1. The negatively charged particle in an atom is the

A. electron ✔

B. neutron

C. positron

D. proton

Explanation:
Electrons carry a negative charge, while protons are positive and neutrons are neutral.

2. How many neutrons are contained in an atom with atomic number $6$ and mass number $12$?

A. $7$

B. $6$ ✔

C. $12$

D. $3$

Explanation:
Number of neutrons $= 12 - 6 = 6$.

3. The compound formed between $X_{14}$ and $Y_{16}$ is

A. $XY$

B. $XY_2$ ✔

C. $X_2Y$

D. $X_2Y_6$

Explanation:
$X_{14}$ has valency $4$ while $Y_{16}$ has valency $2$, so the formula is $XY_2$.

4. Van der Waals’ forces are the dominant intermolecular forces in

A. ammonium chloride

B. chlorine ✔

C. sodium chloride

D. water

Explanation:
Chlorine is a non-polar molecule, so weak van der Waals’ forces dominate.

5. The shape of a water molecule is

A. non-linear ✔

B. octahedral

C. pyramidal

D. tetrahedral

Explanation:
Water has two bonding pairs and two lone pairs, giving a bent (non-linear) shape.

6. A metallic ion with an inert gas structure contains $18$ electrons. How many protons does it contain?

A. $20$ ✔

B. $18$

C. $16$

D. $2$

Explanation:
A metal ion like $Ca^{2+}$ loses two electrons to have $18$ electrons, so it has $20$ protons.

7. Which of the following pairs of compounds belongs to the same homologous series?

A. $C_3H_6$ and $C_3H_6$

B. $C_4H_{10}$ and $C_5H_{10}$

C. $C_2H_4$ and $C_4H_{10}$

D. $C_2H_6$ and $C_4H_{10}$ ✔

Explanation:
Both compounds are alkanes and differ by a $CH_2$ unit.

8. Which of the following pairs of elements forms amphoteric oxides?

A. Be and Mg

B. Na and K

C. B and Al ✔

D. Si and Pb

Explanation:
Oxides of boron and aluminium can react with both acids and bases.

9. The following transition metal ions are coloured in aqueous solution except

A. $Cr^{3+}$

B. $Fe^{3+}$

C. $Mn^{3+}$

D. $Sc^{3+}$ ✔

Explanation:
$Sc^{3+}$ has no $d$-electrons and is therefore colourless.

10. The gas given off when ethanol reacts with sodium is

A. carbon(IV) oxide

B. hydrogen ✔

C. methane

D. oxygen

Explanation:
Alcohols react with sodium to produce hydrogen gas.

11. Which of the following halogens is solid at room temperature?

A. bromine

B. chlorine

C. fluorine

D. iodine ✔

Explanation:
Iodine exists as a solid at room temperature.

12. The alkaline earth metals have similar chemical properties because

A. they are in the same period

B. their salts are colourless

C. they have the same number of valence electrons ✔

D. they are very reactive

Explanation:
They all have two electrons in their outermost shell.

13. The number of unpaired electrons in an atom of element $Q_8$ is

A. $2$ ✔

B. $4$

C. $6$

D. $8$

Explanation:
Oxygen ($Z = 8$) has two unpaired electrons in its $2p$ orbitals.

14. The bond formed when ammonia reacts with hydrogen ion to form ammonium ion is

A. covalent

B. dative ✔

C. hydrogen bond

D. ionic

Explanation:
Ammonia donates a lone pair to $H^+$, forming a coordinate (dative) bond.

15. To which group and period respectively does an element with $15$ electrons belong?

A. $3$ and $3$

B. $3$ and $5$

C. $5$ and $3$ ✔

D. $5$ and $5$

Explanation:
An element with $15$ electrons is phosphorus, which is in group $5$, period $3$.

16. The shape of a graphite crystal is

A. tetrahedral

B. pyramidal

C. octahedral

D. hexagonal ✔

Explanation:
Graphite consists of layers of hexagonally arranged carbon atoms.

17. Which of the following oxides is ionic?

A. $P_4O_{10}$

B. $MgO$ ✔

C. $Al_2O_3$

D. $SO_2$

Explanation:
$MgO$ is formed from a metal and a non-metal, making it ionic.

18. Which of the following substances when boiled with aqueous sodium hydroxide would be hydrolysed?

I. Protein
II. Fat
III. Polythene

A. I

B. II

C. I and II ✔

D. II and III

Explanation:
Proteins and fats undergo hydrolysis in alkaline conditions.

19. Which trioxonitrate(V) salt decomposes on heating to form a metal?

A. $Cu(NO_3)_2$

B. $AgNO_3$ ✔

C. $Pb(NO_3)_2$

D. $KNO_3$

Explanation:
Silver nitrate decomposes to give metallic silver.

20. Consider the reaction:
$C_2H_{4(g)} + 3O_{2(g)} \rightarrow 2CO_{2(g)} + 2H_2O_{(g)}$

The volume of $CO_2$ produced at STP when $0.05$ moles of $C_2H_4$ reacts is

A. $1.12 \, dm^3$

B. $2.24 \, dm^3$ ✔

C. $3.72 \, dm^3$

D. $4.48 \, dm^3$

Explanation:
$1$ mole of $C_2H_4$ produces $2$ moles of $CO_2$.
Moles of $CO_2 = 0.05 \times 2 = 0.10$
Volume $= 0.10 \times 22.4 = 2.24 \, dm^3$.

