A chemical reaction is represented by the following unbalanced chemical equation:
[tex]$Na _2( aq )+ HCl ( aq ) \rightarrow NaCl ( aq )+ H _2 S( g )$[/tex]
Which statement best describes why it is necessary to balance all chemical equations?
A. Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction.
B. Chemical reactions make new substances, so the new elements must be accounted for.
C. The total number of atoms in a chemical reaction are relative, so you can add as many as you want.
D. The total number of atoms in a chemical reaction can change as the reaction proceeds, so they must be identified first.
Answer (2)
Chemical equations must be balanced to adhere to the law of conservation of mass.
The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction.
Balancing ensures the number of atoms of each element is the same on both sides of the equation.
Therefore, the best statement is: Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction. $\boxed{Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction.}
Explanation
Understanding the Problem Let's analyze the question. We are given an unbalanced chemical equation and asked to choose the statement that best describes why chemical equations must be balanced. The key principle here is the law of conservation of mass.
Applying the Law of Conservation of Mass The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. This means the number of atoms of each element must be the same on both sides of the equation.
Evaluating the Statements Now let's evaluate the given statements:
Statement 1: "Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction." This statement accurately reflects the law of conservation of mass.
Statement 2: "Chemical reactions make new substances, so the new elements must be accounted for." While true that new substances are formed, this doesn't explain why we balance equations. Balancing is about conserving atoms, not just accounting for new elements.
Statement 3: "The total number of atoms in a chemical reaction are relative, so you can add as many as you want." This is incorrect. The number of atoms is not relative; it must be conserved.
Statement 4: "The total number of atoms in a chemical reaction can change as the reaction proceeds, so they must be identified first." This is also incorrect. The number of atoms does not change during a reaction.
Conclusion Based on the above analysis, the best statement is the one that directly reflects the law of conservation of mass.
Examples
Balancing chemical equations is like ensuring you have the same number of building blocks before and after constructing a Lego castle. If you start with 100 Lego bricks, you must end up with 100 bricks in your castle, even though they are arranged differently. Similarly, in a chemical reaction, the number of atoms of each element must remain the same, ensuring that matter is neither created nor destroyed, just rearranged. This principle is crucial in various fields, such as calculating the amount of reactants needed for a specific product or understanding the stoichiometry of a reaction.
The necessity to balance chemical equations stems from the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Thus, the best explanation is: 'Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction.' This principle ensures the correct representation of reactants and products in any chemical reaction.
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