There are 18. In each molecule of Fe(NO3)2 there are 6 oxygen atoms because you have 2 nitrate (NO3) components which each contain 3 oxygen atoms. 2 x 3 = 6. Because you have 3 molecules of Fe(NO3)2, you need to multiply 6 by 3, which gives you 18 oxygen atoms.
Answer: 300 K
Explanation:
Charles' Law: This law states that volume is directly proportional to the temperature of the gas at constant pressure and number of moles.
(At constant pressure and number of moles)

Given : V= 6.0 L
k= 0.020 L/K
T=?


Thus temperature of the gas is 300 K.
Answer:
A bonding that occurs between high electronegative atoms such are N, F, O and H atoms, is called a hydrogen bond. Hydrogen bond is a very strong bond. (C)
If hydrogen bonds are not formed between H atoms and N, F, O atom, then the atoms interact through dispersion forces (also known as london dispersion forces). Dispersion forces are weak and they are temporary forces formed by overlapping of orbitals. (B)