Boiling point is highly dependent on the intermolecular forces of a compound. Compounds with stronger intermolecular forces, larger masses, and less branching will have higher boiling points.

Compounds II and III only exhibit intermolecular London dispersion forces, so they would be the two lowest boiling compounds (weakest intermolecular forces). Because compound III has more branching, these London dispersion forces would be weaker, resulting in a lower boiling point than compound II.

III < II

Compounds I and IV would be higher boiling point compounds because of additional hydrogen bonding (strong intermolecular forces). Compound IV would be the highest boiling because the hydroxy group and carboxylic acid group could BOTH participate in intermolecular hydrogen bonding. In addition, compound IV is more polar (more polarized carbon-oxygen bonds), resulting in greater dipole-dipole attraction as well.

III < II < I < IV

Intermolecular forces become relevant when there are partial charge differences between atoms in the molecule, generating polarized bonds. In order for this to happen, the two bonded atoms must have different electronegativities such that one atom pulls the electrons in the bond closer to it.

In liquid bromine , the two bromine atoms have the same electronegativity, so there is no unequal sharing of electrons. As a result, only London dispersion forces are found between bromine molecules.

Ethanol and ammonia are capable of hydrogen bonding, while acetone is capable of dipole-dipole interactions due to the polarized carbon-oxygen bond.

Water is the most polar solvent. Polar molecules contain bonds that have charges that are opposite in charge with high electronegativity differences. The oxygen atom in water draws electrons away from the hydrogen atoms causing the oxygen to be more negatively charged and hydrogen atoms to be more positively charged. Water would not be polar without its bent geometry which allows it to have a non zero dipole moment (1.85D), making it a polar molecule. The polarity of water is essential for life as we know it.

Two solvents are miscible if after mixing them, they form a homogeneous mixture. The saying, like dissolves like, is an explanation of why benzene which is non polar will dissolve in a non polar solvent such as pentane. Polar molecules are soluble in polar solvents. For example, water is miscible in alcohols. Ionic substances such as common table salt which is composed of sodium chloride dissolve in water but do not dissolve to any great extent in most organic solvents which are non-polar. If we were to mix the benzene solution with water, we will find that they are not miscible and form a heterogenous mixture. Methanol , is the only polar solvent in the options given and is miscible with water.

When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.  

Sodium and chlorine form an ionic bond, meaning that one atom will donate an electron and the other will receive it. This gives each atom a charge. Chlorine has seven valence electrons, while sodium has one valence electron. For each atom to arrive at an octet, sodium will need to lose one electron and chlorine will need to gain one electron. This would give chlorine a negative charge, and sodium a positive charge.

Thus, the answer is a sodium with a positive charge (due to one lost electron) and a chlorine with eight electrons and a negative charge (due to one electron gained). 

When drawing a Lewis dot structure, we are always trying to reach an electron count where all atoms involved are stable and (usually) have full octets. We are also trying to estabilsh a structure in which we have the smallest formal charge possible. The general rule is first to draw out all of the elements involved and their valence electrons, then start piecing them together trying to reduce the formal charge and get all elements involved to an octet. There are a couple exceptions to the octet rule.

In this case, boron actually has an incomplete octet. Though there are resonance forms in which boron has a full octet, when you calculate the formal charge of these configurations it will not be zero.

According to VSEPR theory, atoms will orient themselves in order to be as far away from neighboring atoms as possible in a molecule. This theory helps predict the geometry that molecules will take, as well as the bond angles between atoms.

 is formed by a central carbon bound to two adjacent oxygen atoms. To maximize the distance between the oxygen atoms, they will align at an angle of 180 degrees, creating a linear shape.

All of the other given moleules will have bond angles less than 180 degrees.

Recall the following relationships between geometry and number of pairs of electrons on the central atom.

2: linear

3: trigonal planar

4: tetrahedral

5: trigonal bipyriamidal

6: octahedral

To visualize the geometry, we need to think of how many electron pairs are on the central atom. Drawing Lewis dot diagrams may be helpful here. None of the answer choices has lone central electron pairs, with the exception of water, so the number of atoms bound to the central atom is the same as the number of central electron pairs.

The only one that does not match up with the correct geometry is SF₆, which is actually octahedral since it has six central electron pairs. In a water molecule, the central oxygen has six valence electrons, plus one from each bond with hydrogen, for a total of eight central electrons and four central electron pairs. So, this geometry is a variation on the tetrahedral form (bent), in which two central electron pairs are not bound.

The trigonal pyramidal geometry is implemented by molecules in which the central atom has three atoms and a lone pair attached.  has three hydrogens attached to the central phosphorus as well as a lone pair, which can be determined by drawing the Lewis structure of the molecule. As a result, it has trigonal pyramidal geometry.

 is trigonal planar.  is tetrahedral.  is octahedral.

Electronic and molecular geometries are only the same when there are no lone pairs around the central atom in the molecule.  is the only given option that does not have a lone pair on the central atom, so the electronic geometry is the same as the molecular geometry (in this case, tetrahedral).