Chemistry test 5?

[Razor light]

17.A certain hard substance that is very hard, has a high meltin point, and is nonconducting unless melted is most likely to be:
a I2
B NaCl
c CO2
d H2O
e Cu

18.Which of the following statements is false?
a Diamond is covalent crystal molecular
b The size of the unit cell of Li ans Cs is the same
c Molecular crystals usually have low mwlting points
d metallic crystals are usually good electric conductors
e all of the following statements are true

19.At normal atmospheric pressure and a temperature of 0C which phase(s) of H2O can exist ?
a ice and water
b ice and water vapor
c water only
d water vapor only
e ice only

20.Assume 12,500J of energy is added to 2.0 moles (36grams) of H2O as an ice sample 0C. The molar heat of fusion is 6.02kJ/mol.The specific heat of liquid water is 4.18J/mol K. The molar heat of vaporization is 40.6kJ/mol.The resulting conatains the following?
a only ice
b ice and water
c only water
d water and vapor
e only water vapor