Answer: B. trigonal planar
Explanation:
Valence Shell Electron Pair Repulsion Theory (VSEPR) is a model to predict the geometry of the atoms making up a molecule where atoms are arranged such that the forces of repulsion are minimum.
If a central atom is bound to three electron domains ,the number of electron pairs is 3, that means the hybridization will be 
and the electronic geometry of the molecule will be trigonal planar as the electron pairs will repel each other and attain a position which is most stable.
Example: 
with 3 electron domains has trigonal planar geometry.
I don't know but look on the internet or use a calculator
Answer:
CaS
Explanation:
calcium is Ca2+ and sulfur is S2- because the charges are equal you only need one of each atom, so the answer is CaS
739 is the number of atoms of O in 92.3 moles of Cr3(PO4)2.
Explanation:
Molecular formula given is = Cr3(PO4)2
number of moles of the compound is 92.3 moles
number of 0 atoms in 92.3 moles =?
From the chemical formula 1 mole of the compound has 8 atoms of oxygen
So, it can be written as
1 mole Cr3(PO4)2 has 8 atoms of oxygen
92.3 moles of Cr3(PO4)2 has x atoms of oxygen
= 
x = 8 x 92.3
x = 738.4 atoms
There will be 739 oxygen atoms in the 92.3 moles of Cr3(PO4)2.
