Practice sheet for balancing chemical equations with various reactions involving elements and compounds.

To balance the given chemical equations, we need to ensure that the number of atoms of each element is the same on both sides of the equation. Here are the balanced equations along with explanations:

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1. Fe + O₂ → Fe₃O₄

- Initial Equation: Fe + O₂ → Fe₃O₄
- Analysis:
- On the left: 1 Fe, 2 O
- On the right: 3 Fe, 4 O
- Balancing:
- To balance Fe, multiply Fe by 3.
- To balance O, multiply O₂ by 2 (since 2 × 2 = 4).
- Balanced Equation: 3Fe + 2O₂ → Fe₃O₄

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2. Sr + O₂ → SrO

- Initial Equation: Sr + O₂ → SrO
- Analysis:
- On the left: 1 Sr, 2 O
- On the right: 1 Sr, 1 O
- Balancing:
- To balance O, multiply SrO by 2.
- Balanced Equation: 2Sr + O₂ → 2SrO

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3. Sn + NaOH → Na₂SnO₂ + H₂

- Initial Equation: Sn + NaOH → Na₂SnO₂ + H₂
- Analysis:
- On the left: 1 Sn, 1 Na, 1 O, 1 H
- On the right: 1 Sn, 2 Na, 2 O, 2 H
- Balancing:
- To balance Na and H, multiply NaOH by 2.
- Balanced Equation: Sn + 2NaOH → Na₂SnO₂ + H₂

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4. K + Br₂ → KBr

- Initial Equation: K + Br₂ → KBr
- Analysis:
- On the left: 1 K, 2 Br
- On the right: 1 K, 1 Br
- Balancing:
- To balance Br, multiply KBr by 2.
- Balanced Equation: 2K + Br₂ → 2KBr

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5. C₈H₁₈ + O₂ → CO₂ + H₂O

- Initial Equation: C₈H₁₈ + O₂ → CO₂ + H₂O
- Analysis:
- On the left: 8 C, 18 H, 2 O
- On the right: 1 C, 2 O (in CO₂), 2 H, 1 O (in H₂O)
- Balancing:
- Balance C: Multiply CO₂ by 8.
- Balance H: Multiply H₂O by 9.
- Balance O: Multiply O₂ by 25/2 (or 12.5). Since coefficients must be integers, multiply everything by 2.
- Balanced Equation: 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

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6. Sb + I₂ → SbI₃

- Initial Equation: Sb + I₂ → SbI₃
- Analysis:
- On the left: 1 Sb, 2 I
- On the right: 1 Sb, 3 I
- Balancing:
- To balance I, multiply I₂ by 3/2 (or 1.5). Since coefficients must be integers, multiply everything by 2.
- Balanced Equation: 2Sb + 3I₂ → 2SbI₃

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7. COCl₂ + H₂O → HCl + CO₂

- Initial Equation: COCl₂ + H₂O → HCl + CO₂
- Analysis:
- On the left: 1 C, 1 O, 2 Cl, 2 H
- On the right: 1 C, 2 O, 1 Cl, 2 H
- Balancing:
- To balance Cl, multiply HCl by 2.
- Balanced Equation: COCl₂ + H₂O → 2HCl + CO₂

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8. CS₂ + O₂ → CO₂ + SO₂

- Initial Equation: CS₂ + O₂ → CO₂ + SO₂
- Analysis:
- On the left: 1 C, 2 S, 2 O
- On the right: 1 C, 2 O (in CO₂), 2 S, 2 O (in SO₂)
- Balancing:
- Total O on the right is 4. Multiply O₂ by 3/2 (or 1.5). Since coefficients must be integers, multiply everything by 2.
- Balanced Equation: 2CS₂ + 3O₂ → 2CO₂ + 2SO₂

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9. H₂SO₄ + NaCN → HCN + Na₂SO₄

- Initial Equation: H₂SO₄ + NaCN → HCN + Na₂SO₄
- Analysis:
- On the left: 2 H, 1 S, 4 O, 1 Na, 1 C, 1 N
- On the right: 1 H, 1 C, 1 N, 1 S, 4 O, 2 Na
- Balancing:
- To balance Na, multiply NaCN by 2.
- To balance H, multiply HCN by 2.
- Balanced Equation: H₂SO₄ + 2NaCN → 2HCN + Na₂SO₄

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10. KClO₃ → KCl + O₂

- Initial Equation: KClO₃ → KCl + O₂
- Analysis:
- On the left: 1 K, 1 Cl, 3 O
- On the right: 1 K, 1 Cl, 2 O
- Balancing:
- To balance O, multiply O₂ by 3/2 (or 1.5). Since coefficients must be integers, multiply everything by 2.
- Balanced Equation: 2KClO₃ → 2KCl + 3O₂

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11. H₂ + F₂ → HF

- Initial Equation: H₂ + F₂ → HF
- Analysis:
- On the left: 2 H, 2 F
- On the right: 1 H, 1 F
- Balancing:
- To balance H and F, multiply HF by 2.
- Balanced Equation: H₂ + F₂ → 2HF

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12. BaCl₂ + KIO₃ → Ba(IO₃)₂ + KCl

- Initial Equation: BaCl₂ + KIO₃ → Ba(IO₃)₂ + KCl
- Analysis:
- On the left: 1 Ba, 2 Cl, 1 K, 1 I, 3 O
- On the right: 1 Ba, 2 I, 6 O, 1 K, 1 Cl
- Balancing:
- To balance Cl, multiply BaCl₂ by 2.
- To balance I and O, multiply KIO₃ by 2.
- Balanced Equation: BaCl₂ + 2KIO₃ → Ba(IO₃)₂ + 2KCl

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13. Mg + HCl → MgCl₂ + H₂

- Initial Equation: Mg + HCl → MgCl₂ + H₂
- Analysis:
- On the left: 1 Mg, 1 H, 1 Cl
- On the right: 1 Mg, 2 Cl, 2 H
- Balancing:
- To balance Cl, multiply HCl by 2.
- To balance H, multiply H₂ by 1 (already balanced).
- Balanced Equation: Mg + 2HCl → MgCl₂ + H₂

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Final Answer

\[
\boxed{
\begin{aligned}
1. & \quad 3Fe + 2O_2 \rightarrow Fe_3O_4 \\
2. & \quad 2Sr + O_2 \rightarrow 2SrO \\
3. & \quad Sn + 2NaOH \rightarrow Na_2SnO_2 + H_2 \\
4. & \quad 2K + Br_2 \rightarrow 2KBr \\
5. & \quad 2C_8H_{18} + 25O_2 \rightarrow 16CO_2 + 18H_2O \\
6. & \quad 2Sb + 3I_2 \rightarrow 2SbI_3 \\
7. & \quad COCl_2 + H_2O \rightarrow 2HCl + CO_2 \\
8. & \quad 2CS_2 + 3O_2 \rightarrow 2CO_2 + 2SO_2 \\
9. & \quad H_2SO_4 + 2NaCN \rightarrow 2HCN + Na_2SO_4 \\
10. & \quad 2KClO_3 \rightarrow 2KCl + 3O_2 \\
11. & \quad H_2 + F_2 \rightarrow 2HF \\
12. & \quad BaCl_2 + 2KIO_3 \rightarrow Ba(IO_3)_2 + 2KCl \\
13. & \quad Mg + 2HCl \rightarrow MgCl_2 + H_2 \\
\end{aligned}
}
\]