Which Of The Following Chemical Equations Is Balanced

Which of the following chemicalequations is balanced?
Understanding how to determine whether a chemical equation obeys the law of conservation of mass is a fundamental skill in chemistry. This article walks you through the principles of balancing equations, provides a step‑by‑step checklist, highlights common pitfalls, and presents several practice problems so you can confidently identify the correctly balanced equation among a set of options.

Introduction

A chemical equation is a symbolic representation of a reaction, showing the reactants on the left and the products on the right. For the equation to be scientifically valid, the number of each type of atom must be identical on both sides. When this condition holds, we say the equation is balanced. The ability to spot a balanced equation quickly is essential for solving stoichiometry problems, predicting reaction yields, and interpreting laboratory data.

How to Check If a Chemical Equation Is Balanced ### 1. List the atoms present Write down every element that appears in the reactants and products. Include any polyatomic ions that remain unchanged during the reaction; treating them as single units can simplify the count.

2. Count atoms on each side

For each element (or polyatomic ion), tally the number of atoms contributed by every coefficient and subscript. Remember that a coefficient multiplies everything that follows it in the formula.

3. Compare the tallies

If the counts match for every element, the equation satisfies the conservation of mass and is balanced. Any mismatch indicates that the equation needs adjustment.

4. Adjust coefficients (if needed)

Start with the most complex molecule, change coefficients to equalize the counts, and repeat the verification. Never alter subscripts, as doing so changes the identity of the substance.

Step‑by‑Step Procedure (Checklist)

1. Identify all reactants and products.
2. Write the unordered list of elements.
3. Create a two‑column table: left side for reactants, right side for products.
4. Fill in the counts using coefficients and subscripts.
5. Check each row: if numbers are equal, move to the next element; if not, note the discrepancy.
6. Iteratively adjust coefficients beginning with the element that shows the largest imbalance.
7. Re‑check the entire table after each adjustment.
8. When all rows match, the equation is balanced.

Tip: Treat polyatomic ions such as (\text{SO}_4^{2-}) or (\text{NH}_4^{+}) as single units when they appear unchanged on both sides; this reduces bookkeeping errors.

Common Mistakes to Avoid

• Changing subscripts to fix an imbalance (e.g., turning ( \text{H}_2\text{O} ) into ( \text{H}_3\text{O} )). This alters the chemical identity.
• Ignoring diatomic elements like ( \text{O}_2 ), ( \text{N}_2 ), or ( \text{H}_2 ) when counting atoms.
• Overlooking coefficients that appear before parentheses, which multiply everything inside.
• Assuming that equal numbers of molecules mean the equation is balanced, without checking each element separately.
• Skipping the final verification after making adjustments, which can leave a hidden imbalance.

Scientific Explanation: Law of Conservation of Mass

The principle that matter cannot be created or destroyed in a chemical reaction underlies the need for balanced equations. Formulated by Antoine Lavoisier in the late 18th century, the law states that the total mass of reactants equals the total mass of products. When we count atoms, we are essentially ensuring that the mass contributed by each element is conserved. This concept also connects to modern ideas about atomic theory and stoichiometry, where balanced equations allow chemists to calculate exact quantities of substances needed or produced.

Practice Problems: Identify the Balanced Equation

Below are four sets of options. For each set, determine which chemical equation is balanced. Show your work using the checklist, then verify your answer.

Problem 1

A. ( \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3 )
B. ( 4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 )
C. ( 2\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 )
D. ( \text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 )

Solution:

• Count Fe: A (1 vs 2), B (4 vs 4), C (2 vs 4), D (1 vs 4).
• Count O: A (2 vs 3), B (6 vs 6), C (6 vs 6), D (6 vs 6).
  Only option B has equal Fe and O atoms.

Answer: B.

Problem 2

A. ( \text{C}_2\text{H}_6 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} )
B. ( 2\text{C}_2\text{H}_6 + 7\text{O}_2 \rightarrow 4\text{CO}_2 + 6\text{H}_2\text{O} ) C. ( \text{C}_2\text{H}_6 + \frac{7}{2}\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O} )
D. ( \text{C}_2\text{H}_6 + 5\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O} )

Solution:

• Option B: C (4 vs 4), H (12 vs 12), O (14 vs (8+6)=14). Balanced. - Option C uses a fractional coefficient; while mathematically correct, conventional balanced equations employ whole numbers. - Options A and D are unbalanced.

