Electronic Configuration, Importance of Periodic Table, Water Molecule Shape, Molarity Calculations, Organic Compound Purification

This article covers electronic configuration of elements, importance of periodic table, shape of water molecule, molarity calculations and organic compound purification.

1. Write the full electronic configuration for the following:
Phosphorus : 1s2 2s2 2p6 3s2 3p3
Sodium 1s22s22p63s1
Calcium 1s² 2s² 2p⁶ 3s² 3p⁶4s²
Krypton 1s2 2s2p6 3s2p6d10 4s2p6
Bromine 1s22s22p63s23p63d104s24p5
Carbon 1s 2 2s 2 2p 2
Nitrogen 1s2, 2s2, 2p2, 3s1
Fluorine 1s22s22p5
Hydrogen 1s1
Silicon 1s2 2s2 2p6
Q U E S T I O N 2
1. Write a brief note on the importance of the Periodic table, and indicate how it would be used
by a chemist, giving examples of where you may have used it.
Importance of periodic table
i. identification
The periodic table of the elements describes the atomic structure of all elements that are
known to mankind. For instance, by looking at the periodic table, a person can find out
how many electrons the element has and how much it weighs. Each element has its own
separate set of such data; no two elements are the same. Thus, if someone is uncertain
what matter he has, he can look at the atomic structure of the material, compare it to
the information in the periodic table, and identify the material by matching it to the
element on the table with the same data.
ii. Families and Periods of the Elements
The elements in the periodic table are grouped in particular families and periods
(vertical and horizontal rows). The elements in each family or period have similar or
dissimilar characteristics. The table thus is a quick reference as to what elements may
behave the same chemically or which may have similar weights or atomic structures.
iii. Property-Based Experiments
The information contained in the periodic table (such as atomic weight and what
elements are similar) lets scientists know how the elements are put together atomically
and how they will behave. Once scientists understand this data, they can apply it in
experiments. These experiments can be something as simple as combining hydrogen and
oxygen to make water, or they can be as dramatic as making a hydrogen bomb.
iv. Classification of the Elements
The periodic table can be used to identify the matter already discovered by mankind.
However, if new matter is discovered, then the atomic structure of the new matter can
be compared to the elements in the table in order to classify the new material. Scientists

can use the data in the table to figure out how the new matter may behave or what
elements to which the new matter may be similar through this comparison.
The table is useful for modern students and chemist because it helps predict the types of chemical
reactions that are likely for an element. It may be used in classrooms to study chemical reactions
by the students. It may as well be applied where some researches are being conducted to further
check on given element.
Q U E S T I O N 3
Write a short note on the shape of the Water molecule
The shape of water molecules is bent or angular molecules have a non-linear shape. For example,
water (H2O), which has an angle of about 105°. A water molecule has two pairs of bonded
electrons and two unshared lone pairs. Each molecule is electrically neutral but polar, with the
center of positive and negative charges located in different places. Each hydrogen atom has a
nucleus consisting of a single positively-charged proton surrounded by a 'cloud' of a single
negatively-charged electron and the oxygen atom has a nucleus consisting of a eight positively-
charged protons and eight uncharged neutrons surrounded by a 'cloud' of a eight negatively-
charged electrons. On forming the molecule, the ten electrons pair up into five 'orbitals', one pair
closely associated with the oxygen atom, two pairs associated with the oxygen atom as 'outer'
electrons and two pairs forming each of the two identical O-H covalent bonds. And it shape can be
shown as below;
Q U E S T I O N 4
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
What is the molarity (M) of a solution containing 1.4 mol of acetic acid (CH3COOH) in 250
ml of solution?
Molarity = moles/ volume in L
M= 1.4/0.25
M=5.6 moles/litre
Q U E S T I O N 5
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
Calculate the Molarity (M) of a HCl solution which contains 0.522g of HCl in 0.592L of
Solution.

Moles=mass/molar mass
Moles=0.522/98
Moles=0.005326
Molarity = moles/ volume in L
M=0.005326/0.592
M=0.0089975 moles/litre
Q U E S T I O N 6
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
What is the molarity of a solution made by dissolving 2.00g of potassium chloride (KCl) in
enough water to make 150 ml of solution?
Moles=2/74.5
Moles=0.026845
Molarity = moles/litre
Molarity =0.026845/0.15
Molarity=0.1789
Q U E S T I O N 7
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
How many grams of potassium hydroxide (KOH) are required to prepare 600 ml of 0.450 M
KOH solution
moles= molarity * volume (L)
moles= 0.45*0.6
moles =0.27
mass =molar mass * moles
mass= 0.27*56
mass=15.12 g
Q U E S T I O N 8
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
Calculate the number of moles of nitric acid in 325ml of 16 M HNO3 solution
Moles= MV
Moles=16* 0.325
Moles=5.2 moles

Q U E S T I O N 9
1. Full marks will be given if you get the correct answer, however if not, marks
will be given based on the information you provide on the method you
employed to achieve the final answer.
How many mls of 2.00 M HCl will react with 28.0 g of NaOH
Moles= mass/molar mass
Moles=28/40
Moles=0.7
Volume =moles/molarity
Volume =0.7/2
Volume =0.35 L
Volume =350 ml
Q U E S T I O N 1 0
1. Briefly describe using a suitable example, how in the laboratory, you could purify an organic compound
(which is soluble in hot water, but not in cold water), from a mixture of 2 contaminants, one of which is not
soluble in water, and the other of which is soluble in both hot and cold water.
Taking example as ketones which is only soluble in hot water and ethanol which soluble in both
hat and cold water. Take the mixer solution and then subject it to a cold water, decant alcohol
which will be on the upper surface of the solution since it is lighter than the ketones. The interface
of both two liquids are poured out. Then the remnant (ketones) is collected and put in a different
container as alcohol is also put in a different container.