Free Printable Balancing and Classifying Chemical Equations Worksheets - Free Printable
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Step-by-step solution for: Free Printable Balancing and Classifying Chemical Equations Worksheets
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Show Answer Key & Explanations
Step-by-step solution for: Free Printable Balancing and Classifying Chemical Equations Worksheets
Let’s go through each reaction one by one. For each, we’ll:
1. Balance the equation (make sure atoms on left = atoms on right).
2. Identify the type of reaction.
We’ll use simple rules for reaction types:
- Synthesis: Two or more things combine to make one product. A + B → AB
- Decomposition: One thing breaks into two or more products. AB → A + B
- Single Replacement: One element swaps with another in a compound. A + BC → AC + B
- Double Replacement: Two compounds swap partners. AB + CD → AD + CB
- Combustion: Usually involves O₂ and makes CO₂ and H₂O (but not always — sometimes just oxides)
- Acid-Base / Neutralization: Acid + Base → Salt + Water (a special double replacement)
---
(i) Na₂CO₃ + HCl → NaCl + H₂CO₃
First, balance it.
Left: Na=2, C=1, O=3, H=1, Cl=1
Right: Na=1, Cl=1, H=2, C=1, O=3
Need 2 NaCl on right to match Na from left.
→ Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃
Now check:
Left: Na=2, C=1, O=3, H=2, Cl=2
Right: Na=2, Cl=2, H=2, C=1, O=3 → Balanced!
Type: Double replacement — ions swapped between Na₂CO₃ and HCl.
---
(ii) NH₄NO₂ → N₂ + H₂O
Balance:
Left: N=2, H=4, O=2
Right: N=2, H=2, O=1 → Need 2 H₂O
→ NH₄NO₂ → N₂ + 2H₂O
Check: Left: N=2, H=4, O=2; Right: N=2, H=4, O=2 → Balanced!
Type: Decomposition — one compound breaks into two simpler substances.
---
(iii) N₂ + O₂ → N₂O₅
Balance:
Left: N=2, O=2
Right: N=2, O=5 → Not balanced.
Find LCM of oxygen: 2 and 5 → 10
So try 5 O₂ on left → 10 O atoms
Then need 2 N₂O₅ on right → 4 N and 10 O
But left has only 2 N → so put 2 N₂ on left.
→ 2N₂ + 5O₂ → 2N₂O₅
Check: Left: N=4, O=10; Right: N=4, O=10 → Balanced!
Type: Synthesis — two elements combine to form one compound.
---
(iv) MgCO₃ → MgO + CO₂
Already balanced?
Left: Mg=1, C=1, O=3
Right: Mg=1, O=1+2=3, C=1 → Yes!
Type: Decomposition — one compound breaks into two.
---
(v) KBr + Cl₂ → KCl + Br₂
Balance:
Left: K=1, Br=1, Cl=2
Right: K=1, Cl=1, Br=2 → Need 2 KBr and 2 KCl
→ 2KBr + Cl₂ → 2KCl + Br₂
Check: Left: K=2, Br=2, Cl=2; Right: K=2, Cl=2, Br=2 → Balanced!
Type: Single replacement — Cl replaces Br in compound.
---
(vi) Zn + CuSO₄ → Cu + ZnSO₄
Already balanced?
Left: Zn=1, Cu=1, S=1, O=4
Right: Cu=1, Zn=1, S=1, O=4 → Yes!
Type: Single replacement — Zn replaces Cu.
---
(vii) P + O₂ → P₄O₆
Balance:
Left: P=1, O=2
Right: P=4, O=6
Need 4 P on left → 4P
Need 3 O₂ on left → 6 O atoms
→ 4P + 3O₂ → P₄O₆
Check: Left: P=4, O=6; Right: P=4, O=6 → Balanced!
Type: Synthesis — elements combine to form compound.
---
(viii) SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + NH₄Br
Balance:
Left: Sr=1, Br=2, N=2, H=8, C=1, O=3
Right: Sr=1, C=1, O=3, N=1, H=4, Br=1 → Need 2 NH₄Br
→ SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + 2NH₄Br
Check: Left: Sr=1, Br=2, N=2, H=8, C=1, O=3
Right: Sr=1, C=1, O=3, N=2, H=8, Br=2 → Balanced!
Type: Double replacement — ions swapped.
