Mount Alvernia High School
CAPE Chemistry Unit 1
Worksheet #2: Forces of Attraction
1. From the information in the table below, say what you can about the chemical bonds in A,B,C,D
and E.
Substance
A
State
Liquid
Melting point (0C)
-60
B
Solid
890
C
Solid
720
D
Solid
85
E
Gas
-100
Electrical conductivity
Does not conduct
electricity
Conducts electricity
when molten
Does not conduct
electricity when
molten
Does not conduct
electricity when
molten
Does not conduct
electricity
A-This is a covalent compound which has covalent bonds. This is done between nonmetals and it
involves the sharing of electrons. This was indicated through the fact that this substance has a low melting
point and does not conduct electricity.This is because the molecules are held together by a weak
intermolecular force which require little energy to break. It doesn't conduct electricity because there is
no free moving ions or electrons.
B- this is an ionic compound which has an ionic bond. This is done between a metal and a nonmetal, where
the metal transfers an electron to a nonmetal.An electrostatic force constitutes the bond between the
oppositely charged ions. This substance does not conduct electricity when molten because the ions are
only mobile when the substance is in a molten state.
C-This is a giant covalent structure which is bonded together by covalent bonds. They do not really contain
intermolecular forces. They are simply held together by covalent bonds between the atoms of the
structure.Due to this it requires high amounts of energy to break the bond and there are no charged
particles in this substance for it to conduct electricity.
D- this is a covalent compound which has covalent bonds between the atoms of the molecule and
intermolecular forces between molecules. This substance has a higher melting point compared to other
covalent compounds such as substance A because the more intermolecular forces that a molecule has the
stronger the attraction resulting in more energy being needed to break the bonds. This is so because the
atoms / molecules are bigger.
CAPE CHEM U1
K. Brown
E- this is another covalent compound with covalent bonds between the atoms of the molecule and
intermolecular forces between molecules. The intermolecular forces in the substance are so weak that
the molecules are so far apart that the substance is a gas. The attraction between the molecules are
weak.
2. A.
The boiling points of three gases ammonia, hydrogen chloride and carbon dioxide are
given below:
Gas
Ammonia
Hydrogen chloride
Carbon dioxide
Mr
17
36.5
44
b.p./ 0C
-33
-85
-78
Describe the intramolecular and intermolecular bonding in each of the above
compounds, relating the bonding the boiling point where appropriate [6
Ammonia- Ammonia is a polar gas with intermolecular hydrogen bonds. These bonds
are stronger, being harder to break, resulting in ammonia having the highest boiling
point of the three. The hydrogen bonds in ammonia are less in abundance than they
are in water. There are less bonds needed to be broken , less energy being required
resulting in it having a lower boiling point than water. There are also covalent bonds as
intramolecular bonds which are very strong but are not required to be broken for the
substance to boil. it is the intermolecular bonds that are broken when boiling occurs.
Hydrogen Chloride- The intramolecular bonds in Hydrogen Chloride are Covalent Bonds.
It is a very polar molecule resulting in it having dipole- dipole interactions as its
intermolecular bond. Due to this being a weak force the boiling point of hydrogen
chloride is very low.
Carbon Dioxide-Carbon Dioxide is a nonpolar gas with intramolecular Covalent bonds
and dipole dipole induced Intermolecular bonds which makes the compound have an
extremely low boiling point because this type of bond is weak, being very easy to break.
CAPE CHEM U1
K. Brown
Illustrate the intermolecular bonding present in ammonia and hydrogen chloride. [2]
Use dot and cross diagram to show the arrangement of electrons in the CO2 molecule. [2]
B. What types of intermolecular forces operate in these compounds:
i.
HBr (g)Dipole–Dipole interactions
ii.
Br2(g)-dipole–induced dipole interactions
iii.
ICl (g)-Dipole dipole forces
iv.
c.
HF (l)-hydrogen bonds
Identify the following molecules as polar or non-polar:
i.
BF3-non polar
ii.
CH3Cl-polar
iii.
CO2-nonpolar
iv.
NH3-polar
3. (a) Magnesium oxide, diamond, aluminum are all solids. Using structure and bonding explain
the differences, if any, among these solids in terms of:
●
●
●
Melting point
Electrical Conductivity
Solubility
Magnesium oxide is an ionic substance having ionic bonds , Diamond a giant
covalent structure with solely covalent bonds and aluminum a metal with metallic
bonds.The substance with the highest melting point is the Magnesium oxide and
this is because of its ionic bond that is much stronger than the covalent bond and
CAPE CHEM U1
K. Brown
the metallic bond. Magnesium oxide conducts electricity when molten because in
this state it allows the charged particles (ions) to move allowing for the conduction
of electricity. Diamond does not conduct electricity whether molten or solid
because it has no charged particles present. It has no free electrons. The aluminum
conducts electricity whether molten or solid. The metallic bond in it allows for the
free moving of electrons in any state it is in. Magnesium oxide is not soluble . The
attraction in magnesium oxide is so tight that water cannot overcome this. Diamond
is also not soluble in water because of the same reason as magnesium oxide.
Aluminum is soluble in water but it does not readily dissolve because of the
formation of a thin but protective layer of aluminum oxide that forms, preventing
any further corrosion.
(b)
Using structure and boiling point explain why iodine
●
Is brittle- Iodine is brittle because in its structure, strong electrostatic attraction
holds the cations and anions in a distinct position in a crystal lattice.This is the
covalent bonds holding the atoms of the molecule together.Due to iodine being
a large atom , there are a lot of van der waals between the molecules resulting
in the bonds being harder to break. The molecules of iodine are held close
together allowing for it to have a solid crystalline structure but due to it having
weak van der waals forces when you try to shape this structure it breaks away.
●
Does not conduct electricity- Iodine is a nonmetal and most nonmetals are bad
conductors of electricity as they do not contain mobile electrons since each
iodine molecule comprises two iodine atoms joined by a covalent bond.
●
Iodine vaporizes very easily- Iodine vaporizes very easily because of the weak
van der waals forces that exist between the molecules. When heated to its
boiling point of 184.3C the weak van der waals forces are easily overcome and
the molecules break into a gas form.
CAPE CHEM U1
K. Brown