BPSC CCE Prelims
Acids, Bases and Salts Previous Year Questions (PYQs)
Practice solved questions for Acids, Bases and Salts with detailed step-by-step solutions, key insights, and trend analysis for BPSC CCE PRELIMS.
Solved Previous Year Questions
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Sour taste of vinegar is due to
Detailed Explanation:
The sour taste of vinegar is due to acetic acid (CH₃COOH), which is produced by fermentation of ethanol.
Tartaric acid is found in tamarind and grapes, lactic acid in sour milk and curd, and citric acid in citrus fruits — none of these is the acid in vinegar.
pH value of 0.1N HCl solution is approximately:
Detailed Explanation:
HCl is a strong acid that dissociates completely: HCl → H⁺ + Cl⁻. For a monoprotic acid, 0.1N = 0.1M, so [H⁺] = 0.1 M.
pH = -log[H⁺] = -log(0.1) = -(-1) = 1.0. Options with pH 10 or 11 indicate basic solutions, not acids. pH 2.0 would require [H⁺] = 0.01 M, which is ten times more dilute.
Some metal oxides react with acid as well as a base to produce salt and water. They are known as amphoteric oxides. Examples of amphoteric oxides are
Detailed Explanation:
Amphoteric oxides react with both acids and bases to form salt and water.
✅ Al₂O₃ (Aluminium oxide) reacts with HCl to give AlCl₃ + H₂O and with NaOH to give NaAlO₂ + H₂O.
✅ ZnO (Zinc oxide) reacts with H₂SO₄ to give ZnSO₄ + H₂O and with NaOH to give Na₂ZnO₂ + H₂O.
❌ CuO (Copper oxide) is a basic oxide that reacts only with acids, not with bases.
Therefore, Option 2 (Al₂O₃ and ZnO) is the correct answer.
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Acids react with metal carbonates to liberate ______ gas.
Detailed Explanation:
When acids react with metal carbonates, the general reaction is: Acid + Metal Carbonate → Salt + Water + CO₂.
For example, HCl + CaCO₃ → CaCl₂ + H₂O + CO₂, producing carbon dioxide gas (CO₂) which is observed as effervescence (bubbles).
Which acid is described as HOOCCOOH?
Detailed Explanation:
HOOCCOOH is the chemical formula for Oxalic acid, a dicarboxylic acid with two carboxyl groups (-COOH).
Carbonic acid is H₂CO₃, Acetic acid is CH₃COOH, making Option 2 the only correct answer.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. Which of them will turn red litmus to blue?
Detailed Explanation:
Red litmus paper turns blue only in the presence of a basic (alkaline) solution.
Distilled water is neutral (pH 7) and does not change litmus colour; acidic solutions turn blue litmus red, not the reverse; only bases have the chemical property to convert red litmus to blue.
Why does dry HCI gas not change the colour of dry litmus paper?
Detailed Explanation:
Dry HCl gas does not ionize to produce H₃O⁺ (hydronium) ions because ionization requires the presence of water molecules.
Litmus paper changes colour only when H₃O⁺ ions are present in solution; dry HCl remains molecular (HCl) and cannot act as an acid without water to donate protons to.
Which among the following solutions has pH value more than 7?
Detailed Explanation:
pH scale measures acidity and basicity: pH < 7 indicates acidic, pH = 7 is neutral, and pH > 7 indicates basic (alkaline) solutions.
Basic solutions have excess hydroxide ions (OH⁻), resulting in pH values greater than 7. Examples include sodium hydroxide, potassium hydroxide, and ammonia solutions.
Therefore, only basic solutions have pH > 7, making Option 2 the correct answer.
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