d and f BLOCK ELEMENTS

What is a major industrial use of potassium dichromate (K2Cr2O7)?

• As a reducing agent in metallurgy
• As a catalyst in polymerization
• As an oxidant in the preparation of azo compounds
• As a dehydrating agent in organic synthesis

Which of the following reactions represents the disproportionation of manganese(VI) in acidic solution?

• MnO4 – + 8 H+ + 5 e– → Mn2+ + 4 H2O
• 2 MnO4 – + 6 H+ + 5 H2O2 → 2 Mn2+ + 5 O2 + 8 H2O
• 3 MnO4 2– + 4 H+ → 2 MnO4 – + MnO2 + 2H2O
• MnO2 + 4 HCl → MnCl2 + Cl2 + 2 H2O

What is the main acidic oxoanion formed when V2O5 reacts with an alkali?

• VO2 +
• VO4 3–
• V2O4 2-
• VO3 -

Which of the following transition metal oxides is described as amphoteric, though mainly acidic?

• Mn2O7
• CrO3
• V2O5
• Sc2O3

What type of acid does CrO3 give when it reacts with water?

• HCrO2
• H2CrO4 and H2Cr2O7
• H3CrO3
• Cr(OH)3