Chemistry worksheet 6.2 on word equations with completed examples.

Let’s go through each word equation and turn it into a balanced chemical equation. I’ll check each one step by step to make sure atoms balance on both sides.

---

a) Aluminium metal reacts with iron (III) oxide powder to produce aluminium oxide solid and iron metal.

Reactants: Al + Fe₂O₃
Products: Al₂O₃ + Fe

Unbalanced:
Al + Fe₂O₃ → Al₂O₃ + Fe

Balance O first: 3 O on left, 3 O on right — good for now.
Fe: 2 on left, 1 on right → put 2 in front of Fe on right.
Al: 1 on left, 2 on right → put 2 in front of Al on left.

Now:
2Al + Fe₂O₃ → Al₂O₃ + 2Fe ✔ Balanced.

But wait — the student wrote:
4Al + 3FeO → 2Al₂O₃ + 3Fe — that’s wrong because FeO is iron(II) oxide, not iron(III) oxide. Iron(III) oxide is Fe₂O₃.

So correct answer should be:
2Al + Fe₂O₃ → Al₂O₃ + 2Fe

Wait — let me double-check atom count:

Left: Al=2, Fe=2, O=3
Right: Al=2, O=3, Fe=2 → yes, balanced.

BUT — actually, this reaction is known as the thermite reaction, and it’s usually written with coefficients doubled to avoid fractions if needed, but here it’s already whole numbers.

Actually, standard form is:
2Al + Fe₂O₃ → Al₂O₃ + 2Fe

However, sometimes it's written as:
2Al + Fe₂O₃ → 2Fe + Al₂O₃ — same thing.

Student’s version used FeO — which is incorrect for iron(III) oxide.

So correction needed.

---

b) Aluminium hydroxide solution and calcium hydroxide solution produce a precipitate of aluminium hydroxide and total calcium sulphate.

Wait — “total calcium sulphate”? That doesn’t make sense. Probably typo — likely meant “calcium sulfate”.

Also, reactants are aluminum hydroxide and calcium hydroxide? But those are both bases — they don’t typically react to form a precipitate of aluminum hydroxide (which is already a reactant?).

This seems confused.

Looking at student’s answer:
Al(OH)₃ + Ca(OH)₂ → Al(OH)₃ + CaSO₄ — that can’t be right because there’s no sulfur in reactants!

Ah — probably the problem meant: aluminum sulfate and calcium hydroxide?

Because otherwise, you can’t get sulfate from nowhere.

Check original wording:
“Aluminium hydroxide solution and calcium hydroxide solution produce a precipitate of aluminium hydroxide and total calcium sulphate.”

That must be a mistake. Likely intended:
Aluminum sulfate + calcium hydroxide → aluminum hydroxide (ppt) + calcium sulfate

That makes sense — double displacement.

Assume that’s what was meant.

So:
Al₂(SO₄)₃ + Ca(OH)₂ → Al(OH)₃ ↓ + CaSO₄

Balance:

Left: Al=2, S=3, O from SO4=12, plus OH groups... better to write properly.

Standard balancing:

Al₂(SO₄)₃ + 3Ca(OH)₂ → 2Al(OH)₃ + 3CaSO₄

Check atoms:

Al: 2 = 2
S: 3 = 3
Ca: 3 = 3
O and H will balance too.

Yes.

Student wrote: Al(OH)₃ + Ca(OH)₂ → Al(OH)₃ + CaSO₄ — missing sulfate source, unbalanced, wrong.

So corrected:
Al₂(SO₄)₃ + 3Ca(OH)₂ → 2Al(OH)₃↓ + 3CaSO₄

---

c) Ammonia gas (NH₃) plus oxygen gas yields nitrogen monoxide gas plus water vapour.

