NEET UG - Preparation properties and uses of K2Cr2O7 and KMnO4, lanthanoids and actinoids electronic configurations and oxidation states Online Test (MCQ Quiz)

1. What is the primary method for the industrial preparation of potassium dichromate (K2Cr2O7)?

A) Direct oxidation of chromite ore with air B) Fusion of chromite ore (FeCr2O4) with sodium carbonate and limestone in the presence of air C) Electrolytic reduction of chromium(III) oxide D) Reaction of potassium chromate with sulfuric acid

2. In the preparation of potassium dichromate, chromite ore is first converted to sodium chromate. What is the chemical equation for this step?

A) 4FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2 B) 2FeCr2O4 + 4Na2CO3 + O2 → 2Na2CrO4 + Fe2O3 + 4CO2 C) FeCr2O4 + Na2CO3 + O2 → Na2CrO4 + FeO + CO2 D) 4FeCr2O4 + Na2CO3 + O2 → Na2CrO4 + 2Fe2O3 + CO2

3. The conversion of sodium chromate (Na2CrO4) to sodium dichromate (Na2Cr2O7) in the preparation of K2Cr2O7 involves acidification. What is the role of acid in this step?

A) To oxidize chromate ions to dichromate ions B) To reduce dichromate ions to chromate ions C) To convert chromate ions into dichromate ions by protonation D) To precipitate sodium dichromate

4. What is the purpose of adding sulfuric acid to sodium dichromate solution to obtain potassium dichromate?

A) To reduce dichromate to chromate B) To oxidize dichromate to Cr(VI) species C) To precipitate potassium dichromate due to its lower solubility compared to sodium dichromate D) To act as a catalyst for the reaction

5. Potassium dichromate (K2Cr2O7) is a strong oxidizing agent. In acidic medium, which species is formed when dichromate ion (Cr2O7^2-) acts as an oxidizing agent?

A) CrO4^2- B) Cr^3+ C) Cr^2+ D) CrO3

6. What is the change in oxidation state of chromium when K2Cr2O7 acts as an oxidizing agent in acidic solution?

A) +6 to +2 B) +6 to +3 C) +3 to +6 D) +2 to +6

7. Which of the following reactions best illustrates the oxidizing property of K2Cr2O7 in acidic medium?

A) Cr2O7^2- + 6Fe^2+ + 14H+ → 2Cr^3+ + 6Fe^3+ + 7H2O B) Cr2O7^2- + 2OH- → 2CrO4^2- + H2O C) 2CrO4^2- + 2H+ → Cr2O7^2- + H2O D) Cr2O7^2- + 3SO2 + H2O → 2Cr^3+ + 3SO4^2- + 2H+

8. Potassium dichromate is used in various applications. Which of the following is NOT a typical use of K2Cr2O7?

A) Mordant in dyeing and printing textiles B) Oxidizing agent in titration and organic synthesis C) Manufacturing of pigments D) Production of fertilizers

9. How is potassium permanganate (KMnO4) typically prepared industrially from pyrolusite ore (MnO2)?

A) Fusion of MnO2 with potassium hydroxide in the presence of air or oxygen B) Electrolytic oxidation of MnO2 in acidic solution C) Reaction of MnO2 with concentrated nitric acid D) Direct reaction of MnO2 with potassium carbonate

10. In the preparation of KMnO4, the first step involves the fusion of MnO2 with KOH and an oxidizing agent. What is the intermediate product formed?

A) Potassium manganate (K2MnO4) B) Manganese dioxide (MnO2) C) Potassium permanganate (KMnO4) D) Manganese(III) oxide (Mn2O3)

11. The conversion of potassium manganate (K2MnO4) to potassium permanganate (KMnO4) can be achieved by oxidation. Which method is commonly used?

A) Electrolytic oxidation B) Oxidation with chlorine gas C) Oxidation with ozone D) All of the above