21. The number of oxygen molecules present in $16.0\,g$ of the gas is
[Avogadro’s number $= 6.02 \times 10^{23}$]

A. $6.02 \times 10^{22}$

B. $6.02 \times 10^{23}$

C. $3.01 \times 10^{23}$ ✔

D. $1.51 \times 10^{23}$

Explanation:
Molar mass of $O_2 = 32\,g$.
Number of moles $= \dfrac{16}{32} = 0.5$.
Number of molecules $= 0.5 \times 6.02 \times 10^{23} = 3.01 \times 10^{23}$.

22. Consider the reaction:
$2H^+_{(aq)} + y e^- \rightarrow SO_3^{2-}{(aq)} + H_2O_{(l)}$

The value of $y$ is

A. $2$

B. $3$

C. $4$ ✔

D. $6$

Explanation:
Balancing charges gives $y = 4$ electrons.

23. The general gas equation was derived from

A. Boyle’s and Gay-Lussac’s laws

B. Boyle’s and Graham’s laws

C. Boyle’s and Charles’ laws ✔

D. Dalton’s atomic theory

Explanation:
The combined gas law results from Boyle’s and Charles’ laws.

24. The vapour pressure of a liquid depends on

I. temperature
II. rate of condensation
III. cohesive forces holding the particles together

A. I

B. I and II

C. I and III ✔

D. II and III

Explanation:
Vapour pressure increases with temperature and decreases with stronger intermolecular forces.

25. Which of the following gases will diffuse most rapidly?
[H = 1.0, C = 12.0, O = 16.0, S = 32.0, Cl = 35.5]

A. $Cl_2$

B. $SO_2$

C. $CH_4$ ✔

D. $C_2H_6$

Explanation:
According to Graham’s law, lighter gases diffuse faster. $CH_4$ has the lowest molar mass.

26. When a reaction is endothermic

A. enthalpy change $(\Delta H)$ is negative

B. heat content of products is less than reactants

C. heat content of reactants is less than that of products ✔

D. the reaction is non-spontaneous

Explanation:
Endothermic reactions absorb heat; products have higher energy.

27. Which statement about intermolecular distances and cohesive forces between gas molecules is correct?

A. both are large

B. both are negligible

C. constant and negligible

D. large and negligible ✔

Explanation:
Gas molecules are far apart and have negligible cohesive forces.

28. The rate curve for the reaction between magnesium and excess dilute $HCl$ becomes horizontal at point X because

A. the reaction was slowed down

B. all the dilute $HCl$ has reacted

C. all the magnesium has reacted ✔

D. hydrogen gas is produced at a steady rate

Explanation:
The reaction stops when all the magnesium is completely used up.

29. An example of an acid salt is

A. $CH_3COONa$

B. $Mg(OH)Cl$

C. $NaHSO_4$ ✔

D. $(NH_4)_2SO_4$

Explanation:
Acid salts still contain replaceable hydrogen ions.

30. Which of the following oxides can be reduced by hydrogen?

A. aluminium oxide

B. iron(III) oxide ✔

C. sodium oxide

D. silver oxide

Explanation:
Hydrogen reduces oxides of metals below it in the reactivity series, such as iron.

31. Solubility is practically applied in

A. fractional distillation

B. determination of pH

C. determination of saturation in hydrocarbons

D. solvent extraction ✔

Explanation:
Solvent extraction depends on differences in solubility.

32. Which of the following compounds is the least soluble in water?

A. $CaCl_2$

B. $CaSO_4$ ✔

C. $NaCl$

D. $Na_2SO_4$

Explanation:
$CaSO_4$ is only sparingly soluble in water.

33. A substance that dissolves readily in organic solvents would

A. be a covalent compound ✔

B. have strong electrostatic forces

C. have a high melting point

D. conduct electricity when molten

Explanation:
Organic solvents dissolve covalent compounds more easily.

34. Consider the equilibrium:
$2SO_{2(g)} + O_{2(g)} \rightleftharpoons 2SO_{3(g)}$

Addition of more $O_2$ shifts the equilibrium to the

A. right, producing more $SO_3$ ✔

B. right, producing more $SO_2$

C. left, producing more $SO_3$

D. left, producing more $SO_2$

Explanation:
According to Le Chatelier’s principle, adding a reactant shifts equilibrium to the product side.

35. A change in temperature of a saturated solution disturbs the equilibrium between the

A. undissolved solute and solvent

B. dissolved solute and solvent

C. dissolved solute and undissolved solute ✔

D. dissolved solute and solution

Explanation:
A saturated solution is in equilibrium between dissolved and undissolved solute.

36. Which statement about an electrochemical cell is correct?

Oxidation occurs

A. at the anode ✔

B. at the cathode

C. through the salt bridge

D. in the aqueous solution

Explanation:
Oxidation always occurs at the anode.

37. Consider the reaction:
$CuO_{(s)} + H_{2(g)} \rightarrow Cu_{(s)} + H_2O_{(l)}$

The substance oxidised is

A. $Cu$

B. $CuO$

C. $H_2$ ✔

D. $H_2O$

Explanation:
Hydrogen loses electrons (is oxidised) to form water.

38. Which of the following metals is the strongest reducing agent?

A. sodium

B. silver

C. potassium ✔

D. copper

Explanation:
Potassium is the most reactive metal listed.

39. The complete hydrogenation of benzene gives

A. cyclohexene

B. cyclohexane ✔

C. hexene

D. hexane

Explanation:
Complete hydrogenation saturates all double bonds to form cyclohexane.

40. A compound has an empirical formula $CH_2O$ and a molecular mass of $90$. Determine its molecular formula.

A. $C_4H_{10}O_2$

B. $C_3H_{10}O_2$

C. $C_3H_6O_3$ ✔

D. $C_2H_2O_4$

Explanation:
Empirical formula mass $= 12 + 2 + 16 = 30$
Multiplier $= \frac{90}{30} = 3$
Molecular formula $= C_3H_6O_3$.

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