First Exercise (6 points)
Ammonia
Ammonia (NH3) is a colorless gas with very pungent odor that smells like urine. Often, it is sold as
ammonia-water solution. It is found in consumer products such as household cleaners. It is used to
prepare nitric acid. Both, nitric acid and ammonia are employed in the manufacture of fertilizers, such as
ammonium nitrate, which in turn in sued in the manufacture of explosives.
Ammonia is formed from two elements hydrogen and nitrogen, they are represented respectively, by the
atomic symbols 11 H and 147𝑁 .
1- a- Write the electron configuration of each of the given atoms.
b- Give the Lewis electron dot symbol for each atom.
2- Recopy the following table and complete it.
Element
Number of
Protons
Number of Neutrons
Number of
Electrons
Location of the
element in the
periodic table
Hydrogen
Nitrogen
3- Identify the type of the bond between each of the hydrogen atoms and the nitrogen atom in
ammonia molecule.
4- The synthesis reaction of ammonia is represented by the equation:
N 2  xH 2  yNH 3
- Determine x and y.
5- Based, on the passage, give the names of two compounds obtained from ammonia.
Second Exercise (7points)
Galvanic Cell
A device capable to convert chemical energy to electric energy is called Galvanic cell. When a strip of
magnesium is dipped into a beaker containing copper (II) sulfate solution, and oxidation – reduction
reaction occurs. The equation of the reaction is given as:
Mg + Cu2+ → Mg2+ + Cu
1- a- Identify the reducing agent in this reaction.
b- Write the reduction half -reaction of the above oxidation -reduction reaction.
2- It is required to construct the Galvanic cell (G), which when set to function its overall (cell) reaction
will be the reaction given above.
The Following Material Are available:
Zinc, copper, magnesium and silver strips
2 beakers
Solution containing copper (II) (Cu2+) ions
U-shaped salt bridge
Solution containing magnesium (Mg2+) ions
U-shaped copper wire
Solution containing zinc (Zn2+) ions
Connecting wires and alligator clips
Solution containing silver (Ag+) ions
A voltmeter
a- List from the available materials those that are the essential components of the Galvanic cell (G) to be
constructed.
b- Describe how to construct the Galvanic cell (G).
c- Sketch and label the constructed Galvanic cell (G), which is set to function and show the direction of
the electron flow.
d- Write the half - reaction the occurs at the anode.
Third Exercise (7 points)
Hsloalkanes (Halogenated Derivatives of Alkanes)
Several alkanes are used to prepare haloalkanes, such as halogenated derivatives of methaen and ethane.
Haloalkanes have found wide uses. For example, dichloromethane is used as solvent, trichloromethane
is used as anesthetic and 1,1, 1- trichloroethane is used as a solvent for correction-pen (Tip-Ex).
A pure substance is in the liquid state when its temperature is between its normal freezing point and its
normal boiling point. The normal boiling point and normal freezing point of several unbranched
straight-chain alkanes are given in the table below:
Temperature
0
C
Boiling point
Freezing point
Methane
Propane
-164
-180
-42
-190
Butane
0
-138
Pentane
Hexane
Octane
36
-130
69
-95
126
-57
1) a- Justify which of the two alkanes, propane and butane, is liquid at -300C, and which of the two
alkanes, butane and pentane, is gas at 270C.
b- Deduce from the table, how the boiling point of the given alkanes changes with the change in the
number of carbon atoms in their molecules.
2) Two compounds (A) and (B) respectively have the structural formulas (I) and (II) given below:
a- Give the (IUPAC) name of compound (A).
b- Specify whether compounds (A) and (B) are isomers.
3) Chloromethane is derived from the reaction of methane with chlorine.
- Write the equation of the reaction that takes place.
4) Based on the passage, give two uses of chlorinated derivatives of methane.