Problem 18 - Chemistry and Chemical Reactivity

Question

Complete and balance the equations for the following reactions: (a) \(\mathrm{K}(\mathrm{s})+\mathrm{I}_{2}(\mathrm{g}) \rightarrow\) (c) \(\mathrm{Al}(\mathrm{s})+\mathrm{S}_{8}(\mathrm{s}) \rightarrow\) (b) \(\mathrm{Ba}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow\) (d) \(\mathrm{Si}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g}) \rightarrow\)

Step-by-Step Solution

Answer

Balanced equations: (a) \(2\mathrm{K} + \mathrm{I}_2 \rightarrow 2\mathrm{KI}\), (b) \(2\mathrm{Ba} + \mathrm{O}_2 \rightarrow 2\mathrm{BaO}\), (c) \(16\mathrm{Al} + 3\mathrm{S}_8 \rightarrow 8\mathrm{Al}_2\mathrm{S}_3\), (d) \(\mathrm{Si} + 2\mathrm{Cl}_2 \rightarrow \mathrm{SiCl}_4\).

Step 1: Identify Reaction Types

Examine each reaction to determine the type of reaction: synthesis, decomposition, single replacement, or double replacement. In this case, all the reactions provided are synthesis reactions, where two or more reactants combine to form a single product.

Step 2: Write Products

For each reaction, write the product based on knowledge of chemical compounds formed:(a) Potassium iodine: \(\mathrm{K} + \mathrm{I}_2 \rightarrow \mathrm{KI}\)(b) Barium oxide: \(\mathrm{Ba} + \mathrm{O}_2 \rightarrow \mathrm{BaO}\)(c) Aluminum sulfide: \(\mathrm{Al} + \mathrm{S}_8 \rightarrow \mathrm{Al}_2\mathrm{S}_3\)(d) Silicon chloride: \(\mathrm{Si} + \mathrm{Cl}_2 \rightarrow \mathrm{SiCl}_4\)

Step 3: Balance Equation for Potassium Iodide

Balance \(\mathrm{K} + \mathrm{I}_2 \rightarrow \mathrm{KI}\):- Balance iodine: 1 mole of \(\mathrm{I}_2\) requires 2 moles of \(\mathrm{KI}\).- Adding 2 moles of \(\mathrm{K}\) on the left to balance potassium results in the balanced equation: \(2\mathrm{K}(\mathrm{s}) + \mathrm{I}_2(\mathrm{g}) \rightarrow 2\mathrm{KI}(\mathrm{s})\).

Step 4: Balance Equation for Barium Oxide

Balance \(\mathrm{Ba} + \mathrm{O}_2 \rightarrow \mathrm{BaO}\):- Balance oxygen: 1 mole of \(\mathrm{O}_2\) produces 2 moles of \(\mathrm{BaO}\).- Balance barium: 2 moles of \(\mathrm{Ba}\) are required to match the 2 moles of \(\mathrm{BaO}\), providing \(2\mathrm{Ba}(\mathrm{s}) + \mathrm{O}_2(\mathrm{g}) \rightarrow 2\mathrm{BaO}(\mathrm{s})\).

Step 5: Balance Equation for Aluminum Sulfide

Balance \(\mathrm{Al} + \mathrm{S}_8 \rightarrow \mathrm{Al}_2\mathrm{S}_3\):- Balance aluminum using 4 moles: \( 4\mathrm{Al}\).- Balance sulfur with 3/8 moles of \(\mathrm{S}_8\): This means balancing with integer moles, utilizing 8 moles of \(\mathrm{Al}_2\mathrm{S}_3\).- Balanced equation is \(16\mathrm{Al}(\mathrm{s}) + 3\mathrm{S}_8(\mathrm{s}) \rightarrow 8\mathrm{Al}_2\mathrm{S}_3(\mathrm{s})\).

Step 6: Balance Equation for Silicon Chloride

Balance \(\mathrm{Si} + \mathrm{Cl}_2 \rightarrow \mathrm{SiCl}_4\):- Balance chlorine: 2 moles of \(\mathrm{Cl}_2\) will balance the 4 chlorine atoms in \(\mathrm{SiCl}_4\).- Thus, the equation becomes \(\mathrm{Si}(\mathrm{s}) + 2\mathrm{Cl}_2(\mathrm{g}) \rightarrow \mathrm{SiCl}_4(\mathrm{l})\).

Key Concepts

Synthesis Reactions

In chemistry, synthesis reactions are a fundamental type of chemical reaction where two or more simple substances combine to form a more complex product. These reactions are sometimes called combination reactions. For example, consider the reaction between potassium and iodine to form potassium iodide. Here,

• Potassium (K) and iodine (\(\text{I}_2\)) react together.
• The result is the formation of potassium iodide (KI).

Synthesis reactions have a general formula: \( A + B \rightarrow AB \). Here, A and B are the reactants, and AB is the product formed from combining those reactants. These reactions are vital in creating chemical compounds we use in everyday life, from table salt to water.

Balancing Equations

Balancing chemical equations is an essential skill in chemistry that ensures the law of conservation of mass is upheld, stating that mass cannot be created or destroyed in a chemical reaction. This means the number of each type of atom must be the same on both the reactant and product sides of the equation.

• For instance, if you start with 2 moles of potassium in your reactants, you should end up with the same number of moles in your products.
• Furthermore, each individual type of atom: oxygen, sulfur, aluminum, etc., must also be balanced.

Balancing often involves adjusting coefficients, which are the numbers placed before compounds, to equalize the number of atoms on both sides. For instance, to balance the reaction of aluminum with sulfur, \( 16\text{Al} + 3\text{S}_8 \rightarrow 8\text{Al}_2\text{S}_3 \), you must ensure both aluminum and sulfur have the same number of atoms on both sides by multiplying their respective coefficients.

Chemical Compounds

Chemical compounds are substances formed when two or more elements are chemically bonded together. There are different types of chemical bonds such as ionic, covalent, and metallic bonds. The type of bond formed depends on the elements involved.

• In our examples: potassium iodide (KI) is an ionic compound.
• Barium oxide, aluminum sulfide, and silicon chloride also form as result of different bonding types appropriate to their elements.

A compound's properties, such as melting point, boiling point, reactivity, and more, are determined by the type and arrangement of its atoms. Understanding the composition is crucial in noticing how the substance will behave in various conditions.

Reaction Types

Chemical reactions can be categorized into several types, including synthesis, decomposition, single replacement, and double replacement.

• Synthesis reactions, as discussed earlier, involve combining elements or simpler compounds into more complex ones.
• Decomposition reactions do the opposite by breaking down compounds into simpler substances.
• Single replacement involves one element replacing another in a compound, while double replacement involves an exchange between two compounds.

Recognizing different reaction types helps in predicting products and understanding the chemical behavior of substances. All reactions in the given exercise are synthesis reactions, showcasing how reactants unite to form a single, more complex chemical compound.