Reactants: NH₃ + O₂
Products: NO + H₂O

Unbalanced:
NH₃ + O₂ → NO + H₂O

Balance N: 1 each side — ok.
H: 3 on left, 2 on right → LCM of 3 and 2 is 6 → so 2NH₃ and 3H₂O

Then:
2NH₃ + O₂ → NO + 3H₂O → now H: 6=6, N:2 vs 1 → need 2NO

So:
2NH₃ + O₂ → 2NO + 3H₂O

Now O: right has 2+3=5 O atoms → left has 2 from O₂ → need 5/2 O₂

Multiply all by 2:
4NH₃ + 5O₂ → 4NO + 6H₂O

Check:
N: 4=4
H: 12=12
O: 10=4+6=10 → balanced.

Student wrote: 4NH₃ + 5O₂ → 4NO + 6H₂O — CORRECT! ✔

---

d) Calcium hydroxide solution and carbon dioxide gas yields calcium carbonate and liquid water.

Reactants: Ca(OH)₂ + CO₂
Products: CaCO₃ + H₂O

Unbalanced:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Check atoms:

Ca: 1=1
C:1=1
O: 2+2=4 on left; 3+1=4 on right
H: 2=2 → already balanced!

So:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Student wrote: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O — CORRECT! ✔

(Note: student had "CaCO₃" correctly, though handwriting might look messy.)

---

e) Aqueous iron (III) chloride and sodium carbonate solution yields aqueous sodium chloride and a precipitate of iron (III) carbonate.

Reactants: FeCl₃ + Na₂CO₃
Products: NaCl + Fe₂(CO₃)₃ (since iron III is Fe³⁺, carbonate is CO₃²⁻ → formula is Fe₂(CO₃)₃)

Unbalanced:
FeCl₃ + Na₂CO₃ → NaCl + Fe₂(CO₃)₃

Balance Fe: 1 vs 2 → put 2 before FeCl₃
Cl: 6 on left → need 6 NaCl on right
Na: 6 on right → need 3 Na₂CO₃ on left (since each has 2 Na)
CO₃: 3 on left, 3 on right → good.

So:
2FeCl₃ + 3Na₂CO₃ → 6NaCl + Fe₂(CO₃)₃↓

Check:
Fe:2=2
Cl:6=6
Na:6=6
C:3=3
O:9=9 → balanced.

Student wrote: 2FeCl₃ + 3Na₂CO₃ → 6NaCl + Fe₂(CO₃)₃ — CORRECT! ✔

---

f) Solid zinc (II) oxide and carbon monoxide gas yield zinc metal and carbon dioxide gas.

Zinc(II) oxide = ZnO
Carbon monoxide = CO
Products: Zn + CO₂

Unbalanced:
ZnO + CO → Zn + CO₂

Check atoms:
Zn:1=1
O:1+1=2 on left; 2 on right → balanced!
C:1=1

So:
ZnO + CO → Zn + CO₂

Student wrote: ZnO + CO → Zn + CO₂ — CORRECT! ✔

---

g) Magnesium hydroxide solution and ammonium phosphate solution yields magnesium phosphate solid plus water and carbon dioxide gas.

Wait — carbon dioxide? Where does carbon come from? Reactants have Mg, O, H, N, P — no carbon!

Probably typo. Should be ammonia gas, not carbon dioxide.

Because when ammonium salts react with strong bases, they release ammonia gas.

Correct products: Mg₃(PO₄)₂ (solid), H₂O, and NH₃(g)

Reactants: Mg(OH)₂ + (NH₄)₃PO₄

Unbalanced:
Mg(OH)₂ + (NH₄)₃PO₄ → Mg₃(PO₄)₂ + H₂O + NH₃

Balance Mg: 3 on right → 3 Mg(OH)₂ on left
PO₄: 1 on left, 2 on right → 2 (NH₄)₃PO₄ on left

Now:
3Mg(OH)₂ + 2(NH₄)₃PO₄ → Mg₃(PO₄)₂ + H₂O + NH₃

Now N: left has 2×3=6 N → right needs 6 NH₃
H: left: 3×2=6 from OH, plus 2×12=24 from NH₄ → total H=30
Right: 6 NH₃ has 18 H, plus H₂O — let’s say x H₂O → 2x H
Total H right: 18 + 2x
Set equal: 18 + 2x = 30 → 2x=12 → x=6

O: left: 3×2=6 from OH, plus 2×4=8 from PO₄ → total O=14
Right: Mg₃(PO₄)₂ has 8 O, 6 H₂O has 6 O → total 14 → good.

