d and f BLOCK ELEMENTS

What is the main reason potassium dichromate can be used as a primary standard?

• Its bright color
• Its low cost
• Its high purity and stability
• Its strong smell

In the half-reaction 6 Fe^2+ -> 6Fe^3+ + 6 e–, what role does Fe^2+ play?

• It acts as an oxidizing agent
• It acts as a reducing agent
• It is reduced
• It remains unchanged

Which of the following equations represents the conversion of chromate ions to dichromate ions?

• Cr2O7^2- + 2 OH- -> 2 CrO4^2- + H2O
• CrO4^2- + H2O -> Cr2O7^2- + H2
• 2 CrO4^2- + 2H+ -> Cr2O7^2- + H2O
• Cr2O7^2- -> 2 CrO4^2- + H2

What is the oxidation state of chromium in the dichromate ion (Cr2O7^2-)?

• +3
• +6
• +7
• 0

In the equilibrium reaction 2 CrO4^2- + 2H+ <-> Cr2O7^2- + H2O, what would happen if acid (H+) is added to the solution?

• The equilibrium would shift to form more chromate (CrO4^2-)
• The equilibrium position would remain unchanged
• The equilibrium would shift to form more dichromate (Cr2O7^2-)
• It is impossible to determine