---
(ix) AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + NH₄NO₃
Balance:
Left: Ag=1, N=1+2=3? Wait — let's count carefully.
AgNO₃: Ag=1, N=1, O=3
(NH₄)₂CrO₄: N=2, H=8, Cr=1, O=4
Total left: Ag=1, N=3, H=8, Cr=1, O=7
Right: Ag₂CrO₄: Ag=2, Cr=1, O=4
NH₄NO₃: N=2, H=4, O=3 → Total right: Ag=2, Cr=1, O=7, N=2, H=4
Not balanced. Need 2 AgNO₃ on left → gives 2 Ag, 2 N, 6 O
Plus (NH₄)₂CrO₄ → adds 2 N, 8 H, 1 Cr, 4 O → total left: Ag=2, N=4, H=8, Cr=1, O=10
Right: Ag₂CrO₄ → Ag=2, Cr=1, O=4
Need 2 NH₄NO₃ → N=4, H=8, O=6 → total right: Ag=2, Cr=1, O=10, N=4, H=8 → Balanced!
→ 2AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + 2NH₄NO₃
Type: Double replacement.
---
(x) K + H₂O → KOH + H₂
Balance:
Left: K=1, H=2, O=1
Right: K=1, O=1, H=1+2=3? Wait — KOH has H=1, H₂ has H=2 → total H=3
Not balanced. Try 2K + 2H₂O → 2KOH + H₂
Left: K=2, H=4, O=2
Right: K=2, O=2, H=2 (from 2KOH) + 2 (from H₂) = 4 → Balanced!
→ 2K + 2H₂O → 2KOH + H₂
Type: Single replacement — K replaces H in water.
---
(xi) Al + Pb₂(NO₃)₂ → Al(NO₃)₃ + Pb
Balance:
Left: Al=1, Pb=2, N=2, O=6
Right: Al=1, N=3, O=9, Pb=1 → Not balanced.
Need to balance NO₃ groups. LCM of 2 and 3 is 6.
So put 3 Pb₂(NO₃)₂ → gives 6 Pb, 6 N, 18 O? Wait — better way:
Set coefficient for Al(NO₃)₃ as 2 → then need 6 NO₃ on left → so 3 Pb₂(NO₃)₂ → but that gives 6 Pb.
Then need 6 Pb on right.
And Al: if 2 Al(NO₃)₃, need 2 Al on left.
Try:
2Al + 3Pb₂(NO₃)₂ → 2Al(NO₃)₃ + 6Pb
Check:
Left: Al=2, Pb=6, N=6, O=18
Right: Al=2, N=6, O=18, Pb=6 → Balanced!
Type: Single replacement — Al replaces Pb.
---
(xii) Fe + O₂ → Fe₃O
Balance:
Left: Fe=1, O=2
Right: Fe=3, O=4
LCM of O: 4 → so 2 O₂ on left → 4 O
Need 3 Fe on left → 3Fe
→ 3Fe + 2O₂ → Fe₃O₄
Check: Left: Fe=3, O=4; Right: Fe=3, O=4 → Balanced!
Type: Synthesis — elements combine.
---
Final Answer:
(i) Balanced: Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃ ; Type: Double Replacement
(ii) Balanced: NH₄NO₂ → N₂ + 2H₂O ; Type: Decomposition
(iii) Balanced: 2N₂ + 5O₂ → 2N₂O₅ ; Type: Synthesis
(iv) Balanced: MgCO₃ → MgO + CO₂ ; Type: Decomposition
(v) Balanced: 2KBr + Cl₂ → 2KCl + Br₂ ; Type: Single Replacement
(vi) Balanced: Zn + CuSO₄ → Cu + ZnSO₄ ; Type: Single Replacement
(vii) Balanced: 4P + 3O₂ → P₄O₆ ; Type: Synthesis
(viii) Balanced: SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + 2NH₄Br ; Type: Double Replacement
(ix) Balanced: 2AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + 2NH₄NO₃ ; Type: Double Replacement
