1. C. molybdate, MoO42-, D. permanganate, MnO4-
QUESTION:
Which of the following polyatomic ions is not paired with its correct formula? A. chromate, CrO42-, B. dichromate, Cr2O82-
C. molybdate, MoO42-, D. permanganate, MnO4-
Dichromate is Cr2O72-.
Names and formulas of polyatomic ions are trivial information --- just memorize.
These are the most common oxoanions with transition metals.
SCRIPT:
Which of the following polyatomic ions is not paired with its correct formula? Chromate… dichromate… molybdate… or permanganate….
PAUSE CLICK The correct answer is B. Dichromate is Cr2O7 with a –2 charge. Not Cr2O8 with a –2 charge.
CROSS OUT 8 in choice B.
Names and formulas of polyatomic ions are trivial information. In other words, you just need to memorize them as part of the basic vocabulary of Chemistry. Whether or not your teacher requires you to memorize them, it’s a good idea to just memorize them.
CLICK
There are several other oxoanions that can be formed between the transition metals given here and oxygen.
The ions given in this question are four of the most common ones you’ll encounter.
PAUSE
END RECORDING

2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08