Identifying and Balancing Chemical Reactions worksheet for students to practice determining reaction types and balancing equations.

Let's go through each chemical reaction one by one. For each, we'll:

1. Identify the type of reaction (e.g., synthesis, decomposition, single displacement, double displacement, combustion, etc.).
2. Balance the chemical equation.

---

(i)

Unbalanced:
$$ \text{Na}_2\text{CO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{CO}_3 $$

- Type of Reaction: Double Displacement (also called metathesis). Two compounds exchange ions.
- Balancing:
- Na: 2 on left → need 2 NaCl on right
- Cl: 2 on right → need 2 HCl on left
- H and CO₃: H₂CO₃ already matches with 2 H and 1 CO₃

$$
\boxed{\text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{CO}_3}
$$

> Note: H₂CO₃ decomposes into H₂O and CO₂, but that’s not asked here.

---

(ii)

Unbalanced:
$$ \text{NH}_4\text{NO}_2 \rightarrow \text{N}_2 + \text{H}_2\text{O} $$

- Type of Reaction: Decomposition — one compound breaks down into two or more substances.
- Balancing:
- N: 2 on left → 1 N₂ on right (good)
- H: 4 on left → need 2 H₂O on right
- O: 2 on left → 2 H₂O has 2 O → good

$$
\boxed{\text{NH}_4\text{NO}_2 \rightarrow \text{N}_2 + 2\text{H}_2\text{O}}
$$

---

(iii)

Unbalanced:
$$ \text{N}_2 + \text{O}_2 \rightarrow \text{N}_2\text{O}_5 $$

- Type of Reaction: Synthesis (combination) — two elements combine to form a compound.
- Balancing:
- N: 2 on both sides → okay
- O: 2 on left, 5 on right → LCM of 2 and 5 is 10
- Use 2 N₂O₅ → 4 N, 10 O → need 2 N₂ and 5 O₂

$$
\boxed{2\text{N}_2 + 5\text{O}_2 \rightarrow 2\text{N}_2\text{O}_5}
$$

---

(iv)

Unbalanced:
$$ \text{MgCO}_3 \rightarrow \text{MgO} + \text{CO}_2 $$

- Type of Reaction: Decomposition — carbonate breaks into metal oxide and CO₂.
- Already balanced:
- Mg: 1
- C: 1
- O: 3 → 1 in MgO + 2 in CO₂ = 3

$$
\boxed{\text{MgCO}_3 \rightarrow \text{MgO} + \text{CO}_2}
$$

---

(v)

Unbalanced:
$$ \text{KBr} + \text{Cl}_2 \rightarrow \text{KCl} + \text{Br}_2 $$

- Type of Reaction: Single Displacement — more reactive halogen (Cl₂) displaces Br⁻ from KBr.
- Balancing:
- Cl₂ → 2 Cl atoms → need 2 KCl
- So 2 KBr on left → 2 Br → Br₂ on right

$$
\boxed{2\text{KBr} + \text{Cl}_2 \rightarrow 2\text{KCl} + \text{Br}_2}
$$

---

(vi)

Unbalanced:
$$ \text{Zn} + \text{CuSO}_4 \rightarrow \text{Cu} + \text{ZnSO}_4 $$

- Type of Reaction: Single Displacement — Zn displaces Cu²⁺ from its salt.
- Already balanced:
- Zn: 1
- Cu: 1
- S: 1
- O: 4

$$
\boxed{\text{Zn} + \text{CuSO}_4 \rightarrow \text{Cu} + \text{ZnSO}_4}
$$

---

(vii)

Unbalanced:
$$ \text{P} + \text{O}_2 \rightarrow \text{P}_4\text{O}_6 $$

- Type of Reaction: Synthesis — phosphorus combines with oxygen.
- Balancing:
- P₄O₆ contains 4 P atoms → need 4 P on left
- O: 6 on right → need 3 O₂ molecules

$$
\boxed{4\text{P} + 3\text{O}_2 \rightarrow \text{P}_4\text{O}_6}
$$

---

(viii)

Unbalanced:
$$ \text{SrBr}_2 + (\text{NH}_4)_2\text{CO}_3 \rightarrow \text{SrCO}_3 + \text{NH}_4\text{Br} $$

- Type of Reaction: Double Displacement — ions swap partners.
- Balancing:
- Sr: 1
- CO₃: 1
- NH₄: 2 on left → need 2 NH₄Br on right
- Br: 2 on left → 2 NH₄Br → good

$$
\boxed{\text{SrBr}_2 + (\text{NH}_4)_2\text{CO}_3 \rightarrow \text{SrCO}_3 + 2\text{NH}_4\text{Br}}
$$

