1. Which of the following instruments is used in detecting the presence of radiation?

A. Cathode ray tube

B. Geiger–Muller counter ✔

C. Mass spectrometer

D. X-ray tube

Explanation:
A Geiger–Muller counter is specifically designed to detect ionizing radiation.

2. The molecule which has a linear shape is

A. $CH_4$

B. $NH_3$

C. $H_2S$

D. $CO_2$ ✔

Explanation:
$CO_2$ has two bonding regions around carbon and no lone pairs, giving a linear shape.

3. The formula of the compound formed between a trivalent metal $M$ and a divalent non-metal $Y$ is

A. $M_2Y_3$ ✔

B. $M_3Y_2$

C. $MY$

D. $M_3Y$

Explanation:
Balancing charges: $M^{3+}$ and $Y^{2-}$ gives $M_2Y_3$.

4. An atom of an element $X$ gains two electrons. The symbol of the ion formed is

A. $X^+$

B. $X^{2+}$

C. $X^{2-}$ ✔

D. $X^-$

Explanation:
Gaining electrons produces a negative ion with charge $2-$.

5. Which of the following statements is correct?

A. Atomic size decreases down the group

B. Atomic size increases across the period

C. Anions are smaller than the parent atom

D. Cations are smaller than the parent atom ✔

Explanation:
Cations lose electrons, reducing electron–electron repulsion and size.

6. Which of the following arrangements represents the correct order of electronic energy levels?

A. $1s\,2p\,2s\,3p\,3s\,3d$

B. $1s\,2s\,2p\,3s\,3p\,3d\,4s$ ✔

C. $1s\,2s\,2p\,3s\,3p\,4s\,3d$

D. $1s\,2s\,3s\,2p\,3p\,4s\,3d$

Explanation:
Electrons fill orbitals in increasing energy order according to the Aufbau principle.

7. The element with electron configuration $1s^2\,2s^2\,2p^6\,3s^2\,3p^1$ belongs to

A. s-block, period 3, group 1

B. p-block, period 3, group 2

C. s-block, period 3, group 3

D. p-block, period 3, group 3 ✔

Explanation:
The last electron enters a $p$ orbital; it is in period 3 and group 13.

8. In the periodic table, all the elements within the same group have the same

A. number of neutrons

B. number of valence electrons ✔

C. number of isotopes

D. atomic number

Explanation:
Elements in the same group have the same number of outer-shell electrons.

9. Which of the following halogens is liquid at room temperature?

A. Iodine

B. Chlorine

C. Bromine ✔

D. Fluorine

Explanation:
Bromine is the only halogen that exists as a liquid at room temperature.

10. Rare gases are stable because they

A. are chemically active

B. contain equal numbers of protons and neutrons

C. contain more electrons than protons

D. have octet structures ✔

Explanation:
Noble gases have complete valence shells, making them chemically inert.

11. In the periodic table, alkaline earth metals are found in group

A. I

B. II ✔

C. VI

D. VII

Explanation:
Alkaline earth metals occupy Group II of the periodic table.

12. In which of the following series are the atoms arranged in order of increasing ionization energy?

A. Li, Na, K

B. B, Be, Li

C. Be, Mg, Ca ✔

D. Na, Li, Be

Explanation:
Ionization energy decreases down the group; hence Ca < Mg < Be.

13. Which bond type is responsible for the high boiling point of water?

A. Metallic bond

B. Covalent bond

C. Ionic bond

D. Hydrogen bond ✔

Explanation:
Strong intermolecular hydrogen bonding increases water’s boiling point.

14. In metallic solids, the force of attraction is between mobile valence electrons and

A. atoms

B. neutrons

C. negative ions

D. positively charged nuclei ✔

Explanation:
Metallic bonding involves attraction between electrons and metal cations.

15. The bonds in crystalline ammonium chloride are

A. covalent and dative

B. ionic and covalent

C. ionic, covalent and dative ✔

D. ionic, covalent and hydrogen bond

Explanation:
$NH_4^+$ contains covalent and dative bonds, while ionic bonding exists between ions.

16. Which of the following elements is diatomic?

A. Sodium

B. Oxygen ✔

C. Iron

D. Neon

Explanation:
Oxygen exists naturally as $O_2$.

17. Noble gas molecules are held together by

A. van der Waals forces ✔

B. hydrogen bonds

C. dative bonds

D. covalent bonds

Explanation:
Weak van der Waals forces act between noble gas atoms.

18. Which statement about nuclear reactions is correct?

A. involves neutrons only

B. takes place inside the nucleus ✔

C. is governed by temperature and pressure

D. involves protons and electrons only

Explanation:
Nuclear reactions occur within the atomic nucleus.

19. Consider the reaction $C_2H_2 + yH_2 \rightarrow C_2H_6$. The value of $y$ is

A. 4

B. 3

C. 2 ✔

D. 1

Explanation:
Balancing hydrogen atoms gives $y = 2$.

20. The volume of $0.25\,\text{mol dm}^{-3}$ KOH solution that yields $6.5\,g$ of KOH is

A. $464.30\,cm^3$

B. $625.00\,cm^3$ ✔

C. $1000.00\,cm^3$

D. $2153.80\,cm^3$

Explanation:
Molar mass of KOH = $56\,g$.
Moles = $\frac{6.5}{56} = 0.116$.
Volume = $\frac{0.116}{0.25} = 0.464\,dm^3 = 464\,cm^3$.

21. The percentage by mass of calcium in $Ca(OCl)_2$ is
[Ca $= 40.0$, Cl $= 35.5$, O $= 16.0$]

A. $28.0\%$

B. $31.6\%$ ✔

C. $43.8\%$

D. $44.5\%$

Explanation:
Molar mass of $Ca(OCl)_2$:
$= 40 + 2(16 + 35.5) = 143$
Percentage of Ca $= \dfrac{40}{143} \times 100 = 27.97\% \approx 28.0\%$.

