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Ch.3 - Mass Relationships in Chemical Reactions
Chapter 3, Problem 42a

Balance the following equations. (a) C6H5NO2 + O2 --> CO2 + H2O + NO2

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Identify the number of each type of atom in the reactants and products. For C_6H_5NO_2, there are 6 carbon (C), 5 hydrogen (H), 1 nitrogen (N), and 2 oxygen (O) atoms. For O_2, there are 2 oxygen atoms. In the products, CO_2 has 1 carbon and 2 oxygen atoms, H_2O has 2 hydrogen and 1 oxygen atom, and NO_2 has 1 nitrogen and 2 oxygen atoms.
Start by balancing the carbon atoms. Since there are 6 carbon atoms in C_6H_5NO_2, you will need 6 CO_2 molecules to balance the carbon atoms on both sides of the equation.
Next, balance the hydrogen atoms. There are 5 hydrogen atoms in C_6H_5NO_2, so you will need 5/2 or 2.5 H_2O molecules to balance the hydrogen atoms. However, since we cannot have a fraction of a molecule, multiply all coefficients by 2 to eliminate the fraction.
Now, balance the nitrogen atoms. There is 1 nitrogen atom in C_6H_5NO_2, so you will need 1 NO_2 molecule to balance the nitrogen atoms.
Finally, balance the oxygen atoms. Count the total number of oxygen atoms needed on the product side and adjust the coefficient of O_2 in the reactants to ensure the total number of oxygen atoms is the same on both sides of the equation.

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Key Concepts

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

Balancing Chemical Equations

Balancing chemical equations involves ensuring that the number of atoms for each element is the same on both sides of the equation. This is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Coefficients are used to adjust the quantities of reactants and products to achieve balance.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It allows chemists to predict the amounts of substances consumed and produced in a reaction based on the balanced equation. Understanding stoichiometry is essential for determining how much of each reactant is needed and how much product can be formed.
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Types of Reactions

Chemical reactions can be classified into different types, such as combustion, synthesis, decomposition, and redox reactions. The given equation represents a combustion reaction, where a hydrocarbon reacts with oxygen to produce carbon dioxide and water. Recognizing the type of reaction helps in predicting the products and understanding the reaction mechanism.
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