Here are some more MCQs focusing on the chemical properties of potassium permanganate (KMnO₄) and potassium dichromate (K₂Cr₂O₇):
1. In acidic medium, KMnO₄ oxidizes Fe²⁺ to:
a) Fe³⁺
b) Fe⁴⁺
c) Fe
d) FeO₄²⁻
Answer: a) Fe³⁺
2. In an acidic medium, KMnO₄ is reduced to:
a) Mn²⁺
b) Mn⁴⁺
c) MnO₂
d) MnO₄²⁻
Answer: a) Mn²⁺
3. What is the equivalent weight of KMnO₄ in acidic medium?
a) Molecular weight/1
b) Molecular weight/2
c) Molecular weight/3
d) Molecular weight/5
Answer: d) Molecular weight/5
4. Which of the following ions can be oxidized by K₂Cr₂O₇ in acidic medium?
a) Cl⁻
b) SO₄²⁻
c) Fe²⁺
d) Zn²⁺
Answer: c) Fe²⁺
5. The orange color of K₂Cr₂O₇ in acidic medium is due to:
a) Cr³⁺
b) Cr₂O₇²⁻
c) CrO₄²⁻
d) Cr⁶⁺
Answer: b) Cr₂O₇²⁻
6. Which of the following is reduced by K₂Cr₂O₇ in acidic medium?
a) Cl⁻ to Cl₂
b) Fe³⁺ to Fe²⁺
c) H₂S to S
d) Mn²⁺ to MnO₄⁻
Answer: c) H₂S to S
7. In acidic medium, the oxidation state of chromium in K₂Cr₂O₇ is reduced from:
a) +2 to +3
b) +6 to +3
c) +4 to +3
d) +5 to +4
Answer: b) +6 to +3
8. Which of the following reactions occurs when KMnO₄ is used in an alkaline medium?
a) MnO₄⁻ is reduced to Mn²⁺
b) MnO₄⁻ is reduced to MnO₂
c) MnO₄⁻ is reduced to Mn³⁺
d) MnO₄⁻ is reduced to Mn⁶⁺
Answer: b) MnO₂
9. In an alkaline medium, the final product of K₂Cr₂O₇ is:
a) Cr(OH)₃
b) Cr₂O₇²⁻
c) CrO₄²⁻
d) Cr²⁺
Answer: c) CrO₄²⁻
10. The oxidation state of manganese in KMnO₄ is:
a) +2
b) +4
c) +6
d) +7
Answer: d) +7
11. The oxidation state of chromium in K₂Cr₂O₇ is:
a) +3
b) +6
c) +5
d) +4
Answer: b) +6
12. In the reaction of K₂Cr₂O₇ with hydrogen peroxide in acidic medium, the products are:
a) CrO₄²⁻ and H₂O
b) Cr³⁺ and O₂
c) Cr₂O₇²⁻ and O₂
d) Cr²⁺ and H₂O
Answer: b) Cr³⁺ and O₂
13. Which of the following compounds is used as a self-indicator in redox titration?
a) K₂Cr₂O₇
b) KMnO₄
c) FeSO₄
d) KCl
Answer: b) KMnO₄
14. KMnO₄ can oxidize H₂S to:
a) SO₂
b) H₂O
c) Sulphur
d) SO₄²⁻
Answer: c) Sulphur
15. In neutral or alkaline medium, KMnO₄ oxidizes iodide ions (I⁻) to:
a) I₂
b) IO₄⁻
c) IO₃⁻
d) IO⁻
Answer: c) IO₃⁻
16. K₂Cr₂O₇ in an acidic medium oxidizes ethanol to:
a) Ethyl acetate
b) Acetone
c) Acetic acid
d) Formaldehyde
Answer: c) Acetic acid
17. Which of the following is a correct redox reaction involving K₂Cr₂O₇ in acidic medium?
a) K₂Cr₂O₇ → CrO₄²⁻
b) Cr₂O₇²⁻ → Cr³⁺
c) Cr³⁺ → CrO₄²⁻
d) Cr³⁺ → Cr₂O₇²⁻
Answer: b) Cr₂O₇²⁻ → Cr³⁺
18. In the reaction between KMnO₄ and oxalic acid in acidic medium, the product formed is:
a) Mn²⁺
b) MnO₂
c) Mn⁶⁺
d) Mn⁷⁺
Answer: a) Mn²⁺
19. KMnO₄ reacts with concentrated H₂SO₄ to produce:
a) Ozone
b) Oxygen
c) Mn₂O₇
d) MnO₂
Answer: c) Mn₂O₇
20. When K₂Cr₂O₇ is heated with NaOH, it forms:
a) Cr(OH)₃
b) Cr₂O₃
c) CrO₄²⁻
d) Cr³⁺
Answer: c) CrO₄²⁻
These questions focus on the oxidizing properties, reactions, and chemical behavior of KMnO₄ and K₂Cr₂O₇ in different mediums.