12. Potassium permanganate (KMnO4) is a powerful oxidizing agent. What is the color of the permanganate ion (MnO4^-)?

A) Yellow B) Green C) Purple D) Orange

13. The oxidizing strength of KMnO4 varies with pH. In acidic medium, MnO4^- is reduced to which species?

A) MnO2 B) Mn^2+ C) MnO4^2- D) Mn^3+

14. What is the change in oxidation state of manganese when KMnO4 acts as an oxidizing agent in acidic solution?

A) +7 to +4 B) +7 to +2 C) +7 to +3 D) +4 to +2

15. In neutral or faintly alkaline solution, MnO4^- is reduced to which species?

A) Mn^2+ B) MnO2 C) MnO4^2- D) Mn^3+

16. Which reaction demonstrates the oxidizing property of KMnO4 in neutral/faintly alkaline medium?

A) 2MnO4^- + 5SO2 + 2H2O → 2Mn^2+ + 5SO4^2- + 4H+ B) 2MnO4^- + 3SO3^2- + H2O → 2MnO2 + 3SO4^2- + 2OH- C) MnO4^- + 4H+ + 3e- → MnO2 + 2H2O D) MnO4^- + 2H2O + 3e- → MnO2 + 4OH-

17. Potassium permanganate is widely used as an oxidizing agent. Which of the following is a significant application of KMnO4?

A) Bleaching of wood pulp B) Water purification C) Organic synthesis (e.g., oxidation of alkenes) D) All of the above

18. Lanthanoids are a series of elements characterized by the filling of which subshell?

A) 4f B) 5f C) 3d D) 4d

19. What is the general electronic configuration of lanthanoids?

A) [Xe] 4f^1-14 5d^0-1 6s^2 B) [Xe] 5f^1-14 6d^0-1 7s^2 C) [Kr] 4f^1-14 5d^0-1 6s^2 D) [Rn] 5f^1-14 6d^0-1 7s^2

20. Which element marks the beginning of the lanthanoid series?

A) Lanthanum (La) B) Cerium (Ce) C) Lutetium (Lu) D) Ytterbium (Yb)

21. Lanthanum (atomic number 57) has the electronic configuration [Xe] 5d^1 6s^2. Cerium (atomic number 58) has the electronic configuration [Xe] 4f^1 5d^1 6s^2. This indicates that the filling of the 4f subshell starts from which element?

A) Lanthanum B) Cerium C) Praseodymium D) Neodymium

22. The most common oxidation state exhibited by lanthanoids is:

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

23. Which of the following lanthanoids commonly exhibits an oxidation state of +4 in addition to +3?

A) Europium (Eu) B) Ytterbium (Yb) C) Cerium (Ce) D) Holmium (Ho)

24. Europium (Eu, Z=63) has the electronic configuration [Xe] 4f^7 6s^2. It commonly exhibits an oxidation state of +2. This is due to the stability of:

A) Partially filled 4f subshell B) Completely filled 4f subshell C) Half-filled 4f subshell D) Empty 4f subshell

25. Ytterbium (Yb, Z=70) has the electronic configuration [Xe] 4f^14 6s^2. It commonly exhibits an oxidation state of +2. This is due to the stability of:

A) Partially filled 4f subshell B) Completely filled 4f subshell C) Half-filled 4f subshell D) Empty 4f subshell

26. What is the primary characteristic that leads to the similar chemical properties of lanthanoids?

A) Involvement of 4f electrons in bonding B) Similar electronic configurations of valence shells (6s^2) C) Presence of unpaired electrons in 4f orbitals D) Difference in atomic radii

27. Lanthanoid contraction refers to the gradual decrease in atomic and ionic radii across the lanthanoid series. What is the main reason for this contraction?

A) Poor shielding of the nuclear charge by 4f electrons B) Effective shielding of the nuclear charge by 5d electrons C) Increase in the number of valence electrons D) Decrease in the number of neutrons

28. Actinoids are a series of elements characterized by the filling of which subshell?

A) 4f B) 5f C) 3d D) 6d

29. What is the general electronic configuration of actinoids?

A) [Xe] 4f^1-14 5d^0-1 6s^2 B) [Xe] 5f^1-14 6d^0-1 7s^2 C) [Rn] 4f^1-14 5d^0-1 6s^2 D) [Rn] 5f^1-14 6d^0-1 7s^2

30. Which element is considered the first member of the actinoid series?

A) Actinium (Ac) B) Thorium (Th) C) Uranium (U) D) Lawrencium (Lr)

31. Actinoids are generally more reactive than lanthanoids. What is a contributing factor to this difference in reactivity?

A) Lower ionization enthalpies of actinoids B) Higher ionization enthalpies of actinoids C) More stable 5f orbitals compared to 4f orbitals D) Less effective shielding by 5f electrons

32. The oxidation states exhibited by actinoids are more variable than those of lanthanoids. Which of the following is a common oxidation state for actinoids besides +3?

