Chemistry quiz focusing on acids, bases, and salts, featuring multiple-choice questions about common substances, indicators, and chemical properties.

Let's go through each question one by one and solve them with explanations.

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1. Which one of the following is acidic?
(a) Lemon juice
(b) Tomatoes
(c) Milk
(d) All

✔ Answer: (d) All

Explanation:
- Lemon juice contains citric acid → acidic
- Tomatoes contain oxalic and citric acids → acidic
- Milk contains lactic acid → slightly acidic (pH around 6.5–6.7)
So, all are acidic in nature.

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2. Which one of the following will turn red litmus blue?
(a) Vinegar
(b) Baking soda solution
(c) Lemon juice
(d) Soft drinks

✔ Answer: (b) Baking soda solution

Explanation:
Red litmus turns blue in basic solutions.
- Vinegar (acetic acid), lemon juice, soft drinks → acidic → no change or turn blue to red
- Baking soda (NaHCO₃) solution is basic → turns red litmus blue

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3. Which one of the following will turn blue litmus red?
(a) Vinegar
(b) Lime water
(c) Baking soda solution
(d) Washing soda solution

✔ Answer: (a) Vinegar

Explanation:
Blue litmus turns red in acidic solutions.
- Vinegar (acetic acid) → acidic → turns blue litmus red
- Lime water (Ca(OH)₂), baking soda, washing soda → basic → no change or turn red to blue

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4. Methyl orange is
(a) Pink in acidic medium, yellow in basic medium
(b) Yellow in acidic medium, pink in basic medium
(c) Colourless in acidic medium, pink in basic medium
(d) Pink in acidic medium, colourless in basic medium

✔ Answer: (a) Pink in acidic medium, yellow in basic medium

Explanation:
Methyl orange is a pH indicator:
- Acidic pH (<3.1): Red/Pink
- Basic pH (>4.4): Yellow
So, it changes from pink (acidic) to yellow (basic)

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5. Lime water is
(a) CaO
(b) Ca(OH)₂
(c) CaCO₃
(d) CaCl₂

✔ Answer: (b) Ca(OH)₂

Explanation:
Lime water is a saturated solution of calcium hydroxide, Ca(OH)₂.
- CaO = quicklime
- CaCO₃ = limestone
- CaCl₂ = calcium chloride

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6. The nature of calcium phosphate present in tooth enamel is
(a) Basic
(b) Amphoteric
(c) Acidic
(d) Neutral

✔ Answer: (a) Basic

Explanation:
Calcium phosphate (Ca₃(PO₄)₂) in tooth enamel is basic in nature because it is a salt of a strong base (Ca(OH)₂) and weak acid (H₃PO₄). It resists acid attack but can be dissolved in acidic conditions (e.g., by bacterial acids causing cavities).

> Note: Some may argue it’s neutral or amphoteric, but in biological context, it's considered basic due to its resistance to acid and origin.

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7. Which of the following salts has no water of crystallization?
(a) Blue vitriol
(b) Washing soda
(c) Baking soda
(d) Gypsum

✔ Answer: (c) Baking soda

Explanation:
- Blue vitriol = CuSO₄·5H₂O → has water of crystallization
- Washing soda = Na₂CO₃·10H₂O → has water
- Baking soda = NaHCO₃ → no water of crystallization
- Gypsum = CaSO₄·2H₂O → has water

So, only baking soda is anhydrous.

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8. The function of quick lime in soda lime mixture is to
(a) Absorb moisture present in soda lime
(b) Increase the efficiency of soda lime
(c) Increase the pH of soda lime
(d) Take part in reaction with NaOH

✔ Answer: (a) Absorb moisture present in soda lime

Explanation:
Soda lime is a mixture of NaOH and CaO (quick lime).
Quick lime (CaO) acts as a desiccant — it absorbs moisture and prevents NaOH from deteriorating. This helps maintain the effectiveness of the mixture for absorbing CO₂.

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9. The pH of a solution of HCl is 4. This shows that the molarity of the solution is
(a) 4.0M
(b) 0.4M
(c) 0.0001M
(d) 0.001M

✔ Answer: (d) 0.001M

Explanation:
For strong acids like HCl:
pH = -log[H⁺]
So, [H⁺] = 10^(-pH) = 10⁻⁴ = 0.0001 M? Wait...

Wait: 10⁻⁴ = 0.0001 M → but option (c) is 0.0001M and (d) is 0.001M

But let's check:

- pH = 4 → [H⁺] = 10⁻⁴ = 0.0001 M → so answer should be (c)?

Wait! Let's double-check:

10⁻⁴ = 0.0001 → correct

But options:
(c) 0.0001M
(d) 0.001M = 10⁻³

So correct answer is (c) 0.0001M

Wait — this seems conflicting.

But let's see:

- pH = 4 → [H⁺] = 10⁻⁴ = 0.0001 M → matches (c)

So why is (d) listed?

Possibly typo? But based on calculation:

✔ Answer: (c) 0.0001M

> Correction: If pH = 4, then [H⁺] = 10⁻⁴ = 0.0001 M → So (c) is correct.

But wait: Is there any mistake?

No. So (c) 0.0001M is correct.

But let me confirm:
10⁻⁴ = 0.0001 → yes
10⁻³ = 0.001 → (d)

So answer is (c)

✔ Correct Answer: (c) 0.0001M

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10. The difference of molecules of water in gypsum and PoP is
(a) 5/2
(b) 2b
(c) 3/2
(d) ½

Note: "PoP" = Plaster of Paris

- Gypsum = CaSO₄·2H₂O
- Plaster of Paris = CaSO₄·½H₂O

So, difference in water molecules = 2 – ½ = 1.5 = 3/2

✔ Answer: (c) 3/2

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11. Which of the following does not form an acidic salt?
(a) Phosphoric acid
(b) Carbonic acid
(c) Hydrochloric acid
(d) Sulphuric acid

✔ Answer: (c) Hydrochloric acid

Explanation:
An acidic salt is formed when only some of the H⁺ ions of a polyprotic acid are replaced.

- Phosphoric acid (H₃PO₄) → forms H₂PO₄⁻, HPO₄²⁻ → acidic salts
- Carbonic acid (H₂CO₃) → forms HCO₃⁻ → acidic salt
- Sulphuric acid (H₂SO₄) → forms HSO₄⁻ → acidic salt
- Hydrochloric acid (HCl) → monoprotic → only one H⁺ → forms normal salt (NaCl), not acidic salt

So, HCl cannot form acidic salt because it has only one replaceable hydrogen.

✔ Answer: (c) Hydrochloric acid

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12. The chemical formula of caustic potash is
(a) NaOH
(b) Ca(OH)₂
(c) NH₄OH
(d) KOH

✔ Answer: (d) KOH

Explanation:
- Caustic potash = Potassium hydroxide = KOH
- NaOH = caustic soda
- Ca(OH)₂ = slaked lime
- NH₄OH = ammonium hydroxide

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✔ Final Answers Summary:

| Q | Answer |
|---|--------|
| 1 | (d) All |
| 2 | (b) Baking soda solution |
| 3 | (a) Vinegar |
| 4 | (a) Pink in acidic, yellow in basic |
| 5 | (b) Ca(OH)₂ |
| 6 | (a) Basic |
| 7 | (c) Baking soda |
| 8 | (a) Absorb moisture |
| 9 | (c) 0.0001M |
|10 | (c) 3/2 |
|11 | (c) Hydrochloric acid |
|12 | (d) KOH |

Let me know if you want these explained further!