycling processes.

Single Replacement Reaction

In a single replacement reaction, one element swaps places with another in a compound. It's like a dance where one partner takes the place of another. For the reaction given: \[ \mathrm{Mg}(s) + \mathrm{Zn}(\mathrm{NO}_{3})_{2}(aq) \rightarrow \mathrm{Mg}(\mathrm{NO}_{3})_{2}(aq) + \mathrm{Zn}(s) \] solid magnesium displaces zinc in zinc nitrate, forming magnesium nitrate and zinc metal. The magnesium (\( \mathrm{Mg} \)) kicks out the zinc (\( \mathrm{Zn} \)), taking its place. Single replacement reactions are widely seen in metallurgy and in biological processes.

Double Replacement Reaction

In a double replacement reaction, the ions of two compounds exchange places to form two new compounds. Imagine two couples swapping partners at a dance party. For the reaction given: \[ \mathrm{K}_{2}\mathrm{S}(aq) + \mathrm{Pb}(\mathrm{NO}_{3})_{2}(aq) \rightarrow 2\mathrm{KNO}_{3}(aq) + \mathrm{PbS}(s) \] potassium sulfide reacts with lead(II) nitrate resulting in potassium nitrate and lead(II) sulfide. The ion exchange results in the formation of new products. These reactions often occur in aqueous solutions and are common in various fields such as biochemistry and environmental science.

Combustion Reaction

A combustion reaction involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water. These reactions release energy, often in the form of heat and light. For the combustion reaction: \[ 2\mathrm{C}_{2}\mathrm{H}_{6}(g) + 7\mathrm{O}_{2}(g) \rightarrow 4\mathrm{CO}_{2}(g) + 6\mathrm{H}_{2}\mathrm{O}(g) \] ethane reacts with oxygen to form carbon dioxide and water, releasing energy. Combustion reactions are fundamental to energy production, driving engines and generators, and providing heat in everyday life.