Free Balancing Chemical Equations Worksheet Answer Key - Free Printable

The task involves balancing chemical equations. Balancing a chemical equation ensures that the number of atoms of each element is the same on both sides of the equation (reactants and products). Below, I will explain the process for balancing chemical equations using one example from the list, and then provide the balanced equations for all the given reactions.

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General Steps to Balance Chemical Equations:

1. Write the Unbalanced Equation: Start with the given chemical equation.
2. Count the Atoms: Count the number of atoms of each element on both sides of the equation.
3. Balance Elements One by One:
- Start with elements that appear in only one compound on each side.
- Use coefficients (numbers placed in front of formulas) to balance the equation.
- Avoid changing subscripts within formulas, as this would alter the identity of the compounds.
4. Check Your Work: Ensure that the number of atoms of each element is the same on both sides.
5. Simplify Coefficients: If possible, reduce the coefficients to their simplest whole-number ratio.

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Example Explanation:

Let's balance the equation for reaction 5:
\[ \text{Pb(OH)}_2 + \text{HCl} \rightarrow \text{H}_2\text{O} + \text{PbCl}_2 \]

#### Step 1: Write the unbalanced equation.
\[ \text{Pb(OH)}_2 + \text{HCl} \rightarrow \text{H}_2\text{O} + \text{PbCl}_2 \]

#### Step 2: Count the atoms.
- Reactants:
- Pb: 1
- O: 2
- H: 2
- Cl: 1
- Products:
- Pb: 1
- O: 1
- H: 2
- Cl: 2

#### Step 3: Balance the equation.
- Balance Cl: There is 1 Cl atom in HCl on the left and 2 Cl atoms in PbCl₂ on the right. Add a coefficient of 2 to HCl.
\[ \text{Pb(OH)}_2 + 2\text{HCl} \rightarrow \text{H}_2\text{O} + \text{PbCl}_2 \]
- Balance O: There are 2 O atoms in Pb(OH)₂ on the left and 1 O atom in H₂O on the right. Add a coefficient of 2 to H₂O.
\[ \text{Pb(OH)}_2 + 2\text{HCl} \rightarrow 2\text{H}_2\text{O} + \text{PbCl}_2 \]
- Balance H: There are 4 H atoms in 2 HCl and 2 H atoms in Pb(OH)₂ on the left, totaling 6 H atoms. On the right, there are 4 H atoms in 2 H₂O. This is balanced.
- Check Pb: There is 1 Pb atom on both sides.
- Check Cl: There are 2 Cl atoms on both sides.

#### Step 4: Verify the balanced equation.
\[ \text{Pb(OH)}_2 + 2\text{HCl} \rightarrow 2\text{H}_2\text{O} + \text{PbCl}_2 \]

All atoms are balanced.

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Balanced Equations for All Reactions:

1. \( \text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3 \)
2. \( 2\text{KClO}_3 \rightarrow 2\text{KCl} + 3\text{O}_2 \)
3. \( 2\text{NaCl} + \text{F}_2 \rightarrow 2\text{NaF} + \text{Cl}_2 \)
4. \( 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} \)
5. \( \text{Pb(OH)}_2 + 2\text{HCl} \rightarrow 2\text{H}_2\text{O} + \text{PbCl}_2 \)
6. \( 2\text{AlBr}_3 + 3\text{K}_2\text{SO}_4 \rightarrow 6\text{KBr} + \text{Al}_2(\text{SO}_4)_3 \)
7. \( \text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} \)
8. \( \text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O} \)
9. \( 2\text{C}_8\text{H}_{18} + 25\text{O}_2 \rightarrow 16\text{CO}_2 + 18\text{H}_2\text{O} \)
10. \( \text{FeCl}_3 + 3\text{NaOH} \rightarrow \text{Fe(OH)}_3 + 3\text{NaCl} \)
11. \( 4\text{P} + 5\text{O}_2 \rightarrow 2\text{P}_2\text{O}_5 \)
12. \( 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \)
13. \( 2\text{Ag}_2\text{O} \rightarrow 4\text{Ag} + \text{O}_2 \)
14. \( \text{S}_8 + 12\text{O}_2 \rightarrow 8\text{SO}_3 \)
15. \( 6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \)
16. \( \text{K} + \text{MgBr}_2 \rightarrow \text{KBr} + \text{Mg} \)
17. \( 2\text{HCl} + \text{CaCO}_3 \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \)
18. \( \text{HNO}_3 + \text{NaHCO}_3 \rightarrow \text{NaNO}_3 + \text{H}_2\text{O} + \text{CO}_2 \)
19. \( 2\text{H}_2\text{O} + \text{O}_2 \rightarrow 2\text{H}_2\text{O}_2 \)
20. \( 2\text{NaBr} + \text{CaF}_2 \rightarrow 2\text{NaF} + \text{CaBr}_2 \)
21. \( \text{H}_2\text{SO}_4 + 2\text{NaNO}_2 \rightarrow 2\text{HNO}_2 + \text{Na}_2\text{SO}_4 \)

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Final Answer:

\[
\boxed{
\begin{aligned}
1. & \quad \text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3 \\
2. & \quad 2\text{KClO}_3 \rightarrow 2\text{KCl} + 3\text{O}_2 \\
3. & \quad 2\text{NaCl} + \text{F}_2 \rightarrow 2\text{NaF} + \text{Cl}_2 \\
4. & \quad 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} \\
5. & \quad \text{Pb(OH)}_2 + 2\text{HCl} \rightarrow 2\text{H}_2\text{O} + \text{PbCl}_2 \\
6. & \quad 2\text{AlBr}_3 + 3\text{K}_2\text{SO}_4 \rightarrow 6\text{KBr} + \text{Al}_2(\text{SO}_4)_3 \\
7. & \quad \text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} \\
8. & \quad \text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O} \\
9. & \quad 2\text{C}_8\text{H}_{18} + 25\text{O}_2 \rightarrow 16\text{CO}_2 + 18\text{H}_2\text{O} \\
10. & \quad \text{FeCl}_3 + 3\text{NaOH} \rightarrow \text{Fe(OH)}_3 + 3\text{NaCl} \\
11. & \quad 4\text{P} + 5\text{O}_2 \rightarrow 2\text{P}_2\text{O}_5 \\
12. & \quad 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \\
13. & \quad 2\text{Ag}_2\text{O} \rightarrow 4\text{Ag} + \text{O}_2 \\
14. & \quad \text{S}_8 + 12\text{O}_2 \rightarrow 8\text{SO}_3 \\
15. & \quad 6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \\
16. & \quad \text{K} + \text{MgBr}_2 \rightarrow \text{KBr} + \text{Mg} \\
17. & \quad 2\text{HCl} + \text{CaCO}_3 \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \\
18. & \quad \text{HNO}_3 + \text{NaHCO}_3 \rightarrow \text{NaNO}_3 + \text{H}_2\text{O} + \text{CO}_2 \\
19. & \quad 2\text{H}_2\text{O} + \text{O}_2 \rightarrow 2\text{H}_2\text{O}_2 \\
20. & \quad 2\text{NaBr} + \text{CaF}_2 \rightarrow 2\text{NaF} + \text{CaBr}_2 \\
21. & \quad \text{H}_2\text{SO}_4 + 2\text{NaNO}_2 \rightarrow 2\text{HNO}_2 + \text{Na}_2\text{SO}_4 \\
\end{aligned}
}
\]