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Chemical Bonding: Melting Point

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, 25oC) 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 682oC and a solubility of 3.67 kg/kg H2O at 25oC. 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?

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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, 25oC) 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.

When we move down the group, size f halogen atom increases, and therefore, the bond length of Na-X increase down the group(X is halogen). Therefore, we can see that bond length increases down the group and hence, bond is easy to break. Therefore, melting point decreases down the group from NaF to NaI.

b) Explain the increasing solubility in the same order.

When we move down from NaF to NaI, the ionic character of the molecule increase that is NaI is most ionic. Therefore, due to ...

Solution Summary

This solution answers several chemistry questions, addressing melting point, solubility, ionic bonds and STP.

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