Final answer:
The total number of electron domains in a molecule with the molecular formula AX5 is 5, representing each bond between the central atom 'A' and the five 'X' atoms. The molecular weight of 'X' is not determinable with this information, and the chemical formula is vital for calculating moles of atoms within a compound.
Step-by-step explanation:
The total number of electron domains in a molecule with the molecular formula AX5 is 5. This is because the molecule has five regions of electron density, which include any place around a central atom where electrons are likely to be found. These regions are attractions due to bonds with other atoms: each AX5 molecule contains a central atom 'A' bonded to five 'X' atoms with no lone pairs of electrons. For example, in the molecule PF5, phosphorus (P) is the central atom and it forms five bonds with fluorine (F) atoms, resulting in five electron domains.
The molecular weight of 'X' cannot be determined from the information provided about electron domains, as it requires knowing the specific element 'X' refers to and its atomic mass.
Knowing the formula for a molecule is essential when calculating the number of moles of an atom because it tells you the ratio of different atoms in the molecule. For instance, in MgF2, knowing that there are two fluorine atoms for every magnesium atom allows us to calculate that in 5.6×1022 molecules of MgF2, there would be 11.2×1022 atoms of fluorine, because each molecule contains 2 atoms of fluorine.