Test 3: Balancing & Classifying Chemical Reactions

Question 1

We express chemical changes using chemical __

Answer 1

equations

Question 2

We use our chemical
formulas to express how atoms rearrange from __ to __

Answer 2

reactants to products

Question 3

Equations are read from left to right: with the ___ on the left, an arrow which tells what
___ the reaction occurs in the middle, and ___ on the right.

Answer 3

reactant(s), direction, product(s)

Question 4

Dimer

Answer 4

a molecule consisting of two identical molecules linked together.

Question 5

Elemental oxygen exists as a

Answer 5

dimer: O2

Question 6

How many elements are diatomic species?

Answer 6

7

Question 7

Diatomic species

Answer 7

elements that exist as dimers of themselves.

Question 8

What are the 7 diatomic species?

Answer 8

elemental hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.

Question 9

Balancing equations determines how many __ molecules react to form how many
__ molecules

Answer 9

reactant; product

Question 10

Coeffecient

Answer 10

The numbers placed in front of formulas to balance equations (ie. 2Na)

Question 11

We balance an equation by

Answer 11

systematically adding molecules or atoms on each side by inserting a coefficient in front of the atomic symbol or molecular formula.

Question 12

We continue to add or change coefficients as needed until our reaction has the __ of
reactants and products possible while still being __.

Answer 12

lowest ratio; completely balanced

Question 13

When balancing equations, we add a coefficient number rather than change the formula because

Answer 13

it would change the identity of the product if we changed the formula

Question 14

Rules for balancing equations:

Answer 14

1 – Any element present in more than two locations should be balanced last.
2 – Any element which exists by itself in elemental form on one side of the equation should be
balanced last.
3 – If you can balance an equation by using fractions, do it! Then multiply by the denominator
to get whole number coefficients.
4 – If a polyatomic ion appears on both sides of the reaction, balance the whole ion instead of
doing it piecewise

Question 15

We categorize chemical reactions in order to

Answer 15

help us better understand them

Question 16

Three general classes of chemical reactions

Answer 16

Oxidation-reduction, precipitation, acid-base

Question 17

Oxidation-Reduction reactions occur when elements

Answer 17

gain or lose electrons

Question 18

All reactions involving covalent compounds are __ reactions.

Answer 18

oxidation-reduction

Question 19

Oxidation-Reduction reactions include (2)

Answer 19

neutral elements making ionic compounds (or vice versa) and atoms in covalent compounds
are rearranged

Question 20

Precipitation reactions occur when

Answer 20

soluble elements in an aqueous (aq) solution combine to form an insoluble compound or a solid (s)

Question 21

Precipitate

Answer 21

the insoluble solid formed in a chemical equation

Question 22

Acid-Base reactions occur when

Answer 22

H+ ions in solution and OH- ions in solution combine to make liquid water as a product.

Question 23

The key to identifying an acid-base reaction is to look for

Answer 23

the H2O(l) as a product, and then look for the
H+ and OH- ions in the reactants