Balancing Chemical Equations - Worksheet 1 | Science 9th Grade - Free Printable

To balance 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 for each problem:

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1. H₃PO₄ + KOH → K₃PO₄ + H₂O

- Start with phosphoric acid (H₃PO₄) and potassium hydroxide (KOH).
- Phosphoric acid has 3 hydrogen atoms, so we need 3 KOH molecules to balance the hydrogen.
- This gives us 3 potassium atoms on the left, so we need 3 potassium atoms on the right in K₃PO₄.
- The oxygen and phosphorus atoms are already balanced.

Balanced Equation:
$$
\boxed{H_3PO_4 + 3KOH \rightarrow K_3PO_4 + 3H_2O}
$$

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2. HCl + NaOH → NaCl + H₂O

- Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH).
- Balance the chlorine atom by having 1 HCl and 1 NaOH.
- This automatically balances the sodium, hydrogen, and oxygen atoms.

Balanced Equation:
$$
\boxed{HCl + NaOH \rightarrow NaCl + H_2O}
$$

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3. Na + NaN₃ → Na₂O + N₂

- Sodium (Na) reacts with sodium azide (NaN₃).
- Balance the sodium atoms first. There are 4 sodium atoms on the left (1 from Na and 3 from NaN₃), so we need 2 Na₂O molecules on the right.
- Balance the nitrogen atoms. There are 3 nitrogen atoms in NaN₃, so we need 3/2 N₂ molecules, which simplifies to 3 N₂ / 2.

Balanced Equation:
$$
\boxed{10Na + 2NaN_3 \rightarrow 6Na_2O + 5N_2}
$$

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4. N₂ + O₂ → N₂O₅

- Nitrogen gas (N₂) reacts with oxygen gas (O₂) to form dinitrogen pentoxide (N₂O₅).
- Balance the nitrogen atoms first. There are 2 nitrogen atoms in N₂ and N₂O₅, so the nitrogen is already balanced.
- Balance the oxygen atoms. There are 5 oxygen atoms in N₂O₅, so we need 5/2 O₂ molecules, which simplifies to 5 O₂ / 2.

Balanced Equation:
$$
\boxed{2N_2 + 5O_2 \rightarrow 2N_2O_5}
$$

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5. H₃PO₄ + Mg(OH)₂ → Mg₃(PO₄)₂ + H₂O

- Phosphoric acid (H₃PO₄) reacts with magnesium hydroxide (Mg(OH)₂).
- Balance the magnesium atoms first. There are 3 magnesium atoms in Mg₃(PO₄)₂, so we need 3 Mg(OH)₂ molecules.
- Balance the phosphate (PO₄) groups. There are 2 PO₄ groups in Mg₃(PO₄)₂, so we need 2 H₃PO₄ molecules.
- Balance the hydrogen and oxygen atoms. This gives us 6 H₂O molecules.

Balanced Equation:
$$
\boxed{2H_3PO_4 + 3Mg(OH)_2 \rightarrow Mg_3(PO_4)_2 + 6H_2O}
$$

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6. NaOH + H₂CO₃ → Na₂CO₃ + H₂O

- Sodium hydroxide (NaOH) reacts with carbonic acid (H₂CO₃).
- Balance the sodium atoms. There are 2 sodium atoms in Na₂CO₃, so we need 2 NaOH molecules.
- Balance the hydrogen and oxygen atoms. This gives us 2 H₂O molecules.

Balanced Equation:
$$
\boxed{2NaOH + H_2CO_3 \rightarrow Na_2CO_3 + 2H_2O}
$$

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7. H₂ + O₂ → H₂O₂

- Hydrogen gas (H₂) reacts with oxygen gas (O₂) to form hydrogen peroxide (H₂O₂).
- Balance the hydrogen atoms. There are 2 hydrogen atoms in H₂ and H₂O₂, so the hydrogen is already balanced.
- Balance the oxygen atoms. There are 2 oxygen atoms in H₂O₂, so we need 1 O₂ molecule.

Balanced Equation:
$$
\boxed{H_2 + O_2 \rightarrow H_2O_2}
$$

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8. Na + O₂ → Na₂O

- Sodium (Na) reacts with oxygen gas (O₂) to form sodium oxide (Na₂O).
- Balance the sodium atoms. There are 2 sodium atoms in Na₂O, so we need 2 Na atoms.
- Balance the oxygen atoms. There is 1 oxygen atom in Na₂O, so we need 1/2 O₂ molecule, which simplifies to 1 O₂ / 2.

