CHEM Precipitation Reactions JavaLab | Jason Ritchie | - Free Printable

Since I can't access external websites or images directly, I’ll solve the Chemistry Lab #2 worksheet based on the information you provided. This lab involves predicting whether a double replacement (metathesis) reaction occurs when two ionic compounds are mixed in solution, identifying the precipitate, and determining the spectator ions.

We will analyze each pair of reactants using solubility rules and write net ionic equations to determine if a precipitate forms.

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🔬 Solubility Rules (Key Points)

1. Most nitrates (NO₃⁻) are soluble.
2. Most alkali metal (e.g., Na⁺, K⁺) salts are soluble.
3. Most ammonium (NH₄⁺) salts are soluble.
4. Most chlorides (Cl⁻) are soluble, except Ag⁺, Pb²⁺, Hg₂²⁺.
5. Most sulfides (S²⁻) are insoluble, except those with alkali metals and ammonium.
6. Most sulfates (SO₄²⁻) are soluble, except Ba²⁺, Sr²⁺, Pb²⁺, Ca²⁺.
7. Most hydroxides (OH⁻) and carbonates (CO₃²⁻) are insoluble, except those with alkali metals.

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Now let’s go through each reaction step-by-step.

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✔ Reaction 1: (6) Na₂S + (6) BaCl₂

Step 1: Write the balanced molecular equation
```
Na₂S(aq) + BaCl₂(aq) → BaS(s) + 2NaCl(aq)
```

Step 2: Check solubility
- BaS: Barium sulfide — insoluble (most sulfides are insoluble; BaS is an exception? Let's verify.)

Wait — BaS is actually soluble in water. But wait — no, this is a common misconception.

Actually, BaS is soluble in water. So no precipitate forms.

But let's double-check:

> Sulfides: Insoluble except for Group 1 (Na⁺, K⁺) and NH₄⁺.
> Ba²⁺ is not in Group 1 → BaS should be insoluble?

Wait — No, BaS is actually soluble.

According to standard solubility tables:
- BaS is soluble.
- BaSO₄ is insoluble, but BaS is soluble.

✔ So no precipitate forms.

→ No reaction.

Answer:
- Reaction: NO
- Precipitate: NONE
- Spectator ions: NONE (since no reaction)

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✔ Reaction 2: (6) Na₂S + (6) Ca(NO₃)₂

Molecular equation:
```
Na₂S(aq) + Ca(NO₃)₂(aq) → CaS(s) + 2NaNO₃(aq)
```

Check solubility:
- CaS: Calcium sulfide — insoluble? Actually, CaS is slightly soluble, but often considered insoluble in many contexts.

But in reality, CaS is moderately soluble, but it does form a precipitate in dilute solutions.

However, standard solubility rules say that sulfides of Ca²⁺ are insoluble.

So, CaS(s) forms.

Yes, reaction occurs.

Net ionic equation:
```
S²⁻(aq) + Ca²⁺(aq) → CaS(s)
```

Spectator ions: Na⁺ and NO₃⁻

Answer:
- Reaction: YES
- Precipitate: CaS
- Spectator ions: Na⁺, NO₃⁻

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✔ Reaction 3: (6) Na₂S + (6) KI

Molecular equation:
```
Na₂S(aq) + 2KI(aq) → K₂S(aq) + 2NaI(aq)
```

All products are soluble:
- K₂S: soluble (K⁺ salt)
- NaI: soluble (Na⁺ salt)

No precipitate.

No reaction

Answer:
- Reaction: NO
- Precipitate: NONE
- Spectator ions: NONE

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✔ Reaction 4: (6) Na₂S + (6) AgNO₃

Molecular equation:
```
Na₂S(aq) + 2AgNO₃(aq) → Ag₂S(s) + 2NaNO₃(aq)
```

Check solubility:
- Ag₂S: Silver sulfide — highly insoluble (one of the least soluble sulfides)

✔ Precipitate forms.

Net ionic:
```
S²⁻(aq) + 2Ag⁺(aq) → Ag₂S(s)
```

Spectator ions: Na⁺, NO₃⁻

Answer:
- Reaction: YES
- Precipitate: Ag₂S
- Spectator ions: Na⁺, NO₃⁻

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✔ Reaction 5: (6) Na₂S + (6) Pb(NO₃)₂

Molecular equation:
```
Na₂S(aq) + Pb(NO₃)₂(aq) → PbS(s) + 2NaNO₃(aq)
```

PbS: Lead(II) sulfide — very insoluble (black precipitate)

✔ Precipitate forms.

Net ionic:
```
S²⁻(aq) + Pb²⁺(aq) → PbS(s)
```

Spectator ions: Na⁺, NO₃⁻

Answer:
- Reaction: YES
- Precipitate: PbS
- Spectator ions: Na⁺, NO₃⁻

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✔ Reaction 6: (6) BaCl₂ + (6) KI

Molecular equation:
```
BaCl₂(aq) + 2KI(aq) → BaI₂(aq) + 2KCl(aq)
```

Check solubility:
- BaI₂: Soluble (all iodides are soluble except Ag⁺, Pb²⁺, Hg₂²⁺)
- KCl: Soluble

No precipitate.

No reaction

Answer:
- Reaction: NO
- Precipitate: NONE
- Spectator ions: NONE

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✔ Final Answer Table

| REACTANTS | Reaction | Precipitate Chem Formula | Spectator Ions |
|----------|---------|---------------------------|----------------|
| (6) Na₂S | (6) BaCl₂ | NO | NONE | NONE |
| (6) Na₂S | (6) Ca(NO₃)₂ | YES | CaS | Na⁺, NO₃⁻ |
| (6) Na₂S | (6) KI | NO | NONE | NONE |
| (6) Na₂S | (6) AgNO₃ | YES | Ag₂S | Na⁺, NO₃⁻ |
| (6) Na₂S | (6) Pb(NO₃)₂ | YES | PbS | Na⁺, NO₃⁻ |
| (6) BaCl₂ | (6) KI | NO | NONE | NONE |

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🔍 Summary Notes:

- Precipitates form only when an insoluble compound is produced.
- Spectator ions are those that do not participate in the reaction and remain in solution.
- Use solubility rules to predict outcomes.
- Common insoluble sulfides: Ag₂S, PbS, CuS, FeS, ZnS, etc.
- BaS is soluble, so no precipitate with BaCl₂ and Na₂S.

Let me know if you'd like a printable version or explanation of any specific reaction!