To determine the correct formula for diarsenic pentoxide, we should look at the chemical composition of the compound. The name "diarsenic pentoxide" provides an important clue:
1. "Diarsenic" indicates that there are 2 atoms of arsenic (As) in the compound.
2. "Pentoxide" indicates that there are 5 atoms of oxygen (O) in the compound. The prefix "penta-" means 5.
Combining these pieces of information, the chemical formula for diarsenic pentoxide must consist of 2 arsenic atoms and 5 oxygen atoms.
Given the options:
1. [tex]$Ar_2O_5$[/tex]: This formula suggests it has 2 argon atoms and 5 oxygen atoms, which is incorrect because argon (Ar) is a noble gas and does not form such compounds.
2. [tex]$As_5O_2$[/tex]: This formula suggests it has 5 arsenic atoms and 2 oxygen atoms, which is not consistent with the name "diarsenic pentoxide."
3. [tex]$As_2O_5$[/tex]: This formula suggests it has 2 arsenic atoms and 5 oxygen atoms, which correctly matches the composition indicated by "diarsenic pentoxide."
4. 2As5O: This formula lacks proper subscripts for atoms and suggests an incorrect ratio of atoms.
Therefore, the correct formula for diarsenic pentoxide is [tex]$As_2O_5$[/tex].
