20/09/2026
Chemistry — 45 MCQs MDCAT 2026
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1. Complete combustion of 1 mole of ethene requires how many moles of O₂?
A) 1 mol
B) 2 mol
C) 3 mol
D) 4 mol
Answer: C
2. Which molecule has the highest dipole moment among the following?
A) C₄H₁₀
B) CO₂
C) CH₄
D) NH₃
Answer: D
3. Standard atmospheric pressure at sea level is:
A) 760 cm Hg
B) 101.325 kPa
C) 760 bar
D) 101325 torr
Answer: B
4. Oxidation of an aldehyde with acidified K₂Cr₂O₇ generally produces:
A) Alcohol
B) Ketone
C) Carboxylic acid
D) Ether
Answer: C
5. How many sigma bonds are present between the two carbon atoms of ethyne?
A) 0
B) 1
C) 2
D) 3
Answer: B
6. The geometry around an sp²-hybridized carbon atom is:
A) Linear
B) Tetrahedral
C) Trigonal planar
D) Trigonal pyramidal
Answer: C
7. As bond length generally increases, bond energy:
A) Increases
B) Remains constant
C) Decreases
D) First increases then decreases
Answer: C
8. Phenol primarily undergoes which type of reaction on its aromatic ring?
A) Nucleophilic substitution
B) Electrophilic substitution
C) Elimination
D) Addition
Answer: B
9. The solubility of CaCl₂ is 0.02 mol L⁻¹. Its Ksp is:
A) 8.0 × 10⁻⁶
B) 1.6 × 10⁻⁵
C) 3.2 × 10⁻⁵
D) 6.4 × 10⁻⁵
Answer: C
10. For gases at identical temperature and pressure, which contains the greatest number of molecules?
A) 1 dm³ He
B) 2 dm³ Ne
C) 3 dm³ O₂
D) 1 dm³ N₂
Answer: C
11. Controlled reduction of an acyl chloride can produce:
A) Alkane
B) Aldehyde
C) Ketone
D) Ether
Answer: B
12. The oxidation state of hydrogen in BeH₂ is:
A) +1
B) 0
C) −1
D) −2
Answer: C
13. Alkali metals react with water to form:
A) Metal oxide + oxygen
B) Metal peroxide + H₂O
C) Metal hydroxide + H₂
D) Metal hydride + O₂
Answer: C
14. (CH₃)₃C–OH is classified as a:
A) Primary alcohol
B) Secondary alcohol
C) Tertiary alcohol
D) Phenol
Answer: C
15. The IUPAC name of CH₃CH(CH₃)CH₂CH(CH₂CH₃)CH₃ is:
A) 2,4-Dimethylhexane
B) 3-Ethyl-2-methylpentane
C) 2,4-Dimethylheptane
D) 3,5-Dimethylheptane
Answer: A
16. The carbonyl carbon of a ketone is:
A) sp, linear
B) sp², trigonal planar
C) sp³, tetrahedral
D) sp³, pyramidal
Answer: B
17. Which substituent is strongly ortho/para directing?
A) –CN
B) –COOH
C) –CHO
D) –OH
Answer: D
18. A gas occupies 400 mL at 226°C. What volume will it occupy at 127°C at constant pressure?
A) 267 mL
B) 300 mL
C) 321 mL
D) 500 mL
Answer: C
19. 64 g CH₄ occupies 44.8 L at 2 atm. Its approximate temperature is:
