General Science PYQ – Matter, Atomic Structure, Acids, Bases and Salts – Part 1 (Q 1–31)

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General Science PYQ – Matter, Atomic Structure, Acids, Bases and Salts – Part 1 (Q 1–31) – 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.  
Group 1 2021
The common table salt is

Correct Answer: A [Compound]

Explanation:

Common salt (NaCl) is a compound in which sodium and chlorine are chemically combined in a fixed ratio.

2.  
Road Inspector 2023
Cane sugar is made up of three elements ______, ______ and ______.

Correct Answer: B [Carbon, hydrogen and oxygen]

Explanation:

Cane sugar (sucrose, C12H22O11) is made of carbon, hydrogen and oxygen, like all carbohydrates.

3.  
Combined Accounts Service 2024
Gas law (pressure–volume relation) was given by

Correct Answer: D [Robert Boyle]

Explanation:

Boyle's law, stating that at constant temperature the volume of a gas is inversely proportional to its pressure, was given by Robert Boyle in 1662.

4.  
District Child Protection Officer 2022
The charge of an atom is

Correct Answer: B [neutral]

Explanation:

An atom has equal numbers of protons and electrons, so it is electrically neutral.

5.  
Group 1 2021
What are isotones?

Correct Answer: B [Atoms having same number of neutrons but different number of protons]

Explanation:

Isotones are atoms with the same number of neutrons but different numbers of protons, such as carbon-14 and nitrogen-15.

6.  
VAS AHGS 2020
Who proposed the law of octaves while arranging the elements in the periodic table?

Correct Answer: B [Newlands]

Explanation:

John Newlands noticed that every eighth element resembled the first when arranged by atomic mass and called this the law of octaves.

7.  
Fisheries Inspector / SI 2023
"The atomic mass of the middle element is nearly the same as the average of the atomic masses of the other two elements." This is

Correct Answer: C [Döbereiner's law of triads]

Explanation:

Dobereiner's law of triads states that in a triad of similar elements the atomic mass of the middle element is about the average of the other two.

8.  
Executive Officer Gr. III (HR&CE) 2022
______ stated that the properties of elements are a periodic function of their atomic numbers.

Correct Answer: D [Moseley]

Explanation:

Henry Moseley showed from X-ray studies that atomic number, not atomic mass, is fundamental, giving the modern periodic law.

9.  
AD Town & Country Planning 2022
d-block elements are called

Correct Answer: B [Transition metals]

Explanation:

The d-block elements, lying between the s- and p-blocks, show transitional properties and are called transition metals.

10.  
Combined Engineering Subordinate Service 2023
The only block that contains all three types of elements (metals, non-metals and metalloids) in the periodic table is

Correct Answer: B [p-block]

Explanation:

The p-block alone contains metals (Al, Sn, Pb), non-metals (C, N, O, halogens) and metalloids (B, Si, Ge, As).

11.  
GSHA 2021
Which pair of elements has the similar chemical properties? (Z means atomic number)

Correct Answer: B [Z = 11; Z = 19]

Explanation:

Z = 11 (sodium) and Z = 19 (potassium) are in the same group (alkali metals) with similar outer electron configuration, so they have similar chemical properties.

12.  
VCGS 2022 · Asst. Training Officer (Textile) 2023
The only non-metal which is a liquid at room temperature is

Correct Answer: D [Bromine]

Explanation:

Bromine is the only non-metal that is liquid at room temperature, while mercury is the liquid metal.

13.  
Jailor 2023
Which of the following is/are not an allotrope of carbon?
(i) Diamond
(ii) Carborundum
(iii) Graphite
(iv) Fullerene

Correct Answer: C [(ii) alone]

Explanation:

Diamond, graphite and fullerene are allotropes of carbon, but carborundum (SiC) is a compound of silicon and carbon, so (ii) alone is not an allotrope.

14.  
Junior Rehabilitation Officer 2023
A compound as hard as diamond is

Correct Answer: A [Silicon carbide]

Explanation:

Silicon carbide (carborundum, SiC) is nearly as hard as diamond and is used as an abrasive.

15.  
Junior Analyst 2023
Assertion [A]: Diamond is used for cutting glass.
Reason [R]: Diamond has a high refractive index.

Correct Answer: B [Both [A] and [R] are true but [R] is not the correct explanation of [A]]

Explanation:

Diamond cuts glass because it is the hardest natural substance; its high refractive index is true but does not explain the cutting, so R is not the correct explanation.

16.  
Asst. Jailor 2023
The gas which turns lime water milky is

Correct Answer: C [Carbon dioxide]

Explanation:

Carbon dioxide reacts with lime water to form insoluble calcium carbonate, turning it milky.

17.  
ARGS 2020
Marble contains

Correct Answer: B [CaCO₃]

Explanation:

Marble is a form of calcium carbonate (CaCO3), like limestone and chalk.

