Ch 8 Section 1

Question 1

a chemical reaction is the process b which one or more substances are

Answer 1

changed into one or more different substances.

Question 2

in any chemical reaction, the original substances are known as the —– and the resulting substances are known as the

Answer 2

reactants, products

Question 3

according to the law of conservation of mass, the total mass of reactants must equal the

Answer 3

total mass of products for any given chemical reaction

Question 4

chemical reactions are described by

Answer 4

chemical equations

Question 5

a chemical equation represents, with symbols and formulas, the identities and relative molecular or molar amounts of the

Answer 5

reactants and products in a chemical reaction

Question 6

absolute proof of a substances’ change in identity can be provided only by

Answer 6

chemical analysis of the products

Question 7

certain easily observed changes usually indicate that a

Answer 7

chemical reaction has occurred

Question 8

(Observed changes) evolution of energy as

Answer 8

heat and light

Question 9

(a change in matter that observed changes- evolution of energy as heat and light) a change in matter that releases energy as both

Answer 9

heat and light is strong evidence that a chemical reaction has taken place

Question 10

(observed changes- evolution of energy as heat and light) heat or light by itself is not necessarily a sign of chemical change because

Answer 10

many physical changes also involve either heat or light

Question 11

(observed changes- production of a gas) the evolution of gas bubbles when two substancs are mixed is often

Answer 11

evidence of a chemical reaction

Question 12

(observed changes- formation of a precipitate) many chemical reactions take place between

Answer 12

substances that are dissolved in liquids

Question 13

(observed changes- formation of a precipitate) if a solid appears after two solutions are mixed, a

Answer 13

reaction has likely occurred

Question 14

(observed changes- formation of a precipitate) a solid that is produced as a result of a chemical reaction in solution and that

Answer 14

separates from the solution is known as a precipitate

Question 15

(observed changes- color change) a change in color is often an

Answer 15

indication of a chemical reaction

Question 16

a properly written chemical equation can summarize any

Answer 16

chemical change

Question 17

(requirements for writing correct chemical equations) the equation must represent known

Answer 17

facts

Question 18

(requirements for writing correct chemical equations) all reactants and products must be identified, either through chemical analysis in the lab or from

Answer 18

sources that give the results of experiments

Question 19

(requirements for writing correct chemical equations) te equation must contain the correct

Answer 19

formulas for the reactants and products

Question 20

(requirements for writing correct chemical equations) knowledge of the common oxidation stats of the elements and of methods of writing formulas will enable you to supply

Answer 20

formulas for reactants and products if they are not available

Question 21

(requirements for writing correct chemical equations) diatomic molecules represented in an equation by molecular formula, but other elements are represented simply by their atomic symbols, without subscripts, because the elements do not form

Answer 21

definite molecular structures (exceptions–> S8 and P4)

Question 22

(requirements for writing correct chemical equations) he law of conservation of mass must be

Answer 22

satisfied

Question 23

(requirements for writing correct chemical equations) the same number of atoms of each element must appear of

Answer 23

each side of a correct chemical equation

Question 24

(requirements for writing correct chemical equations) to balance numbers of atos add

Answer 24

coefficients where necessary

Question 25

(requirements for writing correct chemical equations) a coefficient is a small whole number that appears in front of a

Answer 25

formula in a chemical equation

Question 26

(requirements for writing correct chemical equations) placing a coefficient in front of a formula specifies the relative number of

Answer 26

moles of the substance (if no coefficient, assumed to be 1)

Question 27

the first step in writing a chemical equation is to identify the facts to be

Answer 27

represented

Question 28

a word equation is an equation in which the reactants and products in a chemical reaction are

Answer 28

represented by words

Question 29

a word equation (qualitative) does not give the whole story because it does not give the quantities of the

Answer 29

reactants used or products formed

Question 30

the next step in writing a correct chemical equation is to replace the names of the reactants and products with

Answer 30

appropriate symbols and formulas

Question 31

a formula equation represents the reactants and products of a chemical reaction by their

Answer 31

symbols and formulas

Question 32

the g in parentheses after each formula indicates that the corresponding substance is in the

Answer 32

gaseous state

Question 33

a formula equation is a

Answer 33

qualitative statement

Question 34

a formula equation represents the facts and shows the

Answer 34

correct symbols and formulas for the reactants and products

Question 35

to complete the process of writing a correct equation, the law of conservation must be

