Chemistry Tutorial

Basic Chemistry Tutorial ( Molarity)
A. The Periodic Table
All matter is made of atoms. Matter that is made up of just one type of atoms is said to
me an element. There are 109 elements named to date. The elements have been
arranged, according to some of their properties, into a periodic table of elements. You
will need to refer to this periodic table throughout this tutorial. You can find one on page
82 of your textbook or download at
On the periodic table, each element contains a chemical symbol, its name, its atomic
number, and its atomic mass. The number above the symbol is called the atomic number.
It is what defines the atom since it states the number of protons found in the atom’ s
nucleus. The number below the symbol is the atomic mass number. The mass number is
equal to the number of protons and neutrons found in the nucleus.
1. What is the chemical symbol for Lithium?
2. What is the chemical symbol for Sodium?
3. What is the atomic number for Oxygen?
4. What is the atomic number for Aluminum?
5. How many protons does Chlorine have?
6. How many protons does Carbon have?
7. What is the atomic mass of Fluorine?
8. What is the atomic mass of Calcium?
9. How many neutrons does Hydrogen have?
10. How many neutrons does Potassium have?
B. Chemical Compounds
When atoms of different clements are bound together by chemical bonds, a chemical
compound is the result. Chemical compounds result because they are often more stable
than the individual elements. For example, sodium (Na) is so unstable that it is explosive
in water while Chlorine (Cl) is poisonous to the human body. However, when sodium
and chlorine bind together, they create a compound called sodium chloride (NaCl) which
is a very stable compound – table salt. NaCl is neither explosive or poisonous.
In general, atoms from opposite sides of the periodic table will bind together to create
ionic compounds. These atoms join together because of the number of electrons they
have circling the outer orbit around the nucleus. Because the atoms in a compound may
have different numbers of these outer orbit (valence) electrons, they do not always join
together in a one-to-one ratio. Therefore, subscripts are use to denote when more than
one atom is needed to bind to another element in the compound. In CaCl2, there is one
atom of calcium for every two atoms of chlorine. For Al2O3, there are two atoms of
aluminum for every three atoms of oxygen. To further confuse us, atoms sometimes join
together before joining together with another element. The two atoms have a charge and
are called polyatomic atoms. Examples are OH-, SO4-2, PO4-3, NO3- to name a few.
Sometimes the ratio of polyatomic ions required to combine to a second atom is not a
one-to-one ratio either. When more than one copy of a polyatomic atom is needed, a
parenthesis is needed. For example, KOH has one potassium (K) and one hydroxide
(OH) polyatomic ion; however, Ca(OH)2 has one calcium (Ca) to two hydroxides (OH).
11. How many Chorine atoms are needed for the AlCl3 compound?
12. How many Magnesium atoms are needed for the Mg2O compound?
13. Explain the make up of the compound Na3P.
14. Explain the make up of Al2(SO4)3.
C. Nomenclature
Nomenclature means names. Each compound has at least a two part name. The first part
is simply the name of the first element listed. The second is the name of the second
element listed with the suffix –ide. For example, KI is potassium iodide (not iodine),
Na2O is sodium oxide (not oxygen). The ending of the compound names change when
polyatomic ions are used. The polyatomic ions have their own names, such as OH –
hydroxide, SO4 – sulfate, PO4 – phosphate, NO4- nitrate, CO3 – carbonate, to name a
few. Therefore, Na2PO4 is sodium phosphate and CaCO3 is calcium carbonate.
15. What is the name for Li2S?
16. What is the name for CuSO4?
17. What is the name for NaOH?
D. Molarity
The molarity of a solution is the number of moles of the compounds in the solution per
liter of solvent. The number of moles for a compound is calculated by adding up the
atomic masses of all of the atoms that make up the solute of the solution. For example, 1
mole of NaOH weighs 40 amu (atomic mass units). The 40 comes from the following
atomic masses found on the periodic table: Na = 23, O = 16, H =1 for a total of 40. So to
make a 1 molar solution of NaOH, you would have to weigh 40 g of NaOH into 1 liter of
water. 1 mole of CaCl2 would weigh 111 g (Ca = 40 + Cl2 = 35.5 x 2 for a total of
111). The sum of all the atoms in a compound is called its formula weight or its
molecular weight.
18. What is the formula weight of water (H20)?
19. What is the molecular weight of NaCl?
20. How much CuSO4 would you weigh out to make a 1 Molar solution? How much
water would you add?
21. What if it were 0.1 Molar solution, how much would you weigh? (hint: you are
making a 1/10 of a mole solution)