A) +2 B) +4 C) +5 D) All of the above

33. Thorium (Th, Z=90) has the electronic configuration [Rn] 6d^2 7s^2. It primarily exhibits an oxidation state of +4. What is the likely reason?

A) Involvement of 5f electrons B) Involvement of 6d electrons C) Stability of completely filled 5f subshell D) Stability of half-filled 5f subshell

34. Uranium (U, Z=92) exhibits several oxidation states, including +3, +4, +5, and +6. This variability is characteristic of:

A) Lanthanoids B) Actinoids C) Transition metals D) Inner transition metals

35. All actinoids are radioactive. This is a key difference from lanthanoids, where only promethium (Pm) is radioactive.

A) True, all actinoids are radioactive B) False, only some actinoids are radioactive C) True, but only the first few actinoids are radioactive D) False, lanthanoids are generally more radioactive

36. Which statement accurately compares lanthanoids and actinoids regarding their electronic configurations?

A) Lanthanoids involve filling of 4f orbitals, while actinoids involve filling of 5f orbitals. B) Lanthanoids involve filling of 5f orbitals, while actinoids involve filling of 4f orbitals. C) Both involve filling of d orbitals. D) Both involve filling of p orbitals.

37. Due to the actinoid contraction, the atomic radii of elements following the actinoid series are expected to:

A) Increase significantly B) Decrease significantly C) Show a less pronounced decrease compared to lanthanoid contraction D) Remain relatively constant

38. Which of the following is a common use of potassium dichromate in laboratories?

A) As a primary standard in redox titrations B) As a drying agent C) As a catalyst in esterification D) As a source of oxygen gas

39. Potassium permanganate solution is often standardized before use in titrations. What is a common substance used for its standardization?

A) Sodium oxalate (Na2C2O4) B) Ferrous ammonium sulfate (FeSO4·(NH4)2SO4·6H2O) C) Mohr's salt D) Potassium iodide (KI)

40. Which statement about the colors of chromium and manganese species is correct?

A) CrO4^2- is yellow, Cr2O7^2- is orange, MnO4^2- is green, MnO4^- is purple. B) CrO4^2- is orange, Cr2O7^2- is yellow, MnO4^2- is purple, MnO4^- is green. C) CrO4^2- is green, Cr2O7^2- is yellow, MnO4^2- is orange, MnO4^- is purple. D) CrO4^2- is purple, Cr2O7^2- is orange, MnO4^2- is yellow, MnO4^- is green.

41. The conversion of chromate to dichromate is an equilibrium process. What happens to the equilibrium when H+ ions are added?

A) The equilibrium shifts to the left (towards chromate) B) The equilibrium shifts to the right (towards dichromate) C) The equilibrium remains unchanged D) The reaction stops

42. Which of the following lanthanoids is known for its use in catalytic converters due to its ability to store and release oxygen?

A) Neodymium (Nd) B) Samarium (Sm) C) Cerium (Ce) D) Gadolinium (Gd)

43. What is the primary reason for the difficulty in separating lanthanoids from each other?

A) They have very different chemical properties. B) They have very similar chemical properties due to similar ionic radii and charge. C) They form very stable complexes with different ligands. D) Their atomic masses differ significantly.

44. Which of the following is a key component of nuclear fuel, primarily due to its fissile nature?

A) Thorium (Th) B) Protactinium (Pa) C) Uranium (U) D) Plutonium (Pu)

45. The f-block elements are also known as inner transition elements because:

A) Their f-orbitals are internal and shielded by outer d and s electrons. B) They transition between the d-block and p-block. C) They are found in the inner core of the Earth's crust. D) Their f-electrons are involved in forming the outermost electron shells.

46. Which of the following lanthanoid ions is colorless?

A) Ce^3+ B) Pr^3+ C) Eu^2+ D) Nd^3+

47. What is the oxidation state of Mn in the compound K2MnO4?

A) +2 B) +4 C) +6 D) +7

48. In the balanced redox reaction: Cr2O7^2- + 14H+ + 6e- → 2Cr^3+ + 7H2O, the oxidation state of Cr changes from:

A) +2 to +3 B) +3 to +6 C) +6 to +3 D) +7 to +3

49. Which of the following is NOT a property common to both lanthanoids and actinoids?

A) They are metals. B) They exhibit variable oxidation states. C) They are generally electropositive. D) They form colored ions.

Preparation properties and uses of K2Cr2O7 and KMnO4, lanthanoids and actinoids electronic configurations and oxidation states - Online Test

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