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Ch.9 - Thermochemistry: Chemical Energy
Chapter 9, Problem 103b

Write balanced equations for the formation of the following compounds from their elements. (b) Sodium sulfate

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Identify the elements present in sodium sulfate (Na2SO4). Sodium sulfate contains sodium (Na), sulfur (S), and oxygen (O).
Write the unbalanced equation using the elemental forms of each component. Sodium is typically found in its metallic form, sulfur in its solid form, and oxygen as a diatomic gas. The unbalanced equation is: \( \text{Na} + \text{S} + \text{O}_2 \rightarrow \text{Na}_2\text{SO}_4 \).
Balance the sodium atoms. Since there are two sodium atoms in sodium sulfate, you need two sodium atoms on the reactant side: \( 2\text{Na} + \text{S} + \text{O}_2 \rightarrow \text{Na}_2\text{SO}_4 \).
Balance the sulfur atoms. There is one sulfur atom in sodium sulfate and one sulfur atom in the elemental form, so the sulfur is already balanced.
Balance the oxygen atoms. There are four oxygen atoms in sodium sulfate. Since each molecule of oxygen gas (O2) contains two oxygen atoms, you need two molecules of oxygen gas: \( 2\text{Na} + \text{S} + 2\text{O}_2 \rightarrow \text{Na}_2\text{SO}_4 \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Equations

Chemical equations represent the reactants and products in a chemical reaction. They must be balanced to obey the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Each element's number of atoms must be the same on both sides of the equation, ensuring that the total mass remains constant.
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Formation Reactions

A formation reaction is a specific type of chemical reaction where elements combine to form a compound. In these reactions, the elements are in their standard states, and the reaction produces one mole of the compound. Understanding how to write formation reactions is essential for constructing balanced equations for compounds like sodium sulfate.
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Sodium Sulfate Composition

Sodium sulfate (Na2SO4) is composed of sodium (Na), sulfur (S), and oxygen (O). To write the balanced equation for its formation, one must recognize that it is formed from its constituent elements: sodium metal, sulfur, and oxygen gas. The correct stoichiometry must be applied to ensure that the number of each type of atom is conserved in the balanced equation.
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