Answer 35

taken into account

Question 36

the relative amounts of reactants and products represented in the equation must be adjusted so that the number sand types of atoms are the

Answer 36

same on both sides of the equation

Question 37

process is called balancing an equation and is carried out by

Answer 37

inserting coefficients

Question 38

sometimes a gaseous product is indicated by an

Answer 38

arrow pointing upward

Question 39

a downward arrow is often used to show the formulation of a

Answer 39

precipitate during a reaction in solution

Question 40

the conditions under which a reaction takes place are often indicated by placing

Answer 40

information above or below the reaction arrow

Question 41

--> "Yields" indicates

Answer 41

result of reaction

Question 42

---->

Answer 42

reversible reaction

Question 43

(s) a reactant or product in the

Answer 43

solid state; also indicates precipitates

Question 44

↓ alternative to (s), but used only to indicate

Answer 44

a precipitate

Question 45

(l) a reactant or

Answer 45

product in the liquid state

Question 46

(aq) a reactant or product in an

Answer 46

aqueous solution (dissolved in water)

Question 47

↑ alternative to (g), but used only to indicate a

Answer 47

gaseous product

Question 48

∆ heat reactants are | → →

Answer 48

heated

Question 49

2 atm | → pressure at which reaction is

Answer 49

carried out

Question 50

pressure | → pressure at which reaction is carried out exceeds normal

Answer 50

atmospheric pressure

Question 51

0° C | → temperature at which reaction is

Answer 51

carried out

Question 52

MnO2 | → formula of catalyst used to alter the

Answer 52

rate of the reaction

Question 53

for some reactions it is important to specify the pressure at whichthe reaction occurs or to specify that the pressure must be

Answer 53

above normal

Question 54

many reactions are speeded up and can take place at lower temperatures in the presence of a

Answer 54

catalyst

Question 55

a catalyst is a substance that changes the rate of a chemical reaction but can be

Answer 55

recovered unchanged

Question 56

in many reactions, as soon s the products begin to form, they immediately begin to react with each other and

Answer 56

re-form the reactants

Question 57

the reverse reaction may occur to a greater or lesser degree than the original reaction, depending on the

Answer 57

specific reaction and the conditions

Question 58

a reversible reaction is a chemical reaction which the products

Answer 58

re-form the original reactants

Question 59

he chemical equation as a whole is similar to an algebraic equation in that it

Answer 59

expresses an equality

Question 60

the coefficients of a chemical reaction indicate relative, not absolute, amounts of

Answer 60

reactants and products

Question 61

a chemical equation usually shows the smallest numbers of atoms, molecules, or ions, that will satisfy the

Answer 61

law of conservation of mass in a given chemical reaction

Question 62

to obtain larger relative amounts we simply multiply each

Answer 62

coefficient by the same number

Question 63

the relative masses of the reactants and products of a chemical reaction can be determined from the

Answer 63

reaction's coefficients

Question 64

the reverse reaction for a chemical equation has the same relative amounts of

Answer 64

substances as the forward reaction

Question 65

because a chemical equation is like an algebraic equation, the equality can be read in

Answer 65

either direction

Question 66

there is important information that is not provided by a

Answer 66

chemical equation

Question 67

a chemical equation gives no indication of whether a reaction will

Answer 67

actually occur

Question 68

a chemical equation can be written for a reaction that may

Answer 68

not even take place

Question 69

experimentation forms the basis for confirming that a particular

Answer 69

chemical reaction will occur

Question 70

chemical equations give no info about the speed at which reactions occur or about

Answer 70

how the bonding between atoms or ions changes during the reaction

Question 71

(balancing chemical equations) identify the names of the reactants and the

Answer 71

products and write a word equation

Question 72

(balancing chemical equations) write a formula equation by substituting correct formulas for the

Answer 72

names of the reactants and the products

Question 73

(balancing chemical equations) balance the formula equation according to the

Answer 73

law of conservation of mass

Question 74

(balancing chemical equations) count atoms to be sure that the

Answer 74

equation is balanced

Question 75

occasionnaly when counting the atoms, the coefficients do not represent the smallest possible

Answer 75

whole-number ratio of reactants and products

Question 76

when this happens, the coefficients should be divided by their greatest common fact in order to obtain the

Answer 76

smallest possible whole number coefficients