Which of the Following Is a Correctly Balanced Equation?
Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is obeyed. And when atoms are conserved, the number of atoms of each element on the reactant side must equal the number on the product side. This article walks through the logic behind balancing equations, demonstrates common pitfalls, and provides a step‑by‑step analysis of several sample reactions to determine which one is correctly balanced.
Introduction
In chemistry, an equation is more than a symbolic representation; it is a statement of a chemical transformation that must satisfy a strict rule: mass conservation. An unbalanced equation can lead to erroneous predictions about stoichiometry, energy changes, and product yields. Which means, chemists routinely check that every equation is balanced before using it in calculations or experimental design.
The question “Which of the following is a correctly balanced equation?Consider this: ” is a typical problem found in textbooks and exams. Worth adding: it tests not only memorization of reaction types but also the ability to apply algebraic reasoning to count atoms. Below, we break down the balancing process, illustrate it with concrete examples, and explain how to spot the correct answer among a set of alternatives.
The Balancing Process Explained
1. Write the Skeleton Equation
The skeleton equation lists the reactants and products without coefficients:
[ \text{A} + \text{B} \rightarrow \text{C} + \text{D} ]
2. Count Atoms of Each Element
Create a table that tallies the number of atoms for every element on both sides. Take this case: in the reaction between nitrogen and hydrogen to form ammonia:
[ \text{N}_2 + \text{H}_2 \rightarrow \text{NH}_3 ]
The counts are:
| Element | Reactants | Products |
|---|---|---|
| N | 2 | 1 |
| H | 2 | 3 |
3. Assign Coefficients
Introduce variables (e.Worth adding: g. , (a, b, c, d)) as coefficients in front of each compound That's the part that actually makes a difference..
[ \begin{cases} 2a = c \ 2b = 3c \end{cases} ]
Solve for the smallest whole‑number coefficients that satisfy all equations.
4. Verify the Balance
After assigning coefficients, recalculate the atom counts to confirm equality on both sides. If any element is unbalanced, adjust coefficients and repeat Which is the point..
Common Mistakes to Avoid
| Mistake | Why It Happens | How to Fix It |
|---|---|---|
| Using fractions | Some students stop at fractional coefficients. | Multiply all coefficients by the least common denominator to obtain whole numbers. |
| Assuming the first solution is correct | Multiple sets of coefficients can satisfy the equations. | |
| Ignoring stoichiometric constraints | For reactions involving polyatomic ions, the overall charge may be overlooked. | Systematically check every element, even those that appear balanced at first glance. Practically speaking, |
| Neglecting to balance all elements | Focus may drift to the most obvious imbalance. | Verify charge balance in addition to atom counts. |
Sample Reactions and Analysis
Below are four reactions commonly presented in coursework. We will determine which one is correctly balanced.
-
Reaction A
[ \text{C}_2\text{H}_6 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} ] -
Reaction B
[ 2\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 ] -
Reaction C
[ \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O} ] -
Reaction D
[ 4\text{H}_2\text{O} \rightarrow 2\text{H}_2 + 2\text{O}_2 ]
Let’s examine each one.
Reaction A: Ethane Combustion
Skeleton:
[
\text{C}_2\text{H}_6 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}
]
Atom Counts (before coefficients):
| Element | Reactants | Products |
|---|---|---|
| C | 2 | 1 |
| H | 6 | 2 |
| O | 2 | 3 |
Assign Coefficients:
Let (a) be the coefficient for (\text{C}_2\text{H}_6), (b) for (\text{O}_2), (c) for (\text{CO}_2), (d) for (\text{H}_2\text{O}) Worth keeping that in mind..
Equations: [ \begin{aligned} 2a &= c \ 6a &= 2d \ 2b &= 3c + d \end{aligned} ]
Choosing (a = 1) gives (c = 2) and (d = 3). Plugging into the oxygen equation: [ 2b = 3(2) + 3 = 9 \Rightarrow b = 4.5 ] Since coefficients must be whole numbers, multiply all by 2: [ 2\text{C}_2\text{H}_6 + 9\text{O}_2 \rightarrow 4\text{CO}_2 + 6\text{H}_2\text{O} ]
Some disagree here. Fair enough.