(x) Balanced: 2K + 2H₂O → 2KOH + H₂ ; Type: Single Replacement
(xi) Balanced: 2Al + 3Pb₂(NO₃)₂ → 2Al(NO₃)₃ + 6Pb ; Type: Single Replacement
(xii) Balanced: 3Fe + 2O₂ → Fe₃O₄ ; Type: Synthesis
1. Balance the equation (make sure atoms on left = atoms on right).
2. Identify the type of reaction.
We’ll use simple rules for reaction types:
- Synthesis: Two or more things combine to make one product. A + B → AB
- Decomposition: One thing breaks into two or more products. AB → A + B
- Single Replacement: One element swaps with another in a compound. A + BC → AC + B
- Double Replacement: Two compounds swap partners. AB + CD → AD + CB
- Combustion: Usually involves O₂ and makes CO₂ and H₂O (but not always — sometimes just oxides)
- Acid-Base / Neutralization: Acid + Base → Salt + Water (a special double replacement)
---
(i) Na₂CO₃ + HCl → NaCl + H₂CO₃
First, balance it.
Left: Na=2, C=1, O=3, H=1, Cl=1
Right: Na=1, Cl=1, H=2, C=1, O=3
Need 2 NaCl on right to match Na from left.
→ Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃
Now check:
Left: Na=2, C=1, O=3, H=2, Cl=2
Right: Na=2, Cl=2, H=2, C=1, O=3 → Balanced!
Type: Double replacement — ions swapped between Na₂CO₃ and HCl.
---
(ii) NH₄NO₂ → N₂ + H₂O
Balance:
Left: N=2, H=4, O=2
Right: N=2, H=2, O=1 → Need 2 H₂O
→ NH₄NO₂ → N₂ + 2H₂O
Check: Left: N=2, H=4, O=2; Right: N=2, H=4, O=2 → Balanced!
Type: Decomposition — one compound breaks into two simpler substances.
---
(iii) N₂ + O₂ → N₂O₅
Balance:
Left: N=2, O=2
Right: N=2, O=5 → Not balanced.
Find LCM of oxygen: 2 and 5 → 10
So try 5 O₂ on left → 10 O atoms
Then need 2 N₂O₅ on right → 4 N and 10 O
But left has only 2 N → so put 2 N₂ on left.
→ 2N₂ + 5O₂ → 2N₂O₅
Check: Left: N=4, O=10; Right: N=4, O=10 → Balanced!
Type: Synthesis — two elements combine to form one compound.
---
(iv) MgCO₃ → MgO + CO₂
Already balanced?
Left: Mg=1, C=1, O=3
Right: Mg=1, O=1+2=3, C=1 → Yes!
Type: Decomposition — one compound breaks into two.
---
(v) KBr + Cl₂ → KCl + Br₂
Balance:
Left: K=1, Br=1, Cl=2
Right: K=1, Cl=1, Br=2 → Need 2 KBr and 2 KCl
→ 2KBr + Cl₂ → 2KCl + Br₂
Check: Left: K=2, Br=2, Cl=2; Right: K=2, Cl=2, Br=2 → Balanced!
Type: Single replacement — Cl replaces Br in compound.
---
(vi) Zn + CuSO₄ → Cu + ZnSO₄
Already balanced?
Left: Zn=1, Cu=1, S=1, O=4
Right: Cu=1, Zn=1, S=1, O=4 → Yes!
Type: Single replacement — Zn replaces Cu.
---
(vii) P + O₂ → P₄O₆
Balance:
Left: P=1, O=2
Right: P=4, O=6
Need 4 P on left → 4P
Need 3 O₂ on left → 6 O atoms
→ 4P + 3O₂ → P₄O₆
Check: Left: P=4, O=6; Right: P=4, O=6 → Balanced!
Type: Synthesis — elements combine to form compound.
---
(viii) SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + NH₄Br
Balance:
Left: Sr=1, Br=2, N=2, H=8, C=1, O=3
Right: Sr=1, C=1, O=3, N=1, H=4, Br=1 → Need 2 NH₄Br
→ SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + 2NH₄Br
Check: Left: Sr=1, Br=2, N=2, H=8, C=1, O=3
Right: Sr=1, C=1, O=3, N=2, H=8, Br=2 → Balanced!
Type: Double replacement — ions swapped.
---
(ix) AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + NH₄NO₃
Balance:
Left: Ag=1, N=1+2=3? Wait — let's count carefully.