Balanced Equation:
$$
\boxed{4Na + O_2 \rightarrow 2Na_2O}
$$

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9. Al + S₈ → Al₂S₃

- Aluminum (Al) reacts with sulfur (S₈) to form aluminum sulfide (Al₂S₃).
- Balance the aluminum atoms. There are 2 aluminum atoms in Al₂S₃, so we need 2 Al atoms.
- Balance the sulfur atoms. There are 3 sulfur atoms in Al₂S₃, so we need 3/8 S₈ molecules, which simplifies to 3 S₈ / 8.

Balanced Equation:
$$
\boxed{2Al + \frac{3}{8}S_8 \rightarrow Al_2S_3}
$$

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10. Cs + N₂ → Cs₃N

- Cesium (Cs) reacts with nitrogen gas (N₂) to form cesium nitride (Cs₃N).
- Balance the cesium atoms. There are 3 cesium atoms in Cs₃N, so we need 3 Cs atoms.
- Balance the nitrogen atoms. There is 1 nitrogen atom in Cs₃N, so we need 1/2 N₂ molecule, which simplifies to 1 N₂ / 2.

Balanced Equation:
$$
\boxed{6Cs + N_2 \rightarrow 2Cs_3N}
$$

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11. Mg + Cl₂ → MgCl₂

- Magnesium (Mg) reacts with chlorine gas (Cl₂) to form magnesium chloride (MgCl₂).
- Balance the magnesium atoms. There is 1 magnesium atom in MgCl₂, so we need 1 Mg atom.
- Balance the chlorine atoms. There are 2 chlorine atoms in MgCl₂, so we need 1 Cl₂ molecule.

Balanced Equation:
$$
\boxed{Mg + Cl_2 \rightarrow MgCl_2}
$$

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12. Rb + RbNO₃ → Rb₂O + N₂

- Rubidium (Rb) reacts with rubidium nitrate (RbNO₃) to form rubidium oxide (Rb₂O) and nitrogen gas (N₂).
- Balance the rubidium atoms. There are 2 rubidium atoms in Rb₂O, so we need 2 Rb atoms.
- Balance the nitrogen atoms. There is 1 nitrogen atom in RbNO₃ and 2 nitrogen atoms in N₂, so we need 2 RbNO₃ molecules.
- Balance the oxygen atoms. This gives us 3 Rb₂O molecules.

Balanced Equation:
$$
\boxed{6Rb + 2RbNO_3 \rightarrow 3Rb_2O + N_2}
$$

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13. C₆H₆ + O₂ → CO₂ + H₂O

- Benzene (C₆H₆) reacts with oxygen gas (O₂) to form carbon dioxide (CO₂) and water (H₂O).
- Balance the carbon atoms. There are 6 carbon atoms in C₆H₆, so we need 6 CO₂ molecules.
- Balance the hydrogen atoms. There are 6 hydrogen atoms in C₆H₆, so we need 3 H₂O molecules.
- Balance the oxygen atoms. This gives us 15/2 O₂ molecules, which simplifies to 15 O₂ / 2.

Balanced Equation:
$$
\boxed{2C_6H_6 + 15O_2 \rightarrow 12CO_2 + 6H_2O}
$$

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14. N₂ + H₂ → NH₃

- Nitrogen gas (N₂) reacts with hydrogen gas (H₂) to form ammonia (NH₃).
- Balance the nitrogen atoms. There are 2 nitrogen atoms in N₂ and 1 nitrogen atom in NH₃, so we need 2 NH₃ molecules.
- Balance the hydrogen atoms. There are 6 hydrogen atoms in 2 NH₃ molecules, so we need 3 H₂ molecules.

Balanced Equation:
$$
\boxed{N_2 + 3H_2 \rightarrow 2NH_3}
$$

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15. C + O₂ → CO₂

- Carbon (C) reacts with oxygen gas (O₂) to form carbon dioxide (CO₂).
- Balance the carbon atoms. There is 1 carbon atom in CO₂, so we need 1 C atom.
- Balance the oxygen atoms. There are 2 oxygen atoms in CO₂, so we need 1 O₂ molecule.

Balanced Equation:
$$
\boxed{C + O_2 \rightarrow CO_2}
$$

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16. C₃H₈ + O₂ → CO₂ + H₂O

- Propane (C₃H₈) reacts with oxygen gas (O₂) to form carbon dioxide (CO₂) and water (H₂O).
- Balance the carbon atoms. There are 3 carbon atoms in C₃H₈, so we need 3 CO₂ molecules.
- Balance the hydrogen atoms. There are 8 hydrogen atoms in C₃H₈, so we need 4 H₂O molecules.
- Balance the oxygen atoms. This gives us 5 O₂ molecules.