Conclusion:
Reaction A as written is not balanced. The correct balanced form requires coefficients 2, 9, 4, and 6.
Reaction B: Iron Oxidation
Skeleton:
[
2\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3
]
Check Atom Counts:
| Element | Reactants | Products |
|---|---|---|
| Fe | (2 \times 1 = 2) | (2 \times 2 = 4) |
| O | (3 \times 2 = 6) | (2 \times 3 = 6) |
Fe is unbalanced: 2 vs. 4. To balance Fe, change the coefficient of Fe on the reactant side to 4:
[ 4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3 ]
Now Fe: 4 = 4, O: 6 = 6. Reaction B, as given, is not balanced.
Reaction C: Neutralization
Skeleton:
[
\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}
]
Atom Counts:
| Element | Reactants | Products |
|---|---|---|
| Na | 1 | 1 |
| O | 1 | 1 |
| H | 1 + 1 = 2 | 2 |
| Cl | 1 | 1 |
All elements are balanced. On top of that, coefficients are all 1. Reaction C is correctly balanced.
Reaction D: Electrolysis of Water
Skeleton:
[
4\text{H}_2\text{O} \rightarrow 2\text{H}_2 + 2\text{O}_2
]
Atom Counts:
| Element | Reactants | Products |
|---|---|---|
| H | (4 \times 2 = 8) | (2 \times 2 = 4) + (0 = 4) |
| O | (4 \times 1 = 4) | (2 \times 2 = 4) |
Hydrogen is unbalanced (8 vs. 4). To correct, double the coefficient of (\text{H}_2):
[ 4\text{H}_2\text{O} \rightarrow 4\text{H}_2 + 2\text{O}_2 ]
Now H: 8 = 8, O: 4 = 4. Reaction D, as written, is not balanced.
Which Equation Is Correctly Balanced?
From the analysis above, Reaction C (the neutralization of sodium hydroxide with hydrochloric acid) is the only one that is already balanced with integer coefficients. The other reactions require adjustment of coefficients to satisfy mass conservation.
Frequently Asked Questions
1. Why do some balanced equations use fractional coefficients?
Fractional coefficients can arise when the simplest set of integers is not immediately apparent. Multiplying all coefficients by the denominator of the fractions yields an equivalent balanced equation with whole numbers, which is the preferred form.
2. Do I need to balance charges in redox reactions?
Yes. That said, in redox reactions, balancing electrons (or charges) is essential. While the atom count ensures mass conservation, charge balance ensures electrical neutrality, especially in aqueous solutions.
3. Can a balanced equation be wrong if the reaction doesn't actually occur?
A mathematically balanced equation may represent a possible reaction, but it might be kinetically unfavorable or thermodynamically impossible. Chemistry balances constraints of both mass and energy.
4. How do I handle polyatomic ions that stay together?
Treat the polyatomic ion as a single unit when counting atoms. Here's one way to look at it: in (\text{CaSO}_4), count one calcium, one sulfur, and four oxygens as one compound Easy to understand, harder to ignore. That alone is useful..
5. Is there software that can balance equations automatically?
Yes, many computational tools and calculators can balance equations. On the flip side, understanding the underlying principles is crucial for interpreting results and troubleshooting errors Nothing fancy..
Conclusion
Balancing chemical equations is a disciplined exercise that reinforces the conservation of mass principle. Worth adding: by systematically counting atoms, assigning coefficients, and verifying balance, chemists can confidently write equations that reflect real chemical processes. Here's the thing — among the sample reactions examined, Reaction C stands out as the correctly balanced equation. Mastery of this skill not only prepares students for academic assessments but also equips them with a foundational tool for research, industry, and everyday problem-solving in chemistry And it works..
