Write the formula for ammonium dichromate.
The correct answer and explanation is:
The formula for ammonium dichromate is (NH₄)₂Cr₂O₇.
Explanation:
Ammonium dichromate is a chemical compound made up of two ammonium ions (NH₄⁺) and one dichromate ion (Cr₂O₇²⁻).
- Ammonium ion (NH₄⁺): The ammonium ion is a positively charged polyatomic ion consisting of a nitrogen atom (N) bonded to four hydrogen atoms (H). It has a charge of +1. In ammonium dichromate, there are two ammonium ions, which gives a total positive charge of +2 (2 × +1).
- Dichromate ion (Cr₂O₇²⁻): The dichromate ion is a negatively charged polyatomic ion consisting of two chromium atoms (Cr) and seven oxygen atoms (O). The two chromium atoms are connected by an oxygen bridge, with each chromium atom being bonded to three oxygen atoms, and the remaining oxygen atoms are bonded to one chromium atom. The dichromate ion carries a charge of -2.
- Combining the ions: In order to create a neutral compound, the total positive charge must balance out the negative charge. Since the ammonium ion has a +1 charge, two ammonium ions (with a +2 charge) combine with one dichromate ion (with a -2 charge) to form ammonium dichromate. This results in a neutral compound.
Thus, the chemical formula for ammonium dichromate is written as (NH₄)₂Cr₂O₇, indicating that there are two ammonium ions for every dichromate ion. The compound is commonly used in laboratories and in demonstrations of chemical reactions, especially because of the dramatic exothermic reaction it undergoes when heated, producing nitrogen gas, water, and chromium oxide.