Balanced Equation:
$$
\boxed{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}
$$

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17. Li + AlCl₃ → LiCl + Al

- Lithium (Li) reacts with aluminum chloride (AlCl₃) to form lithium chloride (LiCl) and aluminum (Al).
- Balance the lithium atoms. There are 3 lithium atoms in 3 LiCl molecules, so we need 3 Li atoms.
- Balance the aluminum atoms. There is 1 aluminum atom in AlCl₃ and Al, so we need 1 AlCl₃ molecule.
- Balance the chlorine atoms. This gives us 3 LiCl molecules.

Balanced Equation:
$$
\boxed{3Li + AlCl_3 \rightarrow 3LiCl + Al}
$$

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18. Rb + P → Rb₃P

- Rubidium (Rb) reacts with phosphorus (P) to form rubidium phosphide (Rb₃P).
- Balance the rubidium atoms. There are 3 rubidium atoms in Rb₃P, so we need 3 Rb atoms.
- Balance the phosphorus atoms. There is 1 phosphorus atom in Rb₃P, so we need 1 P atom.

Balanced Equation:
$$
\boxed{3Rb + P \rightarrow Rb_3P}
$$

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19. Al(OH)₃ + H₂SO₄ → Al₂(SO₄)₃ + H₂O

- Aluminum hydroxide (Al(OH)₃) reacts with sulfuric acid (H₂SO₄) to form aluminum sulfate (Al₂(SO₄)₃) and water (H₂O).
- Balance the aluminum atoms. There are 2 aluminum atoms in Al₂(SO₄)₃, so we need 2 Al(OH)₃ molecules.
- Balance the sulfate (SO₄) groups. There are 3 SO₄ groups in Al₂(SO₄)₃, so we need 3 H₂SO₄ molecules.
- Balance the hydrogen and oxygen atoms. This gives us 6 H₂O molecules.

Balanced Equation:
$$
\boxed{2Al(OH)_3 + 3H_2SO_4 \rightarrow Al_2(SO_4)_3 + 6H_2O}
$$

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20. Rb + S₈ → Rb₂S

- Rubidium (Rb) reacts with sulfur (S₈) to form rubidium sulfide (Rb₂S).
- Balance the rubidium atoms. There are 2 rubidium atoms in Rb₂S, so we need 2 Rb atoms.
- Balance the sulfur atoms. There is 1 sulfur atom in Rb₂S, so we need 1/8 S₈ molecule, which simplifies to 1 S₈ / 8.

Balanced Equation:
$$
\boxed{2Rb + \frac{1}{8}S_8 \rightarrow Rb_2S}
$$

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21. CaSO₄ + KOH → Ca(OH)₂ + K₂SO₄

- Calcium sulfate (CaSO₄) reacts with potassium hydroxide (KOH) to form calcium hydroxide (Ca(OH)₂) and potassium sulfate (K₂SO₄).
- Balance the calcium atoms. There is 1 calcium atom in CaSO₄ and Ca(OH)₂, so the calcium is already balanced.
- Balance the potassium atoms. There are 2 potassium atoms in K₂SO₄, so we need 2 KOH molecules.
- Balance the sulfur and oxygen atoms. This gives us 1 K₂SO₄ molecule.

Balanced Equation:
$$
\boxed{CaSO_4 + 2KOH \rightarrow Ca(OH)_2 + K_2SO_4}
$$

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22. FeBr₃ + Na → Fe + NaBr

- Iron(III) bromide (FeBr₃) reacts with sodium (Na) to form iron (Fe) and sodium bromide (NaBr).
- Balance the iron atoms. There is 1 iron atom in FeBr₃ and Fe, so the iron is already balanced.
- Balance the bromine atoms. There are 3 bromine atoms in FeBr₃, so we need 3 NaBr molecules.
- Balance the sodium atoms. This gives us 3 Na atoms.

Balanced Equation:
$$
\boxed{FeBr_3 + 3Na \rightarrow Fe + 3NaBr}
$$

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23. Al₄C₃ + H₂O → CH₄ + Al(OH)₃

- Aluminum carbide (Al₄C₃) reacts with water (H₂O) to form methane (CH₄) and aluminum hydroxide (Al(OH)₃).
- Balance the aluminum atoms. There are 4 aluminum atoms in Al₄C₃, so we need 4 Al(OH)₃ molecules.
- Balance the carbon atoms. There are 3 carbon atoms in Al₄C₃, so we need 3 CH₄ molecules.
- Balance the hydrogen and oxygen atoms. This gives us 12 H₂O molecules.

