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Ch.9 - Thermochemistry: Chemical Energy
Chapter 9, Problem 102b

Write balanced equations for the formation of the following compounds from their elements. (b) Sucrose (table sugar, C12H22O11)

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Identify the elements involved in forming sucrose, which are carbon (C), hydrogen (H), and oxygen (O).
Write the basic unbalanced equation using the molecular formula of sucrose: \( C + H_2 + O_2 \rightarrow C_{12}H_{22}O_{11} \).
Balance the carbon atoms first. Since there are 12 carbon atoms in sucrose, you need 12 carbon atoms on the reactant side: \( 12C + H_2 + O_2 \rightarrow C_{12}H_{22}O_{11} \).
Next, balance the hydrogen atoms. There are 22 hydrogen atoms in sucrose, so you need 11 molecules of hydrogen gas (since each molecule of hydrogen gas, H2, contains 2 hydrogen atoms): \( 12C + 11H_2 + O_2 \rightarrow C_{12}H_{22}O_{11} \).
Finally, balance the oxygen atoms. There are 11 oxygen atoms in sucrose, and since each molecule of oxygen gas (O2) contains 2 oxygen atoms, you need 11/2 molecules of oxygen gas. However, to keep the equation with whole numbers, multiply all coefficients by 2: \( 24C + 22H_2 + 11O_2 \rightarrow 2C_{12}H_{22}O_{11} \).

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Key Concepts

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

Balanced Chemical Equations

A balanced chemical equation represents a chemical reaction where the number of atoms for each element is the same on both sides of the equation. This is crucial for obeying the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Balancing equations involves adjusting coefficients to ensure that the total number of each type of atom is equal.
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Formation Reactions

A formation reaction is a specific type of chemical reaction where a compound is formed from its constituent elements in their standard states. For example, the formation of sucrose from carbon, hydrogen, and oxygen involves combining these elements in a specific ratio to create the compound. Understanding formation reactions is essential for writing accurate balanced equations for compound synthesis.
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Stoichiometry

Stoichiometry is the area of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to calculate the amounts of substances consumed and produced in a reaction based on balanced equations. Mastery of stoichiometry is vital for determining the correct coefficients needed to balance the formation of compounds like sucrose.
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