---

(ix)

Unbalanced:
$$ \text{AgNO}_3 + (\text{NH}_4)_2\text{CrO}_4 \rightarrow \text{Ag}_2\text{CrO}_4 + \text{NH}_4\text{NO}_3 $$

- Type of Reaction: Double Displacement
- Balancing:
- Ag: 2 on right → need 2 AgNO₃ on left
- CrO₄: 1 → okay
- NH₄: 2 on left → need 2 NH₄NO₃ on right
- NO₃: 2 on left → 2 on right → good

$$
\boxed{2\text{AgNO}_3 + (\text{NH}_4)_2\text{CrO}_4 \rightarrow \text{Ag}_2\text{CrO}_4 + 2\text{NH}_4\text{NO}_3}
$$

---

(x)

Unbalanced:
$$ \text{K} + \text{H}_2\text{O} \rightarrow \text{KOH} + \text{H}_2 $$

- Type of Reaction: Single Displacement — K displaces H from water.
- Balancing:
- K: 1
- H: 2 on left → 1 in KOH and 2 in H₂ → total 3 H? Wait.
- Let’s balance:
- Left: K, 2H, 1O
- Right: KOH (K, O, H), H₂ (2H) → total 3H → too many

Try:
- 2K + 2H₂O → 2KOH + H₂
- K: 2 = 2
- H: 4 on left → 2 in 2KOH + 2 in H₂ = 4 → good
- O: 2 = 2

$$
\boxed{2\text{K} + 2\text{H}_2\text{O} \rightarrow 2\text{KOH} + \text{H}_2}
$$

---

(xi)

Unbalanced:
$$ \text{Al} + \text{Pb(NO}_3)_2 \rightarrow \text{Al(NO}_3)_3 + \text{Pb} $$

- Type of Reaction: Single Displacement — Al displaces Pb²⁺
- Balancing:
- Al: 1 → 1
- Pb: 1 → 1
- NO₃: 2 on left, 3 on right → LCM = 6
- Use 3 Pb(NO₃)₂ → 6 NO₃ → need 2 Al(NO₃)₃
- So 2 Al on left

$$
\boxed{2\text{Al} + 3\text{Pb(NO}_3)_2 \rightarrow 2\text{Al(NO}_3)_3 + 3\text{Pb}}
$$

---

(xii)

Unbalanced:
$$ \text{Fe} + \text{O}_2 \rightarrow \text{Fe}_3\text{O}_4 $$

- Type of Reaction: Synthesis — iron reacts with oxygen.
- Balancing:
- Fe: 3 on right → need 3 Fe on left
- O: 4 on right → need 2 O₂ → 4 O atoms

$$
\boxed{3\text{Fe} + 2\text{O}_2 \rightarrow \text{Fe}_3\text{O}_4}
$$

---

## ✔ Final Summary Table:

| # | Equation | Type of Reaction | Balanced Equation |
|---|---------|------------------|-------------------|
| (i) | Na₂CO₃ + HCl → NaCl + H₂CO₃ | Double Displacement | Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃ |
| (ii) | NH₄NO₂ → N₂ + H₂O | Decomposition | NH₄NO₂ → N₂ + 2H₂O |
| (iii) | N₂ + O₂ → N₂O₅ | Synthesis | 2N₂ + 5O₂ → 2N₂O₅ |
| (iv) | MgCO₃ → MgO + CO₂ | Decomposition | MgCO₃ → MgO + CO₂ |
| (v) | KBr + Cl₂ → KCl + Br₂ | Single Displacement | 2KBr + Cl₂ → 2KCl + Br₂ |
| (vi) | Zn + CuSO₄ → Cu + ZnSO₄ | Single Displacement | Zn + CuSO₄ → Cu + ZnSO₄ |
| (vii) | P + O₂ → P₄O₆ | Synthesis | 4P + 3O₂ → P₄O₆ |
| (viii) | SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + NH₄Br | Double Displacement | SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + 2NH₄Br |
| (ix) | AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + NH₄NO₃ | Double Displacement | 2AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + 2NH₄NO₃ |
| (x) | K + H₂O → KOH + H₂ | Single Displacement | 2K + 2H₂O → 2KOH + H₂ |
| (xi) | Al + Pb(NO₃)₂ → Al(NO₃)₃ + Pb | Single Displacement | 2Al + 3Pb(NO₃)₂ → 2Al(NO₃)₃ + 3Pb |
| (xii) | Fe + O₂ → Fe₃O₄ | Synthesis | 3Fe + 2O₂ → Fe₃O₄ |

---

Let me know if you'd like this as a printable PDF or need explanations for any specific step!