Which are correct formulas for ionic compounds? for those that are not correct, give the correct formula and justify your answer

Read more on link

a. AlCl is incorrect because Al has a +3 charge while Cl only has a -1 charge. The correct formula would be AlCl₃. This balances the charges.

b. Na₃SO₄ is incorrect because Na has a charge of +1 and there are three of them so its +3 and SO₄ has a charge of -2. The correct formula would be Na₂SO₄. This balances the charges.

c. BaOH₂ is incorrect because the polyatomic ion OH would not be written that way. It would be written like this Ba(OH)₂. Writing it like BaOH₂ gives the impression that instead of having 2 OH it has 2 H and 1 O.

d. Fe₂O is incorrect because Fe either has a +2 charge or +3 charge while O has a -2 charge. Possible correct answers could be FeO (iron (II) oxide) or Fe₂O₃ (iron (III) oxide).

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.