Worksheet for writing and balancing chemical equations based on word descriptions.

Let’s solve each problem step by step. We’ll write the chemical formulas, balance the charges to make neutral compounds, then balance the whole equation so atoms are equal on both sides.

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Problem 1: zinc metal reacts lead(II) nitrate to yield zinc nitrate and lead metal.

Step 1: Write correct formulas.

- Zinc metal = Zn (elemental form)
- Lead(II) nitrate → Pb²⁺ and NO₃⁻ → Pb(NO₃)₂ (because you need two nitrates to balance +2 charge)
- Zinc nitrate → Zn²⁺ and NO⁻ → Zn(NO₃)₂
- Lead metal = Pb (elemental form)

Unbalanced equation:
Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb

Step 2: Check if it’s already balanced.

Left side:
Zn: 1
Pb: 1
N: 2 (from Pb(NO₃)₂)
O: 6 (3×2 from two NO₃ groups)

Right side:
Zn: 1
Pb: 1
N: 2 (from Zn(NO₃)₂)
O: 6

✔ Already balanced!

Final answer for #1:
Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb

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Problem 2: aluminum bromide and chlorine gas yields aluminum chloride and liquid bromine

Step 1: Write correct formulas.

- Aluminum bromide → Al³⁺ and Br⁻ → AlBr₃
- Chlorine gas → Cl₂ (diatomic element)
- Aluminum chloride → Al³⁺ and Cl⁻ → AlCl₃
- Liquid bromine → Br₂ (diatomic element in liquid state)

Unbalanced equation:
AlBr₃ + Cl₂ → AlCl₃ + Br₂

Step 2: Balance atoms.

Look at Br: left has 3, right has 2 → LCM is 6 → put 2 in front of AlBr₃ and 3 in front of Br₂

Now:
2AlBr₃ + Cl₂ → AlCl₃ + 3Br₂

Check Al: left has 2, right has 1 → put 2 in front of AlCl₃

Now:
2AlBr₃ + Cl₂ → 2AlCl₃ + 3Br₂

Check Cl: right has 6 (2×3), left has 2 → put 3 in front of Cl₂

Now:
2AlBr₃ + 3Cl₂ → 2AlCl₃ + 3Br₂

Check all:

Left:
Al: 2
Br: 6
Cl: 6

Right:
Al: 2
Cl: 6
Br: 6

✔ Balanced!

Final answer for #2:
2AlBr₃ + 3Cl₂ → 2AlCl₃ + 3Br₂

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Problem 3: sodium phosphate and calcium chloride yields calcium phosphate and sodium chloride

Step 1: Write correct formulas.

- Sodium phosphate → Na⁺ and PO₄³⁻ → Na₃PO₄ (need 3 Na⁺ to balance -3)
- Calcium chloride → Ca²⁺ and Cl⁻ → CaCl₂
- Calcium phosphate → Ca²⁺ and PO₄³⁻ → Ca(PO₄)₂ (LCM of 2 and 3 is 6 → 3 Ca²⁺ and 2 PO₄³⁻)
- Sodium chloride → Na⁺ and Cl → NaCl

Unbalanced equation:
Na₃PO₄ + CaCl₂ → Ca₃(PO₄)₂ + NaCl

Step 2: Balance atoms.

Start with PO₄: left has 1, right has 2 → put 2 in front of Na₃PO₄

Now:
2Na₃PO₄ + CaCl₂ → Ca₃(PO)₂ + NaCl

Now Na: left has 6 (2×3), right has 1 → put 6 in front of NaCl

Now:
2Na₃PO₄ + CaCl₂ → Ca₃(PO₄)₂ + 6NaCl

Now Cl: right has 6, left has 2 → put 3 in front of CaCl₂

Now:
2Na₃PO₄ + 3CaCl₂ → Ca₃(PO₄)₂ + 6NaCl

Check Ca: left has 3, right has 3 → good

Check everything:

Left:
Na: 6
P: 2
O: 8 (4×2)
Ca: 3
Cl: 6

Right:
Ca: 3
P: 2
O: 8
Na: 6
Cl: 6

✔ Balanced!

Final answer for #3:
2Na₃PO₄ + 3CaCl₂ → Ca₃(PO₄)₂ + 6NaCl

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Final Answer:
1) Zn + Pb(NO₃)₂ → Zn(NO₃)₂ + Pb
2) 2AlBr₃ + 3Cl₂ → 2AlCl₃ + 3Br₂
3) 2Na₃PO₄ + 3CaCl₂ → Ca₃(PO₄)₂ + 6NaCl