Here are 30 multiple-choice questions (MCQs) on the d and f block elements for CBSE Class 12:
1. Which of the following is a characteristic property of d-block elements?
a) High electronegativity
b) High melting and boiling points
c) Low density
d) Non-conductors of electricity
Answer: b) High melting and boiling points
2. Which of the following elements belongs to the f-block?
a) Iron
b) Uranium
c) Zinc
d) Copper
Answer: b) Uranium
3. Which of the following ions is colorless in aqueous solution?
a) Cu²⁺
b) Fe³⁺
c) Zn²⁺
d) Ni²⁺
Answer: c) Zn²⁺
4. The ability of transition metals to form complex compounds is due to:
a) High atomic size
b) Variable oxidation states
c) Large charge-to-radius ratio
d) Both b and c
Answer: d) Both b and c
5. Which of the following is an actinide element?
a) Thorium
b) Europium
c) Hafnium
d) Zirconium
Answer: a) Thorium
6. Which of the following d-block elements shows the maximum number of oxidation states?
a) Scandium
b) Manganese
c) Iron
d) Copper
Answer: b) Manganese
7. What is the electronic configuration of Cr³⁺?
a) [Ar] 3d³ 4s²
b) [Ar] 3d⁵
c) [Ar] 3d³
d) [Ar] 4s¹
Answer: c) [Ar] 3d³
8. Which of the following is paramagnetic?
a) Zn²⁺
b) Cu⁺
c) Fe³⁺
d) Sc³⁺
Answer: c) Fe³⁺
9. Lanthanide contraction is responsible for the similarity in atomic sizes of:
a) Lanthanides and actinides
b) 4d and 5d transition elements
c) 3d and 4d transition elements
d) 5d and 6d transition elements
Answer: b) 4d and 5d transition elements
10. Which of the following compounds exhibits the +3 oxidation state of iron?
a) FeCl₂
b) Fe₂O₃
c) FeSO₄
d) FeO
Answer: b) Fe₂O₃
11. The separation of lanthanides is difficult because they:
a) Have similar ionic sizes
b) Have similar chemical properties
c) Both a and b
d) None of the above
Answer: c) Both a and b
12. Which one of the following is the most stable oxidation state of actinides?
a) +2
b) +3
c) +4
d) +6
Answer: b) +3
13. Which of the following is an incorrect statement regarding f-block elements?
a) They show variable oxidation states
b) They are poor conductors of electricity
c) They have high melting points
d) They form colored ions
Answer: b) They are poor conductors of electricity
14. The general electronic configuration of lanthanides is:
a) [Xe] 4f¹–14 5d¹–10 6s²
b) [Xe] 4f¹–14 5d⁰–1 6s²
c) [Kr] 4d¹–10 5s²
d) [Rn] 5f¹–14 6d¹–10 7s²
Answer: b) [Xe] 4f¹–14 5d⁰–1 6s²
15. The most common oxidation state of transition metals is:
a) +1
b) +2
c) +3
d) +4
Answer: b) +2
16. The tendency of transition metals to form complexes is due to:
a) Small size of cations
b) Availability of d-orbitals
c) High charge-to-radius ratio
d) All of the above
Answer: d) All of the above
17. Which of the following is not a characteristic of transition elements?
a) High enthalpy of atomization
b) Formation of colored ions
c) High conductivity
d) All have magnetic properties
Answer: d) All have magnetic properties
18. Which of the following elements belongs to the 4d series?
a) Titanium
b) Ruthenium
c) Zinc
d) Chromium
Answer: b) Ruthenium
19. Actinides show a greater range of oxidation states than lanthanides due to:
a) Greater shielding effect
b) Lesser binding energy of 5f electrons
c) Higher atomic mass
d) Greater nuclear charge
Answer: b) Lesser binding energy of 5f electrons
20. Which of the following lanthanides is most abundant in nature?
a) Cerium
b) Neodymium
c) Samarium
d) Europium
Answer: a) Cerium
21. Which of the following is a characteristic property of actinides?
a) Low melting points
b) Formation of colored ions
c) Radioactivity
d) None of the above
Answer: c) Radioactivity
22. Transition metals form alloys because:
a) Their atoms are of similar size
b) They have high reactivity
c) They have variable valency
d) They have low melting points
Answer: a) Their atoms are of similar size
23. The element that does not exhibit variable oxidation states is:
a) Scandium
b) Copper
c) Zinc
d) Manganese
Answer: c) Zinc
24. Which of the following is a noble metal?
a) Iron
b) Platinum
c) Zinc
d) Nickel
Answer: b) Platinum
25. The oxidation state of chromium in potassium dichromate (K₂Cr₂O₇) is:
a) +2
b) +3
c) +5
d) +6
Answer: d) +6
26. Which of the following ions is colorless?
a) Cu²⁺
b) Fe³⁺
c) Zn²⁺
d) Ni²⁺
Answer: c) Zn²⁺
27. Which of the following elements has the highest atomic number?
a) Lanthanum
b) Yttrium
c) Actinium
d) Protactinium
Answer: d) Protactinium
28. The general electronic configuration of actinides is:
a) [Rn] 5f¹–14 6d⁰–1 7s²
b) [Xe] 4f¹–14 5d⁰–1 6s²
c) [Ar] 3d¹–10 4s²
d) [Kr] 4d¹–10 5s²
Answer: a) [Rn] 5f¹–14 6d⁰–1 7s²
29. Which of the following is the strongest oxidizing agent?
a) Fe²⁺
b) MnO₄⁻
c) Cr³⁺
d) Cu²⁺
Answer: b) MnO₄⁻
30. The color of potassium permanganate (KMnO₄) is due to:
a) d-d transition
b) Charge transfer
c) Absorption of red light
d) Ligand field splitting
Answer: b) Charge transfer
These questions cover a range of topics from the d and f block elements, including electronic configurations, oxidation states, properties, and trends in the periodic table.
