Question

In the dichromate dianion ______.

Options

• 4 Cr-O bonds are equivalent.

• 6 Cr-O bonds are equivalent.

• all Cr-O bonds are equivalent.

• all Cr-O bonds are non-equivalent.

Answer 1

In the dichromate dianion 6 Cr-O bonds are equivalent.

Explanation:

The dichromate ion \[\ce{(Cr2O^{2-}_7)}\] contains two chromium atoms joined by a C-O-Cr bridge. Each chromium is surrounded by four oxygen atoms. Three terminal (double-bonded) oxygens, one bridging oxygen. So, 6 terminal Cr-O bonds are equivalent in length and strength. The Cr-O-Cr bridge contains 2 non-equivalent Cr-O bonds due to the bridging nature.