Acid, Base, and Salt classification worksheet for chemistry students.

Let's solve this step-by-step based on the Arrhenius definition of acids, bases, and salts.

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🔹 Arrhenius Definitions:

- Acid: A substance that dissociates in water to produce H⁺ ions (protons).
- Base: A substance that dissociates in water to produce OH⁻ ions.
- Salt: An ionic compound formed from the neutralization reaction between an acid and a base. It typically consists of a cation (from the base) and an anion (from the acid).

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## ✔ Problem 1: Classify using Arrhenius Definition

We'll classify each compound as acid, base, or salt.

| # | Compound | Classification | Reason |
|---|---------------|----------------|--------|
| 1 | HBr | Acid | Dissociates to H⁺ and Br⁻ → produces H⁺ |
| 2 | Mg(OH)₂ | Base | Contains OH⁻ groups → produces OH⁻ in water |
| 3 | HCl | Acid | Produces H⁺ and Cl⁻ |
| 4 | KNO₂ | Salt | Ionic compound from K⁺ and NO₂⁻; product of acid-base reaction |
| 5 | HI | Acid | Strong acid; produces H⁺ and I⁻ |
| 6 | Ba(OH)₂ | Base | Contains OH⁻ groups → produces OH⁻ |
| 7 | KCl | Salt | From HCl + KOH → K⁺ and Cl⁻ |
| 8 | H₃PO₄ | Acid | Phosphoric acid; releases H⁺ ions |
| 9 | HClO | Acid | Hypochlorous acid; releases H⁺ |
|10 | Al(OH)₃ | Base | Metal hydroxide; produces OH⁻ (though weak) |
|11 | KC₂H₃O₂ | Salt | Potassium acetate; from acetic acid and KOH |
|12 | NaCl | Salt | Sodium chloride; from HCl + NaOH |

✔ Answer Key for Problem 1:

1. HBr – Acid
2. Mg(OH)₂ – Base
3. HCl – Acid
4. KNO₂ – Salt
5. HI – Acid
6. Ba(OH)₂ – Base
7. KCl – Salt
8. H₃PO₄ – Acid
9. HClO – Acid
10. Al(OH)₃ – Base
11. KC₂H₃O₂ – Salt
12. NaCl – Salt

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## ✔ Problem 2: Classify as Acid/Base/Salt, then Strength & Salt Nature

Now we go beyond Arrhenius — we’ll classify as acid, base, or salt, and for acids/bases, state if strong or weak. For salts, determine if they are acidic, basic, or neutral based on their ions.

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🔸 Rules Recap:

#### Strong Acids (6 common):
- HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄

#### Strong Bases:
- Group 1 hydroxides: NaOH, KOH
- Group 2 hydroxides: Ca(OH)₂, Sr(OH)₂, Ba(OH)₂ (moderately soluble)

#### Weak Acids: All others (e.g., H₂S, HF, H₃PO₄, H₂CO₃, H₂Se, etc.)

#### Weak Bases: Most metal hydroxides except strong ones (e.g., Al(OH)₃, NH₄OH)

#### Salt pH Prediction:
- Neutral salt: From strong acid + strong base → e.g., NaCl
- Basic salt: From weak acid + strong base → e.g., Na₂CO₃
- Acidic salt: From strong acid + weak base → e.g., NH₄Cl

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| # | Compound | Type | Strength/Behavior | Salt Type (if applicable) |
|---|--------------|-------------|-------------------|----------------------------|
| 1 | HNO₃ | Acid | Strong | – |
| 2 | NaOH | Base | Strong | – |
| 3 | NaNO₃ | Salt | – | Neutral (Na⁺ from strong base, NO₃⁻ from strong acid) |
| 4 | KOH | Base | Strong | – |
| 5 | H₂S | Acid | Weak | – |
| 6 | Al(NO₃)₃ | Salt | – | Acidic (Al³⁺ hydrolyzes to form H⁺; NO₃⁻ is neutral) |
| 7 | H₂SO₄ | Acid | Strong (first proton) | – |
| 8 | CaCl₂ | Salt | – | Neutral (Ca²⁺ from strong base, Cl⁻ from strong acid) |
| 9 | H₃PO₄ | Acid | Weak | – |
|10 | H₂CO₃ | Acid | Weak | – |
|11 | NH₄OH | Base | Weak | – |
|12 | NH₄Cl | Salt | – | Acidic (NH₄⁺ is acidic, Cl⁻ is neutral) |
|13 | FeBr₃ | Salt | – | Acidic (Fe³⁺ hydrolyzes to give H⁺; Br⁻ neutral) |
|14 | HF | Acid | Weak | – |
|15 | H₂Se | Acid | Weak | – |
|16 | HMnO₄ | Acid | Strong (permanganic acid) | – |

> Note: HMnO₄ (permanganic acid) is a strong acid, though less commonly known.

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✔ Final Answers for Problem 2:

| # | Compound | Classification | Strength/Type |
|---|--------------|----------------|----------------|
| 1 | HNO₃ | Acid | Strong |
| 2 | NaOH | Base | Strong |
| 3 | NaNO₃ | Salt | Neutral |
| 4 | KOH | Base | Strong |
| 5 | H₂S | Acid | Weak |
| 6 | Al(NO₃)₃ | Salt | Acidic |
| 7 | H₂SO₄ | Acid | Strong |
| 8 | CaCl₂ | Salt | Neutral |
| 9 | H₃PO₄ | Acid | Weak |
|10 | H₂CO₃ | Acid | Weak |
|11 | NH₄OH | Base | Weak |
|12 | NH₄Cl | Salt | Acidic |
|13 | FeBr₃ | Salt | Acidic |
|14 | HF | Acid | Weak |
|15 | H₂Se | Acid | Weak |
|16 | HMnO₄ | Acid | Strong |

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📌 Summary Notes:

- Strong Acids: HNO₃, H₂SO₄, HCl, HBr, HI, HClO₄, HMnO₄
- Strong Bases: NaOH, KOH, Ba(OH)₂, Ca(OH)₂ (slightly soluble)
- Salt pH:
- Neutral: Both ions from strong acid/base (e.g., NaCl, CaCl₂)
- Acidic: Cation from weak base (e.g., NH₄⁺, Al³⁺, Fe³⁺)
- Basic: Anion from weak acid (e.g., CO₃²⁻, F⁻, CN⁻)

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✔ Final Answer Keys:

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Problem 1 Answers:

1. Acid
2. Base
3. Acid
4. Salt
5. Acid
6. Base
7. Salt
8. Acid
9. Acid
10. Base
11. Salt
12. Salt

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Problem 2 Answers:

| # | Compound | Type | Strength / Nature |
|---|--------------|--------|--------------------|
| 1 | HNO₃ | Acid | Strong |
| 2 | NaOH | Base | Strong |
| 3 | NaNO₃ | Salt | Neutral |
| 4 | KOH | Base | Strong |
| 5 | H₂S | Acid | Weak |
| 6 | Al(NO₃)₃ | Salt | Acidic |
| 7 | H₂SO₄ | Acid | Strong |
| 8 | CaCl₂ | Salt | Neutral |
| 9 | H₃PO₄ | Acid | Weak |
|10 | H₂CO₃ | Acid | Weak |
|11 | NH₄OH | Base | Weak |
|12 | NH₄Cl | Salt | Acidic |
|13 | FeBr₃ | Salt | Acidic |
|14 | HF | Acid | Weak |
|15 | H₂Se | Acid | Weak |
|16 | HMnO₄ | Acid | Strong |

Let me know if you'd like a printable version or explanations for any specific compound!