PES SS 3 Chemistry Obj Mock 1 Exam 2026-27

1. The hydrolysis of proteins by diluting mineral acids produces

A) fatty acids
B) sucrose
C) amino acids
D) glucose

2. Which of the following oxide causes acid rain?

A) CO
B) NO₂
C) NO
D) H₂O₂

3. The ratio of carbon atoms of hydrogen atoms in a hydrocarbon is 1:2. If its molecular mass is 56, what is its molecular formula?

A) C₃H₆
B) C₂H₄
C) CH₂
D) C₄H₈

4. What is the relative molecular mass of the compound below?

A) 59
B) 136
C) 137
D) 64

5. Cathodic protection of metals is based on

A) relative tendencies of oxidation
B) nature of oxides formed
C) standard electrode potential of hydrogen
D) its electrical conductivity

6. If humid air is polluted by chlorine discharged, the air can be restored by sprinkling

A) acidified KMnO₄
B) acidified FeSO₄
C) saturated NaCl(aq)
D) solid MnO₂

7. The alkanol represented by the structure above is

A) secondary and monohydric
B) secondary and dihydric
C) tertiary and dihydric
D) primary and dihydric

8. Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?

A) NH₄NO₃ and Na₂CO₃
B) K₂SO₄ and BaCl₂
C) NaCl and KNO₃
D) KCl and NaNO₃

9. Study the graphs below (I, II, III, IV) and use them to answer questions 9 to 11.

Which of the graphs illustrates the variation of the rate of evolution of a gas from a given length of magnesium ribbon (y-axis) with increase in the concentration of the acid added (x-axis)?

A) I
B) IV
C) III
D) II

10. Study the graphs below (I, II, III, IV) and use them to answer questions 9 to 11.

Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution (y-axis) with the volume of strong base titrated against it (x-axis)?

A) IV
B) I
C) III
D) II

11. Study the graphs below (I, II, III, IV) and use them to answer questions 9 to 11.

Which of the graphs illustrates the variation of the solubility of a salt in water (y-axis) with increase in temperature (x-axis), if the dissolution process is exothermic?

A) II
B) III
C) IV
D) I

12. The formation of ethene from dehydration of ethanol can be described as

A) an elimination reaction.
B) an addition reaction.
C) an oxidation reaction.
D) a substitution reaction.

13. Which of the following gases is highly soluble in water at room temperature?

A) Chlorine
B) Nitrogen
C) Carbon (IV) oxide
D) Ammonia

14. A molecule of phosphorus is

A) a tetraatomic.
B) a diatomic.
C) a monoatomic.
D) a triatomic.

15. The most common method of preparing insoluble salts is by

A) double decomposition.
B) neutralization.
C) decomposition.
D) filtration.

16. What number of moles of oxygen would exert a pressure of 10 atm at 320K in an 8.2dm³ cylinder? [R=0.082 atm dm³mol⁻¹K⁻¹]

A) 1.56
B) 3.13
C) 31.25
D) 0.32

17. The basic property of salts used as drying agents is

A) low solubility.
B) efflorescence.
C) high melting point.
D) hygroscopy.

18. What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper (II) ions?

A) A green precipitate is formed which is insoluble in excess ammonia
B) A blue precipitate is formed which is soluble in excess ammonia
C) A white precipitate is formed which is soluble in excess ammonia
D) A brick red precipitate is produced which is insoluble in excess ammonia

19. When CuSO4(aq) is added to Pb(NO3)2(aq),

A) there would be no visible change.
B) a white precipitate would be formed.
C) a blue precipitate would be formed.
D) the resulting solution would become colourless.

20. Consider the structure below (a carbon chain with -OH, a C₂H₅ branch, and a C=O group). How many carbon atoms does the parent chain contain?

A) 4
B) 3
C) 2
D) 5

21. Under which conditions of pressure (P) and temperature (T) would the volume of an inflated balloon increase? When

A) T is increased and P is decreased
B) both T and P are decreased
C) T is decreased and P is increased
D) both T and P are increased

22. The collision between ideal gas molecules are considered to be perfectly elastic because

A) the distance between them is large compared to their sizes.
B) they move randomly in straight lines.
C) their average kinetic energy is variable.
D) they collide without losing energy.

23. Elements with high ionization energies would

A) have large atomic radii.
B) have low atomic numbers.
C) lose electrons easily.
D) have high effective nuclear charges.

24. Which of the following statements about Group VII elements is correct?

A) They are present in the same physical state
B) Their reactivity decreases down the group
C) They exist as monoatomic molecules
D) They are strong reducing agents

25. Consider the diagram below and use it to answer questions 25 and 26 (electrochemical cell with crystals A and B, A(aq)3+ and B(aq)2+).

Which of the following cell notations represent the diagram?

A) B/B2+//A/A3+
B) A/A3+//B2+/B
C) B2+/B//A/A3+
D) A3+/A//B/B2+

26. Consider the diagram below and use it to answer questions 25 and 26 (electrochemical cell with crystals A and B, A³⁺ (aq) and B²⁺ (aq).

Which of the following half reaction equations represent the reaction at the cathode?

