Explain why graphite is soft and has a high melting point

Question

Questions:

1. Consider the following data: expect a BeF₂ molecule to be linear but an SF₂ molecule to be angular.

                                                Solubility in Water                  Melting

                                                (kg/kg H₂O, 25^oC)                  Point (^oC)

NaF                                         0.042                                       988

NaCl                                        0.357                                       801

NaBr                                       1.16                                         755

Nai                                          1.84                                         651

a) Explain the decreasing melting point from NaF to Nai.

b) Explain the increasing solubility in the same order.

c) Cesium fluoride has a melting point of 682^oC and a solubility of 3.67 kg/kg H₂O at 25^oC. Explain the difference between the properties of CsF and NaF.

2. What test would determine whether a solid substance contains ionic bonds?

3. a) Explain why graphite is soft and has a high melting point.

b) Explain why diamond is hard and has a high melting point.

c) Why is diamond a poor conductor of an electric current and graphite a good conductor?

4. Answer the following questions using the information in the table.

Element	Melting point (°C)	Boiling point (°C)	Molar volume at STP (L)
A	-189	-186	22.4
B	-100	-35	22.4
C	-7	58	2.6 x 10-2
D	30	2240	1.2 x 10-2
E	44	280	1.7 x 10-2
F	660	2450	1.0 x 10-2
G	3410	5930	1.0 x 10-2

a) Which elements are likely to be metals?

b) Which elements are gases at STP?

c) Which element is most likely to be a non-metallic solid?

d) Which elements are likely to conduct well in the solid form?