General Science PYQ – Matter, Atomic Structure, Acids, Bases and Salts – Part 2 (Q 32–62)
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One faraday deposits 1/3 mole of Al (Al3+ + 3e- gives Al), so 0.1 faraday deposits (0.1/3) x 27 = 0.9 g.
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General Science PYQ – Matter, Atomic Structure, Acids, Bases and Salts – Part 2 (Q 32–62) – 31 questions, subject: Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.
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1.
(i) o-Toluic acid
(ii) Benzoic acid
(iii) Salicylic acid
(iv) Picric acid
Group 1 2022
Which is the stronger acid than phenol due to the presence of three same electron-withdrawing groups?(i) o-Toluic acid
(ii) Benzoic acid
(iii) Salicylic acid
(iv) Picric acid
Correct Answer: D [(iv) only]
Explanation:
Picric acid (2,4,6-trinitrophenol) has three electron-withdrawing nitro groups that stabilise the phenoxide ion, making it much stronger than phenol.
2.
Junior Analyst 2023
Which of the following is the correct order of basicity of hydride compounds?Correct Answer: C [SbH₃ < AsH₃ < PH₃ < NH₃]
Explanation:
Down group 15 the central atom gets larger and the lone pair less available, so basicity decreases: SbH3 < AsH3 < PH3 < NH3.
3.
Mass Interviewer 2023
Which one of the following is not a Lewis acid?Correct Answer: B [NH₃]
Explanation:
A Lewis acid accepts an electron pair; BF3, AlCl3 and BH3 are electron-deficient, but NH3 has a lone pair to donate and is a Lewis base.
4.
CTS (Interview Posts) 2025
Which is not a Lewis acid among the following?Correct Answer: A [PH₃]
Explanation:
PH3 has a lone pair on phosphorus to donate, so it is a Lewis base, while BF3, AlCl3 and FeCl3 accept electron pairs and are Lewis acids.
5.
Bursar 2023
The conjugate bases of hydrochloric acid and acetic acid are ______ and ______.Correct Answer: B [Cl⁻ and CH₃COO⁻]
Explanation:
A conjugate base is what remains after an acid loses a proton, so HCl gives Cl- and CH3COOH gives CH3COO-.
6.
EO Group VII (HR&CE) 2022
A weak base has ______ conjugate acid and a weak acid has a ______ conjugate base.Correct Answer: A [Strong, strong]
Explanation:
A weak base has a strong conjugate acid and a weak acid has a strong conjugate base, since the strengths of an acid and its conjugate base are inversely related.
7.
(i) H₃O⁺ or H₂O
(ii) NH₄⁺ or NH₃
(iii) H₂S or HS⁻
(iv) H₂O or OH⁻
Group 2 2022
Choose the stronger acid in each of the following pairs:(i) H₃O⁺ or H₂O
(ii) NH₄⁺ or NH₃
(iii) H₂S or HS⁻
(iv) H₂O or OH⁻
Correct Answer: A [H₃O⁺, NH₄⁺, H₂S, H₂O]
Explanation:
The species with the extra proton is the stronger acid in each pair: H3O+ over H2O, NH4+ over NH3, H2S over HS- and H2O over OH-.
8.
Asst. Conservator of Forests 2023
Which of the following acts as an amphiprotic ion?Correct Answer: D [HS⁻]
Explanation:
An amphiprotic ion can both donate and accept a proton, and HS- can become S2- or H2S.
9.
Jailor 2023
If the pH of an aqueous solution at 25°C is 8, then its pOH is equal toCorrect Answer: D [6]
Explanation:
At 25 degrees C, pH + pOH = 14, so pOH = 14 - 8 = 6.
10.
Combined Engineering Subordinate Service 2023
If the pH of a solution is 4, its [OH⁻] ion concentration isCorrect Answer: D [1 × 10⁻¹⁰ M]
Explanation:
pH 4 means [H+] = 10^-4 M, and since [H+][OH-] = 10^-14, [OH-] = 1 x 10^-10 M.
11.
VAS AHGS 2020
Calculate the pH of a 5 × 10⁻³ M solution of barium hydroxide Ba(OH)₂ at 25°C (log₁₀5 = 0.6990) (Ba(OH)₂ is completely ionised).Correct Answer: D [12]
Explanation:
Ba(OH)2 gives two OH- per molecule so [OH-] = 10^-2 M, pOH = 2 and pH = 14 - 2 = 12.