A) A(s)→A3+(aq)+3e⁻
B) A3+(aq)+3e⁻→A(s)
C) B2+(aq)+2e⁻→B(s)
D) B(s)→B2+(aq)+2e⁻

27. The reactivity of fluorine is high because of

A) the strong F-F bond.
B) its high electronegativity.
C) the availability of d-orbitals.
D) the small size of the fluorine atom.

28. How many coulombs of electricity would liberate 1.08g of Ag from a solution of silver salt? [Ag=108.0; 1F=96500C]

A) 965C
B) 9650C
C) 96500C
D) 9.65C

29. The Bohr model of the atom proposed

A) neutrons.
B) electron shells.
C) nucleons.
D) the existence of the nucleus.

30. At 25°C, evaporation of a 100cm³ solution of K2CO₃ to dryness gave 14g of the salt. What is the solubility of K2CO₃ at 25°C? [K2CO3=138]

A) 0.01 mol dm⁻³
B) 0.101 mol dm⁻³
C) 1.01 mol dm⁻³
D) 10.0 mol dm⁻³

31. Student X titrated 25cm³ of Na₂CO₃ with 0.1mol dm⁻³ HCl, using methyl orange as indicator. Student Y carried out the same exercise but used phenolphthalein as indicator. Which of the following statements about the titration is true?

A) Hydrogen chloride gas was released in the reactions in both titrations
B) The titre value obtained by Y is twice that of X
C) The titre value obtained by X is twice that of Y
D) The titre values obtained from the titrations are equal

32. What is the concentration of a solution which contains 0.28g of potassium hydroxide in 100cm³ of solution? [KOH=56]

A) 0.10 mol dm⁻³
B) 0.50 mol dm⁻³
C) 0.01 mol dm⁻³
D) 0.05 mol dm⁻³

33. What is the empirical formula of a hydrocarbon containing 0.160 moles of carbon and 0.640 moles of hydrogen?

A) CH₄
B) CH₃
C) CH₂
D) C₂H₄

34. Which of the following species has the largest ionic radius?

A) Ca2+
B) S2-
C) K+
D) Cl-

35. Which of the following statements is correct about ionization energy? It

A) decreases down the group
B) decreases across the periods
C) causes metallic nuclei to disintegrate
D) results in the formation of an anion

36. Potassium trioxonitrate (V) can be obtained from its solution by

A) distillation.
B) filtration.
C) crystallization.
D) evaporation.

37. An element, Q, contains 69.0% of 63Q and 31% of 65Q. What is the relative atomic mass of Q?

A) 63.0
B) 69.0
C) 63.6
D) 65.0

38. The following ions have the same electron configuration except ____

A) Al³⁺
B) O^2-
C) Cl⁻
D) Mg²⁺

39. The region around the nucleus where electrons can be located is called

A) a spectra.
B) a field.
C) an orbital.
D) a quanta.

40. Protons and electrons are called fundamental particles because they

A) are the lightest particles.
B) are found in all matter.
C) have different charges.
D) are indivisible.

41. Consider the following energy profile diagram (Potential Energy vs Reaction Co-ordinates) and use it to answer questions 41 to 43.

The activation energy of the reaction is

A) EB
B) ED
C) EA
D) EC

42. Consider the following energy profile diagram (Potential Energy vs Reaction Co-ordinates) and use it to answer questions 41 to 43.

The enthalpy change of the reaction is

A) EC
B) EA
C) ED
D) EB

43. Consider the following energy profile diagram (Potential Energy vs Reaction Co-ordinates) and use it to answer questions 41 to 43.

The energy profile diagram illustrates

A) an exothermic reaction.
B) an endothermic reaction.
C) a redox reaction.
D) a spontaneous reaction.

44. How many molecules of oxygen would occupy a volume of 2.24cm³ at s.t.p.?
[Molar volume at s.t.p.=22,400cm³;
Avogadro's number = 6.02×10²³]

A) 6.02×10¹⁹
B) 3.01×10²¹
C) 3.01×10²⁰
D) 6.02×10²⁷

45. The relationship between x, y and z is

A) x<z<y.
B) x=y=z.
C) xy<z.
D) x>y>z.

46. Which of the following pairs of molecules form hydrogen bonds?

A) H₂S and CH₄
B) NH₃ and SO₂
C) C₂H₅OH and CH₃OH
D) C₆H₆ and Br₂

47. Which of the following statements about elements in Group VII is correct?

A) F₂ has the least tendency to be reduced
B) Cl₂ will oxidize I⁻
C) Br will oxidize Cl⁻
D) I₂ is a stronger oxidizing agent than F₂

48. Electrovalent compounds normally

A) have low boiling points.
B) dissolve in polar solvents.
C) have mobile electrons.
D) conduct electricity in the solid state.

49. A coordinate covalent bond could be formed between

A) NH3 and PCl3.
B) H+ and AlCl3.
C) BCl3 and NH3.
D) BCl3 and AlCl3.

50. Which of the following scientists discovered the electron?

A) Joseph J. Thompson
B) Ernest Rutherford
C) Amedeo Avogadro
D) James Chadwick

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