Question

Predict the products that would result from each of the following reactions and balance: a. combination: \(\mathrm{Ca}(s)+\mathrm{O}_{2}(g) \longrightarrow\) b. combustion: \(\mathrm{C}_{6} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \stackrel{\Delta}{\longrightarrow}\) c. decomposition: \(\mathrm{PbO}_{2}(s) \stackrel{\Delta}{\longrightarrow}\) d. single replacement: \(\mathrm{KI}(s)+\mathrm{Cl}_{2}(g) \longrightarrow\) e. double replacement: \(\mathrm{CuCl}_{2}(a q)+\mathrm{Na}_{2} \mathrm{~S}(a q) \longrightarrow\)

Short answer

a=\(2\mathrm{CaO}\), b=\(12\mathrm{CO}_{2}\) and \(6\mathrm{H}_{2}\mathrm{O}\), c=\(2\mathrm{PbO}\) and \(\mathrm{O}_{2}\), d=\(2\mathrm{KCl}\) and \(\mathrm{I}_{2}\), e=\(\mathrm{CuS}\) and \(2\mathrm{NaCl}\).

Step-by-step solution

Combination Reaction

Predict the product for the reaction: \(\mathrm{Ca}(s) + \mathrm{O}_{2}(g) \longrightarrow\). Calcium (Ca) reacts with oxygen (O2) to form calcium oxide (CaO).Balanced Equation: \(2\mathrm{Ca}(s) + \mathrm{O}_{2}(g) \longrightarrow 2\mathrm{CaO}(s)\).

Combustion Reaction

Predict the product for the reaction: \(\mathrm{C}_{6}\mathrm{H}_{6}(g) + \mathrm{O}_{2}(g) \stackrel{\Delta}{\longrightarrow}\). Benzene (C6H6) combusts in the presence of oxygen to produce carbon dioxide (CO2) and water (H2O).Balanced Equation: \(2\mathrm{C}_{6}\mathrm{H}_{6}(g) + 15\mathrm{O}_{2}(g) \longrightarrow 12\mathrm{CO}_{2}(g) + 6\mathrm{H}_{2}\mathrm{O}(g)\).

Decomposition Reaction

Predict the product for the reaction: \(\mathrm{PbO}_{2}(s) \stackrel{\Delta}{\longrightarrow}\). Lead(IV) oxide decomposes upon heating to form lead(II) oxide (PbO) and oxygen gas (O2).Balanced Equation: \(2\mathrm{PbO}_{2}(s) \stackrel{\Delta}{\longrightarrow} 2\mathrm{PbO}(s) + \mathrm{O}_{2}(g)\).

Single Replacement Reaction

Predict the product for the reaction: \(\mathrm{KI}(s) + \mathrm{Cl}_{2}(g) \longrightarrow\). Chlorine (Cl2) replaces iodine (I) in potassium iodide (KI) to form potassium chloride (KCl) and iodine (I2).Balanced Equation: \(2\mathrm{KI}(s) + \mathrm{Cl}_{2}(g) \longrightarrow 2\mathrm{KCl}(s) + \mathrm{I}_{2}(s)\).

Double Replacement Reaction

Predict the product for the reaction: \(\mathrm{CuCl}_{2}(aq) + \mathrm{Na}_{2}\mathrm{S}(aq) \longrightarrow\). Copper(II) chloride (CuCl2) reacts with sodium sulfide (Na2S) to form copper(II) sulfide (CuS) and sodium chloride (NaCl).Balanced Equation: \(\mathrm{CuCl}_{2}(aq) + \mathrm{Na}_{2}\mathrm{S}(aq) \longrightarrow \mathrm{CuS}(s) + 2\mathrm{NaCl}(aq)\).

Key concepts

Combination Reaction

A combination reaction is when two or more substances combine to form a single product.
These reactions generally release energy and are crucial in the formation of many compounds.
For example, when calcium (Ca) reacts with oxygen (O\textsubscript{2}), they form calcium oxide (CaO):

• Formula: \(2\text{Ca(s)} + \text{O}_{2}(g) \rightarrow 2\text{CaO}(s)\)
• Calcium and oxygen combine in a 2:1 molar ratio.
• Products: Calcium oxide (CaO).

Combustion Reaction

Combustion reactions involve a substance reacting rapidly with oxygen, often producing heat and light.
These reactions are typical for organic compounds and are used in energy generation. Let's look at the combustion of benzene (C\textsubscript{6}H\textsubscript{6}):

• Formula: \(2\text{C}_{6}\text{H}_{6}(g) + 15\text{O}_{2}(g) \rightarrow 12\text{CO}_{2}(g) + 6\text{H}_{2}\text{O}(g)\)
• Benzene reacts with oxygen in a 2:15 molar ratio.
• Products: Carbon dioxide (CO\textsubscript{2}) and water (H\textsubscript{2}O).

Decomposition Reaction

Decomposition reactions involve a single substance breaking down into two or more products.
These reactions typically require energy input. Consider the decomposition of lead(IV) oxide (PbO\textsubscript{2}):

• Formula: \(2\text{PbO}_{2}(s) \rightarrow 2\text{PbO}(s) + \text{O}_{2}(g)\)
• Lead(IV) oxide decomposes into lead(II) oxide (PbO) and oxygen (O\textsubscript{2}).
• Energy is needed to initiate the breakdown.

Single Replacement Reaction

Single replacement reactions occur when an element replaces another element in a compound.
This type of reaction is common in metals and nonmetals. For instance, chlorine (Cl\textsubscript{2}) replaces iodine (I) in potassium iodide (KI):

• Formula: \(2\text{KI(s)} + \text{Cl}_{2}(g) \rightarrow 2\text{KCl}(s) + \text{I}_{2}(s)\)
• Chlorine replaces iodine in the compound.
• Products: Potassium chloride (KCl) and iodine (I\textsubscript{2}).

Double Replacement Reaction

Double replacement reactions involve the exchange of ions between two compounds.
Such reactions occur in aqueous solutions. Take the reaction between copper(II) chloride (CuCl\textsubscript{2}) and sodium sulfide (Na\textsubscript{2}S):

• Formula: \(\text{CuCl}_2(aq) + \text{Na}_2\text{S}(aq) \rightarrow \text{CuS}(s) + 2\text{NaCl}(aq)\)
• Ions are exchanged to form new compounds.
• Products: Copper(II) sulfide (CuS) and sodium chloride (NaCl).

Balancing Chemical Equations

Balancing chemical equations ensures mass conservation by ensuring equal numbers of each type of atom on both sides of the equation.
This is crucial because atoms cannot be created or destroyed in a chemical reaction.
To balance a chemical equation:

• Write the unbalanced equation.
• Count atoms for each element on both sides.
• Add coefficients to balance the atoms.
• Check to ensure all atoms are balanced and adjust if necessary.

For instance:

• Unbalanced: \(2\text{C}_{6}\text{H}_{6}(g) + \text{O}_{2}(g) \rightarrow \text{CO}_{2}(g) + \text{H}_{2}\text{O}(g)\)
• Balanced: \(2\text{C}_{6}\text{H}_{6}(g) + 15\text{O}_{2}(g) \rightarrow 12\text{CO}_{2}(g) + 6\text{H}_{2}\text{O}(g)\)