22. The gas law which describes the relationship between volume and temperature is

A. Boyle’s law

B. Charles’ law ✔

C. Dalton’s law

D. Graham’s law

Explanation:
Charles’ law states that volume is directly proportional to temperature at constant pressure.

23. Which of the following phenomena leads to a decrease in volume of a liquid in an open container?

A. Brownian motion

B. diffusion

C. evaporation ✔

D. sublimation

Explanation:
Evaporation causes liquid molecules to escape into the air, reducing volume.

24. The pressure exerted by a gas is a function of the

A. total volume of the gas

B. speed of gaseous molecules

C. mass of each gaseous molecule

D. frequency of collision between gaseous molecules ✔

Explanation:
Gas pressure results from collisions of molecules with the container walls.

25. Which of the following gases are arranged in increasing order of diffusion rate?
[H $=1$, C $=12$, N $=14$, O $=16$, S $=32$]

A. $SO_2$, $O_2$, $NH_3$, $H_2$ ✔

B. $H_2S$, $NH_3$, $O_2$, $SO_2$

C. $CO_2$, $N_2O$, $O_2$, $SO_2$

D. $NH_3$, $NO_2$, $NO_2$, $CO_2$

Explanation:
Diffusion rate increases as molar mass decreases. $SO_2 (64) > O_2 (32) > NH_3 (17) > H_2 (2)$.

26. Which variable is a measure of the average kinetic energy of gas molecules?

A. density

B. pressure

C. temperature ✔

D. volume

Explanation:
Temperature directly measures the average kinetic energy of molecules.

27. When heat is absorbed during a chemical reaction, the reaction is said to be

A. adiabatic

B. endothermic ✔

C. exothermic

D. isothermal

Explanation:
Endothermic reactions absorb heat from the surroundings.

28. The aqueous solution which has $pH > 7$ is

A. $FeCl_{3(aq)}$

B. $CuSO_{4(aq)}$

C. $KNO_{3(aq)}$

D. $Na_2CO_{3(aq)}$ ✔

Explanation:
$Na_2CO_3$ forms an alkaline solution in water.

29. Which of the following acids would readily react with $CaCO_3$ to liberate $CO_2$?

A. $CH_3COOH$

B. $H_2SO_4$

C. $H_2SO_3$

D. $HNO_3$ ✔

Explanation:
Strong acids like nitric acid readily react with carbonates.

30. Which of the following compounds crystallizes without water of crystallization?

A. $MgSO_4$

B. $Na_2CO_3$

C. $NaCl$ ✔

D. $FeSO_4$

Explanation:
Sodium chloride forms anhydrous crystals.

31. A substance is said to be impure if

A. its melting point range is wide ✔

B. it dissolves in water with difficulty

C. it has a low melting point

D. it is coloured

Explanation:
Impurities broaden the melting point range of a substance.

32. The following factors affect the solubility of a solid in a solvent except

A. nature of solute

B. nature of solvent

C. pressure ✔

D. temperature

Explanation:
Pressure has negligible effect on the solubility of solids.

33. Consider the equilibrium:
$N_2O_{4(g)} \rightleftharpoons 2NO_{2(g)} \quad \Delta H = +x\,kJ\,mol^{-1}$

What happens when the temperature is reduced at equilibrium?

A. concentration of $N_2O_{4(g)}$ decreases

B. concentration of $N_2O_{4(g)}$ increases ✔

C. pressure exerted by gases increases

D. pressure remains constant

Explanation:
Lowering temperature favours the exothermic (reverse) reaction, forming more $N_2O_4$.

34. Which of the following cells produce electrical energy from chemical reactions?

I. Lead-acid battery
II. Dry cell
III. Daniell cell
IV. Electrolytic cell

A. I and II only

B. I, II and III only ✔

C. II, III and IV only

D. I, III and IV only

Explanation:
Electrolytic cells consume electrical energy; the others produce it.

35. What happens at the cathode during electrolysis?

A. anion is oxidized

B. anion loses electrons

C. cation is oxidized

D. cation is discharged ✔

Explanation:
Cations gain electrons (are reduced) at the cathode.

36. Which of the following substances are electrolytes?

I. $PbBr_{2(l)}$
II. $NaCl_{(aq)}$
III. $NaCl_{(s)}$
IV. $C_6H_{12}O_{6(aq)}$

A. I and II only ✔

B. I, II and IV only

C. III and IV only

D. I and III only

Explanation:
Molten or aqueous ionic compounds conduct electricity.

37. Consider the redox reaction:
$I_{2(aq)} + 2S_2O_{3(aq)}^{2-} \rightarrow 2I^-_{(aq)} + S_4O_6^{2-}$

The species that is reduced is

A. $S_4O_6^{2-}$

B. $S_2O_3^{2-}$

C. $I_{2(aq)}$ ✔

D. $I^-_{(aq)}$

Explanation:
$I_2$ gains electrons to form $I^-$ and is therefore reduced.

38. The separation of petroleum fractions depends on differences in their

A. melting points

B. molar masses

C. solubilities

D. boiling points ✔

Explanation:
Fractional distillation separates substances by boiling points.

39. The major product formed by the reaction between ethanoic acid and aqueous sodium hydroxide is

A. soap

B. sodium ethanoate ✔

C. sodium methoxide

D. water

Explanation:
Neutralization produces sodium ethanoate and water.

40. Which of the following organic compounds would decolourize bromine water?

A. benzene

B. cyclobutane

C. hexane

D. pentene ✔

Explanation:
Unsaturated compounds like alkenes decolourize bromine water.