AgNO₃: Ag=1, N=1, O=3
(NH₄)₂CrO₄: N=2, H=8, Cr=1, O=4
Total left: Ag=1, N=3, H=8, Cr=1, O=7
Right: Ag₂CrO₄: Ag=2, Cr=1, O=4
NH₄NO₃: N=2, H=4, O=3 → Total right: Ag=2, Cr=1, O=7, N=2, H=4
Not balanced. Need 2 AgNO₃ on left → gives 2 Ag, 2 N, 6 O
Plus (NH₄)₂CrO₄ → adds 2 N, 8 H, 1 Cr, 4 O → total left: Ag=2, N=4, H=8, Cr=1, O=10
Right: Ag₂CrO₄ → Ag=2, Cr=1, O=4
Need 2 NH₄NO₃ → N=4, H=8, O=6 → total right: Ag=2, Cr=1, O=10, N=4, H=8 → Balanced!
→ 2AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + 2NH₄NO₃
Type: Double replacement.
---
(x) K + H₂O → KOH + H₂
Balance:
Left: K=1, H=2, O=1
Right: K=1, O=1, H=1+2=3? Wait — KOH has H=1, H₂ has H=2 → total H=3
Not balanced. Try 2K + 2H₂O → 2KOH + H₂
Left: K=2, H=4, O=2
Right: K=2, O=2, H=2 (from 2KOH) + 2 (from H₂) = 4 → Balanced!
→ 2K + 2H₂O → 2KOH + H₂
Type: Single replacement — K replaces H in water.
---
(xi) Al + Pb₂(NO₃)₂ → Al(NO₃)₃ + Pb
Balance:
Left: Al=1, Pb=2, N=2, O=6
Right: Al=1, N=3, O=9, Pb=1 → Not balanced.
Need to balance NO₃ groups. LCM of 2 and 3 is 6.
So put 3 Pb₂(NO₃)₂ → gives 6 Pb, 6 N, 18 O? Wait — better way:
Set coefficient for Al(NO₃)₃ as 2 → then need 6 NO₃ on left → so 3 Pb₂(NO₃)₂ → but that gives 6 Pb.
Then need 6 Pb on right.
And Al: if 2 Al(NO₃)₃, need 2 Al on left.
Try:
2Al + 3Pb₂(NO₃)₂ → 2Al(NO₃)₃ + 6Pb
Check:
Left: Al=2, Pb=6, N=6, O=18
Right: Al=2, N=6, O=18, Pb=6 → Balanced!
Type: Single replacement — Al replaces Pb.
---
(xii) Fe + O₂ → Fe₃O
Balance:
Left: Fe=1, O=2
Right: Fe=3, O=4
LCM of O: 4 → so 2 O₂ on left → 4 O
Need 3 Fe on left → 3Fe
→ 3Fe + 2O₂ → Fe₃O₄
Check: Left: Fe=3, O=4; Right: Fe=3, O=4 → Balanced!
Type: Synthesis — elements combine.
---
Final Answer:
(i) Balanced: Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃ ; Type: Double Replacement
(ii) Balanced: NH₄NO₂ → N₂ + 2H₂O ; Type: Decomposition
(iii) Balanced: 2N₂ + 5O₂ → 2N₂O₅ ; Type: Synthesis
(iv) Balanced: MgCO₃ → MgO + CO₂ ; Type: Decomposition
(v) Balanced: 2KBr + Cl₂ → 2KCl + Br₂ ; Type: Single Replacement
(vi) Balanced: Zn + CuSO₄ → Cu + ZnSO₄ ; Type: Single Replacement
(vii) Balanced: 4P + 3O₂ → P₄O₆ ; Type: Synthesis
(viii) Balanced: SrBr₂ + (NH₄)₂CO₃ → SrCO₃ + 2NH₄Br ; Type: Double Replacement
(ix) Balanced: 2AgNO₃ + (NH₄)₂CrO₄ → Ag₂CrO₄ + 2NH₄NO₃ ; Type: Double Replacement
(x) Balanced: 2K + 2H₂O → 2KOH + H₂ ; Type: Single Replacement
(xi) Balanced: 2Al + 3Pb₂(NO₃)₂ → 2Al(NO₃)₃ + 6Pb ; Type: Single Replacement
(xii) Balanced: 3Fe + 2O₂ → Fe₃O₄ ; Type: Synthesis
Parent Tip: Review the logic above to help your child master the concept of balancing chemical reactions worksheet.
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