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Chem > Ch 8 Section 1 > Flashcards

Ch 8 Section 1 Flashcards

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1
Q

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

A

changed into one or more different substances.

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2
Q

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

A

reactants, products

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3
Q

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

A

total mass of products for any given chemical reaction

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4
Q

chemical reactions are described by

A

chemical equations

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5
Q

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

A

reactants and products in a chemical reaction

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6
Q

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

A

chemical analysis of the products

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7
Q

certain easily observed changes usually indicate that a

A

chemical reaction has occurred

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8
Q

(Observed changes) evolution of energy as

A

heat and light

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9
Q

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

A

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

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10
Q

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

A

many physical changes also involve either heat or light

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11
Q

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

A

evidence of a chemical reaction

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12
Q

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

A

substances that are dissolved in liquids

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13
Q

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

A

reaction has likely occurred

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14
Q

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

A

separates from the solution is known as a precipitate

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15
Q

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

A

indication of a chemical reaction

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16
Q

a properly written chemical equation can summarize any

A

chemical change

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17
Q

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

A

facts

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18
Q

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

A

sources that give the results of experiments

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19
Q

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

A

formulas for the reactants and products

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20
Q

(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

A

formulas for reactants and products if they are not available

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21
Q

(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

A

definite molecular structures (exceptions–> S8 and P4)

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22
Q

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

A

satisfied

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23
Q

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

A

each side of a correct chemical equation

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24
Q

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

A

coefficients where necessary

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25
Q

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

A

formula in a chemical equation

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26
Q

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

A

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

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27
Q

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

A

represented

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28
Q

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

A

represented by words

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29
Q

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

A

reactants used or products formed

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30
Q

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

A

appropriate symbols and formulas

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31
Q

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

A

symbols and formulas

32
Q

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

A

gaseous state

33
Q

a formula equation is a

A

qualitative statement

34
Q

a formula equation represents the facts and shows the

A

correct symbols and formulas for the reactants and products

35
Q

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

A

taken into account

36
Q

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

A

same on both sides of the equation

37
Q

process is called balancing an equation and is carried out by

A

inserting coefficients

38
Q

sometimes a gaseous product is indicated by an

A

arrow pointing upward

39
Q

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

A

precipitate during a reaction in solution

40
Q

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

A

information above or below the reaction arrow

41
Q

–> “Yields” indicates

A

result of reaction

42
Q

—->

A

reversible reaction

43
Q

(s) a reactant or product in the

A

solid state; also indicates precipitates

44
Q

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

A

a precipitate

45
Q

(l) a reactant or

A

product in the liquid state

46
Q

(aq) a reactant or product in an

A

aqueous solution (dissolved in water)

47
Q

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

A

gaseous product

48
Q

∆ heat reactants are

→ →

A

heated

49
Q

2 atm

→ pressure at which reaction is

A

carried out

50
Q

pressure

→ pressure at which reaction is carried out exceeds normal

A

atmospheric pressure

51
Q

0° C

→ temperature at which reaction is

A

carried out

52
Q

MnO2

→ formula of catalyst used to alter the

A

rate of the reaction

53
Q

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

A

above normal

54
Q

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

A

catalyst

55
Q

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

A

recovered unchanged

56
Q

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

A

re-form the reactants

57
Q

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

A

specific reaction and the conditions

58
Q

a reversible reaction is a chemical reaction which the products

A

re-form the original reactants

59
Q

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

A

expresses an equality

60
Q

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

A

reactants and products

61
Q

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

A

law of conservation of mass in a given chemical reaction

62
Q

to obtain larger relative amounts we simply multiply each

A

coefficient by the same number

63
Q

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

A

reaction’s coefficients

64
Q

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

A

substances as the forward reaction

65
Q

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

A

either direction

66
Q

there is important information that is not provided by a

A

chemical equation

67
Q

a chemical equation gives no indication of whether a reaction will

A

actually occur

68
Q

a chemical equation can be written for a reaction that may

A

not even take place

69
Q

experimentation forms the basis for confirming that a particular

A

chemical reaction will occur

70
Q

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

A

how the bonding between atoms or ions changes during the reaction

71
Q

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

A

products and write a word equation

72
Q

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

A

names of the reactants and the products

73
Q

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

A

law of conservation of mass

74
Q

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

A

equation is balanced

75
Q

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

A

whole-number ratio of reactants and products

76
Q

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

A

smallest possible whole number coefficients

Chem (54 decks)

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