12.
Group 4 2025
A 0.10 M weak acid is found to be dissociated to the extent of 1.20% at 25°C. Its dissociation constant isCorrect Answer: C [1.44 × 10⁻⁵]
Explanation:
For a weak acid Ka = C x alpha squared = 0.10 x (0.012)^2 = 1.44 x 10^-5.
13.
PTGS 2021
Buffer solutions are used toCorrect Answer: D [Maintain the pH value]
Explanation:
A buffer solution resists change in pH when small amounts of acid or base are added, thereby maintaining the pH.
14.
Field Surveyor 2022
Calculate the concentration of H₃O⁺ ion in a mixture of 0.08 M CH₃COOH and 0.06 M CH₃COONa at 298 K (Ka for acetic acid = 1.84 × 10⁻⁵).Correct Answer: A [2.4533 × 10⁻⁵ mol L⁻¹]
Explanation:
For an acidic buffer [H3O+] = Ka x [acid]/[salt] = 1.84 x 10^-5 x 0.08/0.06 = 2.4533 x 10^-5 mol per litre.
15.
Hostel Supdt. cum PTO 2024
In acid medium, phenolphthalein isCorrect Answer: D [Colourless]
Explanation:
Phenolphthalein is colourless in acidic solution and turns pink in basic solution.
16.
(a) Phenolphthalein in acidic medium – Colourless
(b) Phenolphthalein in basic medium – Yellow
(c) Methyl orange in acidic medium – Pink/Red
(d) Methyl orange in basic medium – Colourless
Fisheries Inspector / SI 2023
Choose the right matches among the following:(a) Phenolphthalein in acidic medium – Colourless
(b) Phenolphthalein in basic medium – Yellow
(c) Methyl orange in acidic medium – Pink/Red
(d) Methyl orange in basic medium – Colourless
Correct Answer: A [(a) and (c) are correct]
Explanation:
Phenolphthalein is colourless in acid and pink (not yellow) in base, and methyl orange is red/pink in acid, so (a) and (c) are the correct matches.
17.
1. Phenolphthalein – Colourless in acidic medium and pink in basic medium
2. Methyl orange – Pink in basic medium and yellow in acid medium
3. Red litmus paper – Turns blue in basic medium
4. Blue litmus paper – Turns red in basic medium
Group 4 2024
Choose the correct pairs:1. Phenolphthalein – Colourless in acidic medium and pink in basic medium
2. Methyl orange – Pink in basic medium and yellow in acid medium
3. Red litmus paper – Turns blue in basic medium
4. Blue litmus paper – Turns red in basic medium
Correct Answer: B [1 and 3 are correct]
Explanation:
Phenolphthalein is colourless in acid and pink in base, and red litmus turns blue in base, while methyl orange is yellow in base, so pairs 1 and 3 are correct.
18.
AD Social Welfare 2022
Bromothymol blue is used as an acid–base indicator. The colour of bromothymol blue in acidic medium isCorrect Answer: B [Yellow]
Explanation:
Bromothymol blue is yellow in acidic solution, green in neutral and blue in basic solution.
19.
Combined Engineering Services 2022
The main ingredient of an antacid, which is used to relieve acidity of the stomach, isCorrect Answer: B [Base]
Explanation:
Stomach acidity is due to excess HCl, and antacids contain mild bases that neutralise it.
20.
GSCE 2021
Magnesium hydroxide is used as a medicine for curingCorrect Answer: B [Stomach disorder]
Explanation:
Magnesium hydroxide (milk of magnesia) is a mild base that neutralises excess stomach acid and relieves indigestion.
21.
Group 3A 2023
The element that combines with other elements to make medicine for treating diarrheaCorrect Answer: A [Bismuth]
Explanation:
Bismuth compounds such as bismuth subsalicylate are used in medicines for diarrhoea and stomach upsets.
22.
AGGS 2021
Which one of the following aqueous solutions will have the highest pH value?Correct Answer: C [Na₂CO₃]
Explanation:
Na2CO3 is a salt of a strong base and a weak acid, so it hydrolyses to give a basic solution with the highest pH, whereas NaCl and KNO3 are neutral and ZnCl2 is acidic.