So:
3Mg(OH)₂ + 2(NH₄)₃PO₄ → Mg₃(PO₄)₂↓ + 6H₂O + 6NH₃↑

Student wrote: Mg₃(PO₄)₂ + H₂O + CO₂ — included CO₂ which is wrong, and didn't balance.

So corrected version above.

---

h) Dilute nitric acid reacts with aqueous barium hydroxide and produces liquid water and barium nitrate plus (liquid) water.

Wait — says “produces liquid water and barium nitrate plus (liquid) water” — redundant.

Actually, neutralization:
HNO₃ + Ba(OH)₂ → Ba(NO₃)₂ + H₂O

Balance:

Ba:1=1
N:1 vs 2 → need 2 HNO₃
H: 2 from acid + 2 from base = 4 H → need 2 H₂O on right
O: will balance.

So:
2HNO₃ + Ba(OH)₂ → Ba(NO₃)₂ + 2H₂O

Student wrote: H₂SO₄ + Ba(OH)₂ → BaSO₄ + 2H₂O — that’s sulfuric acid, not nitric acid! Wrong acid.

Problem says “dilute nitric acid”, so must use HNO₃.

Correct:
2HNO₃(aq) + Ba(OH)₂(aq) → Ba(NO₃)₂(aq) + 2H₂O(l)

---

i) Aqueous sodium hydroxide and carbon dioxide gas yields sodium carbonate solution and liquid water.

Reactants: NaOH + CO₂
Products: Na₂CO₃ + H₂O

Unbalanced:
NaOH + CO₂ → Na₂CO₃ + H₂O

Na:1 vs 2 → 2NaOH
Then: 2NaOH + CO₂ → Na₂CO₃ + H₂O

Check H: 2=2
O: 2+2=4 left; 3+1=4 right
C:1=1 → balanced!

So:
2NaOH + CO₂ → Na₂CO₃ + H₂O

Student wrote: 2NaOH + CO₂ → Na₂CO₃ + H₂O — CORRECT! ✔

---

## Summary of Corrections Needed:

- a) Student used FeO instead of Fe₂O₃ → corrected to 2Al + Fe₂O₃ → Al₂O₃ + 2Fe
- b) Missing sulfate source → assumed aluminum sulfate + calcium hydroxide → Al₂(SO₄) + 3Ca(OH)₂ → 2Al(OH)₃↓ + 3CaSO₄
- g) Included CO₂ incorrectly → should be NH₃ → 3Mg(OH)₂ + 2(NH₄)₃PO₄ → Mg₃(PO₄)₂↓ + 6H₂O + 6NH₃↑
- h) Used H₂SO₄ instead of HNO₃ → corrected to 2HNO₃ + Ba(OH)₂ → Ba(NO₃)₂ + 2H₂O

Others were correct.

---

Final Answer:

a) 2Al + Fe₂O₃ → Al₂O₃ + 2Fe
b) Al₂(SO₄)₃ + 3Ca(OH)₂ → 2Al(OH)₃↓ + 3CaSO₄
c) 4NH₃ + 5O₂ → 4NO + 6H₂O
d) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
e) 2FeCl₃ + 3Na₂CO₃ → 6NaCl + Fe₂(CO₃)₃↓
f) ZnO + CO → Zn + CO₂
g) 3Mg(OH)₂ + 2(NH₄)₃PO₄ → Mg(PO₄)₂↓ + 6H₂O + 6NH₃↑
h) 2HNO₃ + Ba(OH)₂ → Ba(NO₃)₂ + 2H₂O
i) 2NaOH + CO₂ → Na₂CO₃ + H₂O