A) 127 K
B) 273 K
C) 373 K
D) 546 K
Answer: B
20. Anisotropy means that a property:
A) Is independent of direction
B) Is independent of temperature
C) Varies with direction
D) Is independent of pressure
Answer: C
21. Phenol treated with excess nitrating mixture gives:
A) Nitrobenzene
B) 2-Nitrophenol only
C) 2,4,6-Trinitrophenol
D) Benzoic acid
Answer: C
22. Methane reacts with chlorine in the presence of:
A) Dark and cold conditions
B) Water
C) UV light/sunlight
D) Concentrated H₂SO₄
Answer: C
23. Which statement correctly compares ethene and ethyne hybridization?
A) Both are sp
B) Ethene is sp and ethyne is sp²
C) Ethene is sp² and ethyne is sp
D) Both are sp³
Answer: C
24. The reactant that is completely consumed first and determines the maximum amount of product is called:
A) Excess reactant
B) Catalyst
C) Limiting reactant
D) Intermediate
Answer: C
25. If 500 J heat is absorbed and 850 J work is done on the system, ΔU is:
A) −350 J
B) +350 J
C) +1350 J
D) −1350 J
Answer: C
26. Compared with reactants, products of an exothermic reaction generally have:
A) Higher enthalpy
B) Lower enthalpy
C) Equal enthalpy
D) Zero enthalpy
Answer: B
27. Which of the following decreases activation energy?
A) Increasing temperature
B) Increasing pressure
C) Adding a catalyst
D) Increasing concentration
Answer: C
28. If doubling [A] doubles the rate and doubling [B] increases the rate fourfold, the rate law is:
A) Rate = k[A]²[B]
B) Rate = k[A][B]
C) Rate = k[A][B]²
D) Rate = k[A]²[B]²
Answer: C
29. If Rate = k[A]²[B], and both [A] and [B] are tripled, the rate becomes:
A) 3 times
B) 9 times
C) 27 times
D) 81 times
Answer: C
30. Which does NOT change the position of a chemical equilibrium?
A) Change in concentration
B) Change in pressure
C) Change in temperature
D) Addition of a catalyst
Answer: D
31. The decomposition of N₂O₅ is commonly treated as:
A) Zero order
B) First order
C) Second order
D) Third order
Answer: B
32. Which substituent is deactivating but directs electrophilic substitution mainly to ortho/para positions?
A) –OH
B) –COOH
C) –Cl
D) –CN
Answer: C
33. The IUPAC name of CH₃CH₂Cl is:
A) Chloromethane
B) Chloroethane
C) Ethyl chloride
D) 1-Chloropropane
Answer: B
34. Which is an addition polymer?
A) Nylon-6,6
B) Polyester
C) PVC
D) Nylon-6,10
Answer: C
35. CH₃CH₂COOH + C₂H₅OH produces an ester by:
A) Hydrolysis
B) Oxidation
C) Esterification
D) Reduction
Answer: C
36. 1-Butene reacts with Br₂ to form:
A) 1-Bromobutane
B) 2-Bromobutane
C) 1,2-Dibromobutane
D) 1,1-Dibromobutane
Answer: C
37. Average kinetic energy of gas molecules is directly proportional to:
A) Celsius temperature
B) Pressure only
C) Volume only
D) Absolute temperature
Answer: D
38. For singly charged He⁺ and O⁺ ions, the ratio (e/m)He : (e/m)O is:
A) 1:4
B) 1:2
C) 4:1
D) 2:1
Answer: C
39. The principal quantum number n primarily indicates:
A) Orbital orientation
B) Electron spin
C) Main energy level and approximate orbital size
D) Orbital shape only
Answer: C
40. The ground-state electronic configuration of chromium (Z = 24) is:
A) [Ar] 3d⁴4s²
B) [Ar] 3d⁶4s⁰
C) [Ar] 3d⁵4s¹
D) [Ar] 3d³4s³
Answer: C
41. Across a period from left to right, atomic radius generally:
A) Increases
B) Decreases
C) Remains constant
D) First increases then remains constant
Answer: B
42. Across the first transition series from Sc to Zn, the shielding effect of added 3d electrons:
A) Decreases markedly
B) Increases slightly
C) Remains exactly constant
D) Increases dramatically
Answer: B
43. A species with a more positive standard reduction potential has a greater tendency to:
A) Lose electrons
B) Gain electrons
C) Lose protons
D) Undergo oxidation
Answer: B
44. Ionic character of a bond is most closely related to:
A) Atomic mass difference
B) Ionization energy alone
C) Electron affinity alone
D) Electronegativity difference
Answer: D
45. The rule stating that degenerate orbitals are singly occupied with parallel spins before pairing is:
A) Aufbau principle
B) Pauli exclusion principle
C) Hund's rule
D) Heisenberg uncertainty principle
Answer: C