18.  
GSASO 2020 · CSSS 2023
SiO₂ is

Correct Answer: A [an acidic oxide]

Explanation:

SiO2 is a non-metal oxide that reacts with bases to give silicates, so it is an acidic oxide.

19.  
VCGS 2022
Superoxides contain

Correct Answer: D [O₂⁻ ion]

Explanation:

Superoxides such as KO2 contain the O2- ion, whereas peroxides contain O2 2- and normal oxides contain O 2-.

20.  
Road Inspector 2023
Aluminium reacts with sodium hydroxide to give

Correct Answer: D [Sodium meta-aluminate + hydrogen]

Explanation:

Aluminium reacts with sodium hydroxide to give sodium meta-aluminate and hydrogen gas: 2Al + 2NaOH + 2H2O gives 2NaAlO2 + 3H2.

21.  
Asst. Public Prosecutor Gr. II 2026
When an iron nail is rusted, iron oxide is formed

Correct Answer: B [with increase in the weight of the nail]

Explanation:

Rusting adds oxygen and water to iron forming hydrated iron oxide, so the nail's weight increases.

22.  
GSASO 2020
Which acid is not kept in glass bottles?

Correct Answer: A [HF]

Explanation:

Hydrofluoric acid reacts with silica in glass (SiO2 + 4HF gives SiF4 + 2H2O) and corrodes it, so it is not kept in glass bottles.

23.  
CTS (Interview Posts) 2026
Assertion [A]: Aqueous solution of hydrofluoric acid is a weak acid.
Reason [R]: The dissociation energy of the H–F bond in the HF molecule is high.

Correct Answer: D [Both [A] and [R] are true, and [R] is the correct explanation of [A]]

Explanation:

The H-F bond has very high dissociation energy, so HF ionises poorly in water and is a weak acid, and the reason explains the assertion.

24.  
Executive Officer Gr. IV (HR&CE) 2022
A 3:1 ratio of concentrated acids of ______ is used for cleaning and refining gold.

Correct Answer: A [HCl and HNO₃]

Explanation:

Aqua regia, a 3:1 mixture of concentrated hydrochloric and nitric acids, dissolves gold and platinum and is used to clean and refine gold.

25.  
Special Competitive Exam 2025
Choose the right pairs:
1. Organic acids – HCOOH, CH₃COOH
2. Dibasic acids – HCl, H₂SO₄
3. Monobasic acids – HCl, HNO₃
4. Inorganic acids – HCOOH, H₂CO₃

Correct Answer: A [1 and 3 are correct]

Explanation:

HCOOH and CH3COOH are organic acids and HCl and HNO3 are monobasic, whereas HCl is not dibasic and H2SO4 is an inorganic acid, so 1 and 3 are correct.

26.  
CTS (ITI Posts) 2024
Assertion [A]: Orthophosphoric acid is a tribasic acid.
Reason [R]: It gives two hydrogen ions per molecule of the acid in aqueous solution.

Correct Answer: A [[A] is true but [R] is false]

Explanation:

Orthophosphoric acid (H3PO4) is tribasic because it gives three H+ ions, so the reason that it gives two H+ ions is false.

27.  
Field Surveyor 2022
Assertion [A]: Acetic acid is a weak acid.
Reason [R]: Acetic acid has four hydrogen atoms but only one can be replaced.

Correct Answer: B [[A] and [R] are correct; [R] does not explain [A]]

Explanation:

Acetic acid ionises only partially so it is weak, and only the H of the COOH group is replaceable although it has four hydrogens, but this does not explain its weakness.

28.  
Special Competitive Exam 2025
Match correctly the acids with their corresponding uses:
(a) Sulphuric acid – 1. Food preservatives
(b) Citric acid – 2. Constituent of baking powder
(c) Carbonic acid – 3. Car batteries
(d) Tartaric acid – 4. Aerated drinks

Correct Answer: B [3 1 4 2]

Explanation:

Sulphuric acid is used in car batteries, citric acid as a food preservative, carbonic acid in soda drinks and tartaric acid in baking powder, giving 3 1 4 2.

29.  
Group 4 2024
The acids present in grape and tomato are ______ and ______.

Correct Answer: C [Tartaric acid, oxalic acid]

Explanation:

Grapes contain tartaric acid and tomatoes contain oxalic acid.

30.  
AAO & AHO 2024
The compound used to clean iron deposits on quartz crystals is

Correct Answer: D [Oxalic acid]

Explanation:

Oxalic acid forms soluble complexes with iron, so it removes iron and rust stains from quartz crystals.

31.  
Group 1 2024
Among the following, which will have the highest dissociation constant (Ka) value?

Correct Answer: D [HClO₃]

Explanation:

Acid strength of oxoacids rises with more oxygen atoms on the same halogen, so HClO3 has the highest Ka.

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