Question

Write and balance each of the following equations, and then identify each by type. a. hydrogen \(+\) iodine \(\longrightarrow\) hydrogen iodide b. lithium + hydrochloric acid \(\longrightarrow\) lithium chloride \(+\) hydrogen c. sodium carbonate \(\longrightarrow\) sodium oxide \(+\) carbon dioxide d. mercury (II) oxide \(\longrightarrow\) mercury \(+\) oxygen e. magnesium hydroxide \(\longrightarrow\) magnesium oxide + water

Short answer

a. H\(_2\) + I\(_2\) → 2HI (Synthesis)b. 2Li + 2HCl → 2LiCl + H\(_2\) (Single-displacement)c. Na\(_2\)CO\(_3\) → Na\(_2\)O + CO\(_2\) (Decomposition)d. 2HgO → 2Hg + O\(_2\) (Decomposition)e. Mg(OH)\(_2\) → MgO + H\(_2\)O (Decomposition)

Step-by-step solution

Write the Unbalanced Equations

Write down the chemical formulas for each reactant and product for all given reactions. a. H\(_2\) + I\(_2\) → HI b. Li + HCl → LiCl + H\(_2\) c. Na\(_2\)CO\(_3\) → Na\(_2\)O + CO\(_2\) d. HgO → Hg + O\(_2\) e. Mg(OH)\(_2\) → MgO + H\(_2\)O

Balance the Equations

Adjust coefficients to balance each equation. This ensures that the number of atoms for each element is the same on both sides of the equation. a. H\(_2\) + I\(_2\) → 2HI b. 2Li + 2HCl → 2LiCl + H\(_2\) c. Na\(_2\)CO\(_3\) → Na\(_2\)O + CO\(_2\) d. 2HgO → 2Hg + O\(_2\) e. Mg(OH)\(_2\) → MgO + H\(_2\)O

Identify the Type of Reaction

Classify each balanced equation by reaction type. a. Synthesis (H\(_2\) + I\(_2\) → 2HI) b. Single-displacement (2Li + 2HCl → 2LiCl + H\(_2\)) c. Decomposition (Na\(_2\)CO\(_3\) → Na\(_2\)O + CO\(_2\)) d. Decomposition (2HgO → 2Hg + O\(_2\)) e. Decomposition (Mg(OH)\(_2\) → MgO + H\(_2\)O)

Key concepts

balancing chemical equations

Balancing chemical equations is essential for understanding chemical reactions. In any chemical equation, the mass and the charge must be balanced on both sides of the reaction. This follows the Law of Conservation of Mass, which states that matter cannot be created or destroyed. To balance an equation, you have to adjust the coefficients (the numbers in front of the elements or compounds) to ensure the number of atoms of each element is the same on both sides.
For example: In the unbalanced equation: H\(_2\) + I\(_2\) → HI, we count the atoms on each side: 2 hydrogen atoms and 2 iodine atoms on the left and only 1 hydrogen and 1 iodine atom on the right. By placing a coefficient of 2 before HI, we balance the equation: H\(_2\) + I\(_2\) → 2HI.

reaction types

Chemical reactions can be classified into various types based on how reactants transform into products. The main reaction types are Synthesis, Decomposition, Single-displacement, and Double-displacement reactions. Understanding these types helps to predict the products of a reaction and understand chemical behavior.
For example, in the exercise, different reaction types include synthesis and decomposition.

synthesis reaction

A synthesis reaction occurs when two or more simple substances combine to form a more complex substance. It can be represented as: \( A + B \rightarrow AB \). These reactions usually release energy in the form of heat and light.
An example from the exercise is: H\(_2\) + I\(_2\) → 2HI, where hydrogen and iodine combine to form hydrogen iodide.

single-displacement reaction

In a single-displacement reaction, one element replaces another element in a compound. These reactions can be represented as: \( A + BC \rightarrow AC + B \). Metals and non-metals can displace each other depending on their reactivity.
In the exercise, an example of a single-displacement reaction is: 2Li + 2HCl → 2LiCl + H\(_2\), where lithium displaces hydrogen in hydrochloric acid to form lithium chloride and hydrogen gas.

decomposition reaction

A decomposition reaction occurs when a single compound breaks down into two or more simpler substances. It can be represented as: \( AB \rightarrow A + B \). These reactions often require an external source of energy, like heat, light, or electricity.
Several examples from the exercise include: Na\(_2\)CO\(_3\) → Na\(_2\)O + CO\(_2\) (decomposition of sodium carbonate), 2HgO → 2Hg + O\(_2\) (decomposition of mercury (II) oxide), and Mg(OH)\(_2\) → MgO + H\(_2\)O (decomposition of magnesium hydroxide).