23.
PSY 2022
Which one of the following is a salt of weak acid and weak base?Correct Answer: D [Ammonium acetate]
Explanation:
Ammonium acetate is formed from a weak acid (acetic acid) and a weak base (ammonium hydroxide).
24.
ARGS 2020
Plaster of Paris isCorrect Answer: B [CaSO₄·½H₂O]
Explanation:
Plaster of Paris is calcium sulphate hemihydrate, CaSO4.1/2H2O, obtained by heating gypsum at about 373 K.
25.
(1) Washing soda – Sodium carbonate
(2) Baking soda – Calcium oxychloride
(3) Bleaching powder – Sodium bicarbonate
(4) Plaster of Paris – Calcium sulphate hemihydrate
CTS (ITI Posts) 2024
Choose the wrong pairs:(1) Washing soda – Sodium carbonate
(2) Baking soda – Calcium oxychloride
(3) Bleaching powder – Sodium bicarbonate
(4) Plaster of Paris – Calcium sulphate hemihydrate
Correct Answer: C [(2) and (3)]
Explanation:
Baking soda is sodium bicarbonate, not calcium oxychloride, and bleaching powder is calcium oxychloride, not sodium bicarbonate, so pairs (2) and (3) are wrong.
26.
(i) Green vitriol
(ii) White vitriol
(iii) Blue vitriol
(iv) Red vitriol
Asst. Professor (Psychology) 2023
Choose the one which is not a Heptahydrate.(i) Green vitriol
(ii) White vitriol
(iii) Blue vitriol
(iv) Red vitriol
Correct Answer: B [(iii) only]
Explanation:
Green, white and red vitriols (FeSO4, ZnSO4, CoSO4) are heptahydrates, but blue vitriol (CuSO4.5H2O) is a pentahydrate.
27.
(a) FeSO₄·7H₂O – 1. Textile industry
(b) Na₂CO₃·10H₂O – 2. Laboratory reagent
(c) CuSO₄·5H₂O – 3. Making of Mohr's salt
(d) ZnSO₄·7H₂O – 4. Fungicide
(e) BaCl₂·2H₂O – 5. Manufacture of glass
Group 1 2022
Match List I (Hydrated salt) with List II (Uses):(a) FeSO₄·7H₂O – 1. Textile industry
(b) Na₂CO₃·10H₂O – 2. Laboratory reagent
(c) CuSO₄·5H₂O – 3. Making of Mohr's salt
(d) ZnSO₄·7H₂O – 4. Fungicide
(e) BaCl₂·2H₂O – 5. Manufacture of glass
Correct Answer: C [3 5 4 1 2]
Explanation:
Matched as keyed: FeSO4.7H2O textile industry, Na2CO3.10H2O glass making, CuSO4.5H2O fungicide, ZnSO4.7H2O and BaCl2.2H2O as lab reagent, giving 3 5 4 1 2.
28.
Asst. Training Officer (Textile) 2023
Potash alum is a (double salt) mixture ofCorrect Answer: B [Potassium sulphate and aluminium sulphate]
Explanation:
Potash alum, K2SO4.Al2(SO4)3.24H2O, is a double salt of potassium sulphate and aluminium sulphate.
29.
AHGS 2021
The salt formed by the combination of the mixture of solutions of two simple salts and which lose identity of the salts from which it is formed.Correct Answer: A [Complex salt]
Explanation:
A complex salt forms when two simple salts combine and lose their separate identity, giving new complex ions in solution unlike a double salt.
30.
Group 1B/1C 2024
Which of the following compounds dissolves in water with the evolution of heat?Correct Answer: D [(A) and (B)]
Explanation:
Quick lime reacts with water releasing a lot of heat, and detergents also dissolve with heat evolution, so both (A) and (B) are correct.
31.
GSASO 2020
On passing 0.1 Faraday of electricity through AlCl₃, the amount of aluminium metal deposited on the cathode is (At. mass of Al = 27)Correct Answer: C [0.9 g]
Explanation:
One faraday deposits 1/3 mole of Al (Al3+ + 3e- gives Al), so 0.1 faraday deposits (0.1/3) x 27 = 0.9 g.
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