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a. Draw the final Lewis Diagram (final structure only) using lines for bonds.

b. Write the kind of molecular shape. In case of more than one central atom, write the

shape at each central atom (#15, 18, 19, 26, 27, 30).

c. Write "crystal lattice" for ionic compounds under "Molecular Shape".

d. Polar or nonpolar (omit polar /non polar for polyatomic ions and ionic compounds).

e. For polar molecules, clearly label the overall molecular dipole (with a dipole

arrow) on the Lewis Diagram.

Formula

1. H2

2. CO

Lab Report #15: Molecular Shapes [30 points]

3. CH4

Lewis Diagram

Molecular Shape

Polar or

Non polar?/nChemistry 2A

Yuba College

Lab #16: Balancing Chemical Equations

Chemical equations must be (mass-)balanced in order to obey the Law of

Conservation of Mass, which states that matter is neither created nor destroyed. (In

addition, each of the various types of chemical calculations which we will be studying

throughout the remainder of this course requires a balanced equation.) A balanced

equation has equal numbers of each element on each side of the equation. Therefore, a

real chemical reaction must finish with as many atoms of each element as when it started.

Consider the following example,

H2 + O2 → H₂O

This is an unbalanced equation, also called a 'skeleton' equation. Notice that there are two

atoms of hydrogen on each side, BUT there are two atoms of oxygen on the left side and

only one on the right side. Remember this: A balanced equation MUST have EQUAL

numbers of EACH type of atom on BOTH sides of the arrow.

An equation is balanced by changing coefficients in a trial-and-error fashion. A

coefficient is a multiplier of a chemical formula. For example, the formula (NH4)2S

represents two atoms of nitrogen with eight atoms of hydrogen and one atom of sulfur.

When a coefficient of two is placed in front of the formula, i.e.,

2 (NH4)2S

we now have two copies of (NH4)2S so we have twice as much as before, i.e., four atoms of

nitrogen, sixteen atoms of hydrogen and two atoms of sulfur.

Chemical equations are NEVER balanced by changing the subscripts of the formulas

involved. For example, the skeleton equation

Fig: 1

Fig: 2