Preparation properties and uses of K2Cr2O7 and KMnO4, lanthanoids and actinoids electronic configurations and oxidation states - One Line Questions

1. What is the general electronic configuration of lanthanoids? — [Xe] 4f^1-14 5d^0-1 6s^2
2. What is the general electronic configuration of actinoids? — [Xe] 5f^1-14 6d^0-1 7s^2
3. The most common oxidation state exhibited by lanthanoids is: — +3
4. 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? — All of the above
5. What is the oxidation state of Mn in the compound K2MnO4? — +6
6. In the balanced redox reaction: Cr2O7^2- + 14H+ + 6e- → 2Cr^3+ + 7H2O, the oxidation state of Cr changes from: — +6 to +3
7. What is the change in oxidation state of chromium when K2Cr2O7 acts as an oxidizing agent in acidic solution? — +6 to +3
8. What is the change in oxidation state of manganese when KMnO4 acts as an oxidizing agent in acidic solution? — +7 to +2
9. Which reaction demonstrates the oxidizing property of KMnO4 in neutral/faintly alkaline medium? — MnO4^- + 2H2O + 3e- → MnO2 + 4OH-
10. Lanthanoids are a series of elements characterized by the filling of which subshell? — 4f
11. Actinoids are a series of elements characterized by the filling of which subshell? — 5f
12. In the preparation of potassium dichromate, chromite ore is first converted to sodium chromate. What is the chemical equation for this step? — 4FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2
13. Which element is considered the first member of the actinoid series? — Actinium (Ac)
14. Which of the following is a common use of potassium dichromate in laboratories? — As a primary standard in redox titrations
15. Potassium permanganate is widely used as an oxidizing agent. Which of the following is a significant application of KMnO4? — All of the above
16. Which of the following lanthanoid ions is colorless? — Eu^2+
17. Which of the following reactions best illustrates the oxidizing property of K2Cr2O7 in acidic medium? — Cr2O7^2- + 6Fe^2+ + 14H+ → 2Cr^3+ + 6Fe^3+ + 7H2O
18. 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? — Cr^3+
19. Which statement about the colors of chromium and manganese species is correct? — CrO4^2- is yellow, Cr2O7^2- is orange, MnO4^2- is green, MnO4^- is purple.
20. What is the primary method for the industrial preparation of potassium dichromate (K2Cr2O7)? — Fusion of chromite ore (FeCr2O4) with sodium carbonate and limestone in the presence of air
21. The conversion of potassium manganate (K2MnO4) to potassium permanganate (KMnO4) can be achieved by oxidation. Which method is commonly used? — All of the above
22. Which of the following lanthanoids commonly exhibits an oxidation state of +4 in addition to +3? — Cerium (Ce)
23. How is potassium permanganate (KMnO4) typically prepared industrially from pyrolusite ore (MnO2)? — Fusion of MnO2 with potassium hydroxide in the presence of air or oxygen
24. Due to the actinoid contraction, the atomic radii of elements following the actinoid series are expected to: — Show a less pronounced decrease compared to lanthanoid contraction
25. What is the primary characteristic that leads to the similar chemical properties of lanthanoids? — Similar electronic configurations of valence shells (6s^2)
26. 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? — Involvement of 6d electrons
27. Uranium (U, Z=92) exhibits several oxidation states, including +3, +4, +5, and +6. This variability is characteristic of: — Actinoids
28. Which statement accurately compares lanthanoids and actinoids regarding their electronic configurations? — Lanthanoids involve filling of 4f orbitals, while actinoids involve filling of 5f orbitals.
29. 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? —
30. Which element marks the beginning of the lanthanoid series? — Lanthanum (La)
31. Actinoids are generally more reactive than lanthanoids. What is a contributing factor to this difference in reactivity? — Lower ionization enthalpies of actinoids
32. In neutral or faintly alkaline solution, MnO4^- is reduced to which species? — MnO2
33. The oxidizing strength of KMnO4 varies with pH. In acidic medium, MnO4^- is reduced to which species? — Mn^2+
34. Potassium dichromate is used in various applications. Which of the following is NOT a typical use of K2Cr2O7? — Production of fertilizers
35. Which of the following lanthanoids is known for its use in catalytic converters due to its ability to store and release oxygen? — Cerium (Ce)
36. 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: — Half-filled 4f subshell
37. 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: — Completely filled 4f subshell
38. Lanthanoid contraction refers to the gradual decrease in atomic and ionic radii across the lanthanoid series. What is the main reason for this contraction? — Poor shielding of the nuclear charge by 4f electrons
39. 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? — Potassium manganate (K2MnO4)
40. Potassium permanganate solution is often standardized before use in titrations. What is a common substance used for its standardization? — Sodium oxalate (Na2C2O4)
41. The conversion of chromate to dichromate is an equilibrium process. What happens to the equilibrium when H+ ions are added? — The equilibrium shifts to the right (towards dichromate)
42. The f-block elements are also known as inner transition elements because: — Their f-orbitals are internal and shielded by outer d and s electrons.
43. Which of the following is NOT a property common to both lanthanoids and actinoids? — They exhibit variable oxidation states.
44. What is the primary reason for the difficulty in separating lanthanoids from each other? — They have very similar chemical properties due to similar ionic radii and charge.
45. Which of the following is a key component of nuclear fuel, primarily due to its fissile nature? — Uranium (U)
46. 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? — To convert chromate ions into dichromate ions by protonation
47. What is the purpose of adding sulfuric acid to sodium dichromate solution to obtain potassium dichromate? — To precipitate potassium dichromate due to its lower solubility compared to sodium dichromate
48. All actinoids are radioactive. This is a key difference from lanthanoids, where only promethium (Pm) is radioactive. — True, all actinoids are radioactive
49. Potassium permanganate (KMnO4) is a powerful oxidizing agent. What is the color of the permanganate ion (MnO4^-)? — Purple
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