Chemistry 110 Worksheet: Reactions in Aqueous Solutions (Acid-Base & Precipitation Reactions)

Let's solve each of these chemical reactions step by step. We'll:

1. Predict the products using double displacement (metathesis) or acid-base reaction rules.
2. Balance the equation.
3. Determine if any product is a precipitate using solubility rules.

We will use general solubility rules for ionic compounds in water:

Solubility Rules (Key ones):

- All nitrates (NO₃⁻) are soluble.
- All alkali metal (e.g., Na⁺, K⁺, Li⁺) salts are soluble.
- Most acetates (CH₃COO⁻) and ammonium (NH₄⁺) salts are soluble.
- Most chlorides (Cl⁻) are soluble, except Ag⁺, Pb²⁺, Hg₂²⁺.
- Most sulfates (SO₄²⁻) are soluble, except Ba²⁺, Sr²⁺, Pb²⁺, Ca²⁺ (CaSO₄ slightly soluble).
- Most carbonates (CO₃²⁻), phosphates (PO₄³⁻), sulfides (S²⁻), hydroxides (OH⁻) are insoluble, except those with alkali metals and NH₄⁺.
- Hydroxides of Ca²⁺, Sr²⁺, Ba²⁺ are slightly soluble.

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Now, let’s go through each reaction.

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1. NaBr(aq) + AgNO₃(aq) →

Products: NaNO₃ and AgBr
Balanced:
NaBr(aq) + AgNO₃(aq) → NaNO₃(aq) + AgBr(s)

Solubility check:
- NaNO₃: soluble (all nitrates soluble) ✔
- AgBr: insoluble (Ag⁺ salts are insoluble, especially Br⁻) ✘ → precipitate

✔ Answer:
NaBr(aq) + AgNO₃(aq) → NaNO₃(aq) + AgBr(s)↓

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2. K₂S(aq) + ZnBr₂(aq) →

Products: KBr and ZnS
Balanced:
K₂S(aq) + ZnBr₂(aq) → 2KBr(aq) + ZnS(s)

Solubility check:
- KBr: soluble (alkali metal salt) ✔
- ZnS: insoluble (most sulfides are insoluble, except alkali metals) ✘ → precipitate

✔ Answer:
K₂S(aq) + ZnBr₂(aq) → 2KBr(aq) + ZnS(s)↓

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3. Li₃PO₄(aq) + AlCl₃(aq) →

Products: LiCl and AlPO₄
Balanced:
Li₃PO₄(aq) + AlCl₃(aq) → 3LiCl(aq) + AlPO₄(s)

Solubility check:
- LiCl: soluble ✔
- AlPO₄: insoluble (phosphates are generally insoluble except with alkali metals) ✘ → precipitate

✔ Answer:
Li₃PO₄(aq) + AlCl₃(aq) → 3LiCl(aq) + AlPO₄(s)↓

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4. HI(aq) + LiOH(aq) →

This is an acid-base neutralization:
HI + LiOH → LiI + H₂O

Balanced:
HI(aq) + LiOH(aq) → LiI(aq) + H₂O(l)

Solubility check:
- LiI: soluble ✔
- H₂O: liquid, not a precipitate

✔ Answer:
HI(aq) + LiOH(aq) → LiI(aq) + H₂O(l)
(No precipitate)

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5. HBr(aq) + Ba(OH)₂(aq) →

Acid-base reaction:
HBr + Ba(OH)₂ → BaBr₂ + H₂O

Balanced:
2HBr(aq) + Ba(OH)₂(aq) → BaBr₂(aq) + 2H₂O(l)

Solubility check:
- BaBr₂: soluble (most bromides are soluble; Ba²⁺ bromide is soluble) ✔
- H₂O: liquid

✔ Answer:
2HBr(aq) + Ba(OH)₂(aq) → BaBr₂(aq) + 2H₂O(l)
(No precipitate)

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6. (NH₄)₂CO₃(aq) + MgCl₂(aq) →

Double displacement:
(NH₄)₂CO₃ + MgCl₂ → 2NH₄Cl + MgCO₃

Balanced:
(NH₄)₂CO₃(aq) + MgCl₂(aq) → 2NH₄Cl(aq) + MgCO₃(s)

Solubility check:
- NH₄Cl: soluble ✔
- MgCO₃: insoluble (carbonates are generally insoluble) ✘ → precipitate

✔ Answer:
(NH₄)₂CO₃(aq) + MgCl₂(aq) → 2NH₄Cl(aq) + MgCO₃(s)↓

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7. CuCl₂(aq) + KNO₃(aq) →

Products: Cu(NO₃)₂ and KCl
All possible products are soluble:
- Cu(NO₃)₂: soluble (nitrates always soluble)
- KCl: soluble

So no precipitate forms.

