Free Balancing Chemical Equations Worksheet Answer Key - Free Printable

It looks like you've uploaded an answer key for a worksheet titled *"Balancing Chemical Equations – Answer Key"*. This document provides the balanced chemical equations for 21 different reactions. Since this is already a completed answer key, it appears that the task was to balance chemical equations, and the solutions are provided.

However, if your goal is to understand how to balance these equations or verify the correctness of the answers, I can walk you through the process for a few examples and explain the general method.

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🔍 How to Balance Chemical Equations

Balancing chemical equations involves ensuring that the number of atoms of each element is equal on both sides (reactants and products), following the Law of Conservation of Mass.

Steps:
1. Write the unbalanced equation.
2. Count atoms of each element on both sides.
3. Use coefficients (whole numbers in front of formulas) to balance atoms.
4. Start with elements that appear in only one compound on each side.
5. Save hydrogen and oxygen for last (they often appear in multiple compounds).
6. Check all atoms again.

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✔ Let's verify a few from the list:

#### Example 1:
N₂ + H₂ → NH₃

- Left: N = 2, H = 2
- Right: N = 1, H = 3 → not balanced.

To balance:
- Put 2 NH₃ → now N = 2, H = 6 on right.
- Need 3 H₂ on left → gives H = 6.
- Final: N₂ + 3H₂ → 2NH₃ ✔

Matches the answer key.

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#### Example 8:
C₃H₈ + O₂ → CO₂ + H₂O

Unbalanced:
- C: 3 → need 3 CO₂
- H: 8 → need 4 H₂O (since each has 2 H)
- Now O: on right: 3×2 + 4×1 = 6 + 4 = 10 O → so need 5 O₂

So:
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O ✔
Matches answer key.

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#### Example 9:
C₈H₁₈ + O₂ → CO₂ + H₂O

- C: 8 → 8 CO₂
- H: 18 → 9 H₂O
- O: right = 8×2 + 9×1 = 16 + 9 = 25 → so need 25/2 O₂ → but must be whole number

Multiply entire equation by 2:
- 2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O ✔

Matches the key.

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#### Example 15:
CO₂ + H₂O → C₆H₁₂O₆ + O₂

This is photosynthesis.
- Left: C=1, H=2, O=3
- Right: C=6, H=12, O=6+2=8 → clearly unbalanced

We need 6 CO₂ and 6 H₂O → gives:
- C: 6, H: 12, O: 6×2 + 6×1 = 12 + 6 = 18
- Right: C₆H₁₂O₆ has 6C, 12H, 6O; O₂ has 2O → total O = 8 → too little

Wait — actually, correct balanced form is:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Check:
- Left: C=6, H=12, O=12 + 6 = 18
- Right: C=6, H=12, O=6 (in sugar) + 12 (in 6O₂) = 18 ✔

But the answer key says:
6 CO₂ + 6 H₂O → 1 C₆H₁₂O₆ + 6 O₂ → which is correct! ✔

Note: The original image shows “+ 6 O₂” — yes, it's correct.

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❗ Important Note:

The answer key appears mostly correct, but let’s check #16:

> 1 K + 1 MgBr → 1 KBr + 1 Mg

Wait — MgBr is not a real compound. Magnesium bromide is MgBr₂, since Mg²⁺ and Br⁻.

So the correct reaction should be:
2K + MgBr₂ → 2KBr + Mg

But the key says:
1 K + 1 MgBr → 1 KBr + 1 Mg

This is incorrect due to incorrect formula.

✔ Corrected version:
2K + MgBr₂ → 2KBr + Mg

So #16 is wrong in the key.

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Summary of Corrections:

| Problem | Original Answer | Correction |
|-------|------------------|-----------|
| 16 | K + MgBr → KBr + Mg | Incorrect: MgBr should be MgBr₂ → use 2K + MgBr₂ → 2KBr + Mg |

All others seem correct.

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✔ Final Thoughts:

- The answer key is mostly accurate.
- One major error: #16 uses an invalid formula (MgBr instead of MgBr₂).
- If this were a student worksheet, they should be taught that magnesium forms Mg²⁺, so magnesium bromide is MgBr₂, not MgBr.

Let me know if you'd like:
- A full walkthrough of any specific equation,
- A printable version of corrected answers,
- Or help creating similar problems.

Would you like that?