Balanced Equation:
$$
\boxed{Al_4C_3 + 12H_2O \rightarrow 3CH_4 + 4Al(OH)_3}
$$

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24. Ba + HNO₃ → H₂ + Ba(NO₃)₂

- Barium (Ba) reacts with nitric acid (HNO₃) to form hydrogen gas (H₂) and barium nitrate (Ba(NO₃)₂).
- Balance the barium atoms. There is 1 barium atom in Ba and Ba(NO₃)₂, so the barium is already balanced.
- Balance the hydrogen atoms. There are 2 hydrogen atoms in H₂, so we need 2 HNO₃ molecules.
- Balance the nitrogen and oxygen atoms. This gives us 1 Ba(NO₃)₂ molecule.

Balanced Equation:
$$
\boxed{Ba + 2HNO_3 \rightarrow H_2 + Ba(NO_3)_2}
$$

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25. NH₄OH + HBr → H₂O + NH₄Br

- Ammonium hydroxide (NH₄OH) reacts with hydrobromic acid (HBr) to form water (H₂O) and ammonium bromide (NH₄Br).
- Balance the nitrogen atoms. There is 1 nitrogen atom in NH₄OH and NH₄Br, so the nitrogen is already balanced.
- Balance the hydrogen atoms. There are 5 hydrogen atoms in NH₄OH and HBr, so we need 1 H₂O molecule.
- Balance the bromine atoms. There is 1 bromine atom in HBr and NH₄Br, so the bromine is already balanced.

Balanced Equation:
$$
\boxed{NH_4OH + HBr \rightarrow H_2O + NH_4Br}
$$

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Final Answer:

$$
\boxed{
\begin{aligned}
1. & \quad H_3PO_4 + 3KOH \rightarrow K_3PO_4 + 3H_2O \\
2. & \quad HCl + NaOH \rightarrow NaCl + H_2O \\
3. & \quad 10Na + 2NaN_3 \rightarrow 6Na_2O + 5N_2 \\
4. & \quad 2N_2 + 5O_2 \rightarrow 2N_2O_5 \\
5. & \quad 2H_3PO_4 + 3Mg(OH)_2 \rightarrow Mg_3(PO_4)_2 + 6H_2O \\
6. & \quad 2NaOH + H_2CO_3 \rightarrow Na_2CO_3 + 2H_2O \\
7. & \quad H_2 + O_2 \rightarrow H_2O_2 \\
8. & \quad 4Na + O_2 \rightarrow 2Na_2O \\
9. & \quad 2Al + \frac{3}{8}S_8 \rightarrow Al_2S_3 \\
10. & \quad 6Cs + N_2 \rightarrow 2Cs_3N \\
11. & \quad Mg + Cl_2 \rightarrow MgCl_2 \\
12. & \quad 6Rb + 2RbNO_3 \rightarrow 3Rb_2O + N_2 \\
13. & \quad 2C_6H_6 + 15O_2 \rightarrow 12CO_2 + 6H_2O \\
14. & \quad N_2 + 3H_2 \rightarrow 2NH_3 \\
15. & \quad C + O_2 \rightarrow CO_2 \\
16. & \quad C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O \\
17. & \quad 3Li + AlCl_3 \rightarrow 3LiCl + Al \\
18. & \quad 3Rb + P \rightarrow Rb_3P \\
19. & \quad 2Al(OH)_3 + 3H_2SO_4 \rightarrow Al_2(SO_4)_3 + 6H_2O \\
20. & \quad 2Rb + \frac{1}{8}S_8 \rightarrow Rb_2S \\
21. & \quad CaSO_4 + 2KOH \rightarrow Ca(OH)_2 + K_2SO_4 \\
22. & \quad FeBr_3 + 3Na \rightarrow Fe + 3NaBr \\
23. & \quad Al_4C_3 + 12H_2O \rightarrow 3CH_4 + 4Al(OH)_3 \\
24. & \quad Ba + 2HNO_3 \rightarrow H_2 + Ba(NO_3)_2 \\
25. & \quad NH_4OH + HBr \rightarrow H_2O + NH_4Br \\
\end{aligned}
}
$$