Balanced:
CuCl₂(aq) + 2KNO₃(aq) → Cu(NO₃)₂(aq) + 2KCl(aq)

✔ Answer:
CuCl₂(aq) + 2KNO₃(aq) → Cu(NO₃)₂(aq) + 2KCl(aq)
(No precipitate)

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8. MgBr₂(aq) + Pb(NO₃)₂(aq) →

Products: Mg(NO₃)₂ and PbBr₂

Balanced:
MgBr₂(aq) + Pb(NO₃)₂(aq) → Mg(NO₃)₂(aq) + PbBr₂(s)

Solubility check:
- Mg(NO₃)₂: soluble ✔
- PbBr₂: insoluble (Pb²⁺ salts are often insoluble; bromides of Pb²⁺ are insoluble) ✘ → precipitate

✔ Answer:
MgBr₂(aq) + Pb(NO₃)₂(aq) → Mg(NO₃)₂(aq) + PbBr₂(s)↓

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9. H₂SO₄(aq) + KOH(aq) →

Acid-base reaction:
H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O

Balanced:
H₂SO₄(aq) + 2KOH(aq) → K₂SO₄(aq) + 2H₂O(l)

Solubility check:
- K₂SO₄: soluble ✔
- H₂O: liquid

✔ Answer:
H₂SO₄(aq) + 2KOH(aq) → K₂SO₄(aq) + 2H₂O(l)
(No precipitate)

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10. Na₃PO₄(aq) + MgCl₂(aq) →

Products: NaCl and Mg₃(PO₄)₂

Balanced:
2Na₃PO₄(aq) + 3MgCl₂(aq) → 6NaCl(aq) + Mg₃(PO₄)₂(s)

Solubility check:
- NaCl: soluble ✔
- Mg₃(PO₄)₂: insoluble (phosphates are insoluble except with alkali metals) ✘ → precipitate

✔ Answer:
2Na₃PO₄(aq) + 3MgCl₂(aq) → 6NaCl(aq) + Mg₃(PO₄)₂(s)↓

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11. HCl(aq) + KOH(aq) →

Acid-base reaction:
HCl + KOH → KCl + H₂O

Balanced:
HCl(aq) + KOH(aq) → KCl(aq) + H₂O(l)

Solubility check:
- KCl: soluble ✔
- H₂O: liquid

✔ Answer:
HCl(aq) + KOH(aq) → KCl(aq) + H₂O(l)
(No precipitate)

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12. Pb(NO₃)₂(aq) + AlCl₃(aq) →

Products: PbCl₂ and Al(NO₃)₃

Balanced:
3Pb(NO₃)₂(aq) + 2AlCl₃(aq) → 3PbCl₂(s) + 2Al(NO₃)₃(aq)

Solubility check:
- Al(NO₃)₃: soluble ✔
- PbCl₂: insoluble (Pb²⁺ chloride is insoluble) ✘ → precipitate

✔ Answer:
3Pb(NO₃)₂(aq) + 2AlCl₃(aq) → 3PbCl₂(s)↓ + 2Al(NO₃)₃(aq)

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13. H₃PO₄(aq) + NaOH(aq) →

Acid-base reaction:
H₃PO₄ is triprotic, so it can react in steps, but we write the complete neutralization:

H₃PO₄ + 3NaOH → Na₃PO₄ + 3H₂O

Balanced:
H₃PO₄(aq) + 3NaOH(aq) → Na₃PO₄(aq) + 3H₂O(l)

Solubility check:
- Na₃PO₄: soluble ✔
- H₂O: liquid

✔ Answer:
H₃PO₄(aq) + 3NaOH(aq) → Na₃PO₄(aq) + 3H₂O(l)
(No precipitate)

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✔ Final Answers Summary:

| Reaction | Balanced Equation | Precipitate? |
|--------|-------------------|-------------|
| 1 | NaBr(aq) + AgNO₃(aq) → NaNO₃(aq) + AgBr(s)↓ | AgBr(s) |
| 2 | K₂S(aq) + ZnBr₂(aq) → 2KBr(aq) + ZnS(s)↓ | ZnS(s) |
| 3 | Li₃PO₄(aq) + AlCl₃(aq) → 3LiCl(aq) + AlPO₄(s)↓ | AlPO₄(s) |
| 4 | HI(aq) + LiOH(aq) → LiI(aq) + H₂O(l) | No |
| 5 | 2HBr(aq) + Ba(OH)₂(aq) → BaBr₂(aq) + 2H₂O(l) | No |
| 6 | (NH₄)₂CO₃(aq) + MgCl₂(aq) → 2NH₄Cl(aq) + MgCO₃(s)↓ | MgCO₃(s) |
| 7 | CuCl₂(aq) + 2KNO₃(aq) → Cu(NO₃)₂(aq) + 2KCl(aq) | No |
| 8 | MgBr₂(aq) + Pb(NO₃)₂(aq) → Mg(NO₃)₂(aq) + PbBr₂(s)↓ | PbBr₂(s) |
| 9 | H₂SO₄(aq) + 2KOH(aq) → K₂SO₄(aq) + 2H₂O(l) | No |
| 10 | 2Na₃PO₄(aq) + 3MgCl₂(aq) → 6NaCl(aq) + Mg₃(PO₄)₂(s)↓ | Mg₃(PO₄)₂(s) |
| 11 | HCl(aq) + KOH(aq) → KCl(aq) + H₂O(l) | No |
| 12 | 3Pb(NO₃)₂(aq) + 2AlCl₃(aq) → 3PbCl₂(s)↓ + 2Al(NO₃)₃(aq) | PbCl₂(s) |
| 13 | H₃PO₄(aq) + 3NaOH(aq) → Na₃PO₄(aq) + 3H₂O(l) | No |

> ✔ All equations are balanced and precipitates marked accordingly.

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