helpppppppppp pleaseeeeeeeeeeeeeee?

1. An unidentified element crystallizes in a face-centred cubic lattice. The edge length of the unit cell is 446 pm/ The density of the solid is found to be 1.51g/cm^3. What is the molar mass of the elemnet, in g /mol?

2. What is the enthalpy change, in Kj/mol, for the process below?

Ca^2+ (g) + 2Cl^- (g) --> CaCl2 (s)

Data (in kJ/mol):

Enthalpy of sublimation of Ca(s): 178

Bond dissociation energy of Cl2(g): 244

Ionization energies (1st, 2nd, 3rd) of Ca(g): 590; 1,145; 4,912

Ionization energies (1st, 2nd, 3rd) of Cl(g): 1,252; 2,297; 3,822

First electron affinity of Cl(g): -349

Standard enthalpy of formation for CaCl2(s): -796

3. Two elements, X and Y, form a crystalline material. The crystal lattice of this material can be described as follows. The X atoms form a cubic closest packed structure and the Y atoms occupy half of the tetrahedral sites in the lattice of X atoms.

The empirical formula of the solid is: X ____ Y ____

4. Which of the following compounds has the lowest boiling point?

(a) H2O

(b) CH3COOH

(c) CH3CH2CH2NH2

(d) H3C-O-CH2CH3

(e) CH3CH2CH2OH

please explain in steps.