Answer: B (preferred whole‑number form).

Problem 3

A. ( \text{NaCl} + \text{AgNO}_3 \rightarrow \text{NaNO}_3 + \text{AgCl} )
B. ( 2\text{NaCl} + \text{AgNO}_3 \rightarrow 2\text{NaNO}_3 + \text{AgCl} )
C. ( \text{NaCl} + 2\text{AgNO}_3 \rightarrow \text{

Practice Problems: Identify the Balanced Equation

Below are four sets of options. For each set, determine which chemical equation is balanced. Show your work using the checklist, then verify your answer.

Problem 3

A. ( \text{NaCl} + \text{AgNO}_3 \rightarrow \text{AgCl} + \text{NaNO}_3 )
B. ( 2\text{NaCl} + \text{AgNO}_3 \rightarrow 2\text{AgCl} + \text{NaNO}_3 )
C. ( \text{NaCl} + 2\text{AgNO}_3 \rightarrow \text{AgCl} + \text{NaNO}_3 )
D. ( \text{NaCl} + \text{AgNO}_3 \rightarrow \text{AgCl} + 2\text{NaNO}_3 )

Solution:

• Option A: Na (1 vs 1), Cl (1 vs 1), Ag (1 vs 1), N (1 vs 1), O (3 vs 3). Balanced.
• Option B: Na (2 vs 1), Cl (2 vs 1), Ag (2 vs 1). Unbalanced.
• Option C: Na (1 vs 1), Cl (1 vs 1), Ag (2 vs 1). Unbalanced.
• Option D: Na (1 vs 2), Cl (1 vs 1), Ag (1 vs 1). Unbalanced.

Answer: A.

Problem 4

A. ( \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O} )
B. ( 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} )
C. ( \text{H}_2 + 2\text{O}_2 \rightarrow 2\text{H}_2\text{O} )
D. ( 2\text{H}_2 + 2\text{O}_2 \rightarrow 4\text{H}_2\text{O} )

Solution:

• Option A: H (2 vs 2), O (2 vs 1). Unbalanced.
• Option B: H (4 vs 4), O (2 vs 2). Balanced.
• Option C: H (2 vs 4), O (2 vs 2). Unbalanced.
• Option D: H (4 vs 8), O (2 vs 4). Unbalanced.

Answer: B.

Conclusion

Balancing chemical equations is not merely a mathematical exercise but a fundamental requirement for accurately representing chemical reactions. The Law of Conservation of Mass dictates that atoms are neither created nor destroyed, making balanced equations essential for predicting reaction outcomes, calculating stoichiometric ratios, and ensuring safety in laboratory settings. Common pitfalls, such as assuming balance by atom count alone or neglecting final verification, can lead to significant errors. By systematically applying the checklist—counting atoms for each element, adjusting coefficients proportionally, and cross-verifying—chemists uphold precision and reliability in their work. Mastery of this skill bridges theoretical principles with practical applications, reinforcing the interconnectedness of atomic theory, thermodynamics, and real-world chemical processes.

Conclusion (Continued)

Furthermore, the ability to balance equations extends beyond simple reactants and products. Complex reactions involving multiple steps and intermediates require careful analysis to ensure the conservation of mass at each stage. Understanding the nuances of balancing, including the use of parentheses and coefficients greater than one, is crucial for accurately depicting intricate chemical transformations.

In essence, balancing chemical equations is a cornerstone of chemical literacy. It facilitates communication within the scientific community, allowing for the unambiguous representation of chemical processes. From industrial chemistry and pharmaceutical development to environmental science and materials engineering, the ability to accurately balance and interpret chemical equations is indispensable. Therefore, consistent practice and a thorough understanding of the underlying principles are paramount to achieving proficiency in this essential skill, empowering scientists and students alike to unlock the secrets of the chemical world.