Problem 14 - Chemistry and Chemical Reactivity

Question

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

Step-by-Step Solution

Answer

(a) \( 2K + I_2 \rightarrow 2KI \) (b) \( 2Ba + O_2 \rightarrow 2BaO \) (c) \( 16Al + 3S_8 \rightarrow 8Al_2S_3 \) (d) \( Si + 2Cl_2 \rightarrow SiCl_4 \)

Step 1: Identify Reaction Type

Determine what type of chemical reaction each equation represents. In all the given reactions, substances are combining, which indicates that these are synthesis reactions, where two or more reactants combine to form a single product.

Step 2: Predict the Products

Based on the reactants provided:(a) Potassium (K) reacts with iodine (\( I_2 \) ) to form potassium iodide (\( KI \) ).(b) Barium (Ba) reacts with oxygen (\( O_2 \) ) to form barium oxide (\( BaO \) ).(c) Aluminum (Al) reacts with sulfur (\( S_8 \) ) to form aluminum sulfide (\( Al_2S_3 \) ).(d) Silicon (Si) reacts with chlorine (\( Cl_2 \) ) to form silicon tetrachloride (\( SiCl_4 \) ).

Step 3: Balance Chemical Equations

Adjust the coefficients to ensure that the number of atoms for each element is balanced on both sides of the equation.(a) \[ 2K + I_2 ightarrow 2KI \](b) \[ 2Ba + O_2 ightarrow 2BaO \](c) \[ 16Al + 3S_8 ightarrow 8Al_2S_3 \](d) \[ Si + 2Cl_2 ightarrow SiCl_4 \]

Step 4: Verify Balanced Equations

Check each balanced equation to ensure that the count of each type of atom on the left side (reactants) is equal to the count on the right side (products). (a) 2 K and 2 I on both sides. (b) 2 Ba and 2 O on both sides. (c) 16 Al and 24 S on both sides. (d) 1 Si and 4 Cl on both sides.

Key Concepts

Synthesis Reactions

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 crucial in many industrial and biological processes. A synthesis reaction typically follows the pattern \( A + B \rightarrow AB \), where different elements or simpler compounds merge into a single compound. For example, when potassium \( K \) reacts with iodine \( I_2 \), they form potassium iodide \( KI \), which is a classic synthesis reaction. Understanding these reactions helps us predict how different elements can combine to form new substances.

Predicting Products

Predicting the products of a reaction involves understanding the chemical properties of the reactants. By knowing the types of atoms involved, we can forecast the products a reaction might produce. For instance:

• Potassium and iodine will form potassium iodide \( KI \).
• Barium and oxygen combine to make barium oxide \( BaO \).
• Aluminum and sulfur yield aluminum sulfide \( Al_2S_3 \).
• Silicon reacting with chlorine results in silicon tetrachloride \( SiCl_4 \).

These predictions are made by combining the known valences and typical compounds these elements form. This approach helps chemists deduce the outcomes of chemical reactions before they occur.

Chemical Reaction Types

Chemical reactions are categorized into several types based on the process and the products formed. Synthesis, decomposition, single replacement, double replacement, and combustion are some of the main types. Specifically, in synthesis reactions, the key is that multiple reactants form a single product. For example, in the reaction of aluminum with sulfur, we start with these distinct elements and end up with aluminum sulfide, a compound that incorporates both elements. Knowing the reaction type helps in understanding the underlying chemical processes and anticipating the outcomes.

Stoichiometry

Stoichiometry refers to the part of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It involves using balanced chemical equations to calculate amounts of substances. For example, in the balanced equation \( 16Al + 3S_8 \rightarrow 8Al_2S_3 \), stoichiometry helps us understand that 16 moles of aluminum react with 3 moles of sulfur to produce 8 moles of aluminum sulfide. By balancing the equation, we ensure the law of conservation of mass is observed, meaning matter is neither created nor destroyed. This makes stoichiometry crucial for precise calculations in chemical reactions and processes.