Let’s go through each decomposition reaction one by one. In a decomposition reaction, one compound breaks down into two or more simpler substances — often elements or smaller compounds. We’ll use common patterns for each type of compound.
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1. barium carbonate →
Carbonates (like BaCO₃) usually break down into metal oxide + carbon dioxide when heated.
→ Barium oxide + carbon dioxide
BaCO₃ → BaO + CO₂
2. magnesium carbonate →
Same pattern: MgCO₃ → MgO + CO₂
3. potassium carbonate →
Potassium is very reactive — its carbonate does NOT decompose easily with heat alone. But in many school worksheets, they still expect:
K₂CO₃ → K₂O + CO₂ *(Note: This doesn’t happen readily in real life, but it’s often accepted in basic chem classes)*
4. zinc hydroxide →
Hydroxides of metals like Zn break down into metal oxide + water.
Zn(OH)₂ → ZnO + H₂O
5. Iron(II) hydroxide →
Fe(OH)₂ → FeO + H₂O
*(Sometimes it can form Fe₂O₃ if oxidized, but for simple decomposition, FeO is fine here.)*
6. nickel(II) chlorate →
Chlorates (ClO₃⁻) break down into chloride + oxygen gas.
Ni(ClO₃)₂ → NiCl₂ + O₂
But we need to balance it:
2Ni(ClO₃)₂ → 2NiCl₂ + 3O₂? Wait — let’s check atoms.
Actually, standard decomposition: Metal chlorate → metal chloride + oxygen
So: Ni(ClO₃)₂ → NiCl₂ + 3O₂? Let’s count:
Left: Ni=1, Cl=2, O=6
Right: Ni=1, Cl=2, O=6 → YES! So:
Ni(ClO₃)₂ → NiCl₂ + 3O₂
Wait — that’s not balanced for oxygen? 3O₂ = 6 oxygen atoms — yes, matches left side. Good.
7. sodium chlorate →
NaClO₃ → NaCl + O₂
Balance: 2NaClO₃ → 2NaCl + 3O₂
8. potassium chlorate →
Same as above: 2KClO₃ → 2KCl + 3O₂
9. sulfuric acid →
H₂SO₄ can decompose into SO₃ + H₂O (when concentrated and heated)
H₂SO₄ → SO₃ + H₂O
10. carbonic acid →
Very unstable — breaks into water and CO₂
H₂CO₃ → H₂O + CO₂
11. aluminum oxide →
Aluminum oxide is VERY stable — doesn’t decompose easily. But if forced (electrolysis), it gives aluminum metal and oxygen.
In basic chem, sometimes they write:
2Al₂O₃ → 4Al + 3O₂
*(This requires electricity, not just heat — but again, worksheet may accept this.)*
12. silver oxide →
Ag₂O → 2Ag + O₂? Balance:
2Ag₂O → 4Ag + O₂
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Now let’s write all answers clearly:
Final Answer:
1. barium carbonate → barium oxide + carbon dioxide
2. magnesium carbonate → magnesium oxide + carbon dioxide
3. potassium carbonate → potassium oxide + carbon dioxide
4. zinc hydroxide → zinc oxide + water
5. iron(II) hydroxide → iron(II) oxide + water
6. nickel(II) chlorate → nickel(II) chloride + oxygen
7. sodium chlorate → sodium chloride + oxygen
8. potassium chlorate → potassium chloride + oxygen
9. sulfuric acid → sulfur trioxide + water
10. carbonic acid → water + carbon dioxide
11. aluminum oxide → aluminum + oxygen
12. silver oxide → silver + oxygen
*(Note: For #3, #11 — these don’t actually decompose easily under normal lab conditions, but are commonly listed this way in introductory chemistry worksheets.)*
Parent Tip: Review the logic above to help your child master the concept of decomposition worksheet.
