Ch 8 Section 1 Flashcards Preview

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Flashcards in Ch 8 Section 1 Deck (76):
1

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

changed into one or more different substances.

2

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

reactants, products

3

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

total mass of products for any given chemical reaction

4

chemical reactions are described by

chemical equations

5

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

reactants and products in a chemical reaction

6

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

chemical analysis of the products

7

certain easily observed changes usually indicate that a

chemical reaction has occurred

8

(Observed changes) evolution of energy as

heat and light

9

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

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

10

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

many physical changes also involve either heat or light

11

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

evidence of a chemical reaction

12

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

substances that are dissolved in liquids

13

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

reaction has likely occurred

14

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

separates from the solution is known as a precipitate

15

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

indication of a chemical reaction

16

a properly written chemical equation can summarize any

chemical change

17

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

facts

18

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

sources that give the results of experiments

19

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

formulas for the reactants and products

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

formulas for reactants and products if they are not available

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

definite molecular structures (exceptions--> S8 and P4)

22

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

satisfied

23

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

each side of a correct chemical equation

24

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

coefficients where necessary

25

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

formula in a chemical equation

26

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

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

27

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

represented

28

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

represented by words

29

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

reactants used or products formed

30

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

appropriate symbols and formulas

31

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

symbols and formulas

32

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

gaseous state

33

a formula equation is a

qualitative statement

34

a formula equation represents the facts and shows the

correct symbols and formulas for the reactants and products

35

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

taken into account

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

same on both sides of the equation

37

process is called balancing an equation and is carried out by

inserting coefficients

38

sometimes a gaseous product is indicated by an

arrow pointing upward

39

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

precipitate during a reaction in solution

40

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

information above or below the reaction arrow

41

--> "Yields" indicates

result of reaction

42

---->

reversible reaction

43

(s) a reactant or product in the

solid state; also indicates precipitates

44

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

a precipitate

45

(l) a reactant or

product in the liquid state

46

(aq) a reactant or product in an

aqueous solution (dissolved in water)

47

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

gaseous product

48

∆ heat reactants are
→ →

heated

49

2 atm
→ pressure at which reaction is

carried out

50

pressure
→ pressure at which reaction is carried out exceeds normal

atmospheric pressure

51

0° C
→ temperature at which reaction is

carried out

52

MnO2
→ formula of catalyst used to alter the

rate of the reaction

53

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

above normal

54

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

catalyst

55

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

recovered unchanged

56

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

re-form the reactants

57

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

specific reaction and the conditions

58

a reversible reaction is a chemical reaction which the products

re-form the original reactants

59

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

expresses an equality

60

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

reactants and products

61

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

law of conservation of mass in a given chemical reaction

62

to obtain larger relative amounts we simply multiply each

coefficient by the same number

63

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

reaction's coefficients

64

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

substances as the forward reaction

65

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

either direction

66

there is important information that is not provided by a

chemical equation

67

a chemical equation gives no indication of whether a reaction will

actually occur

68

a chemical equation can be written for a reaction that may

not even take place

69

experimentation forms the basis for confirming that a particular

chemical reaction will occur

70

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

how the bonding between atoms or ions changes during the reaction

71

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

products and write a word equation

72

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

names of the reactants and the products

73

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

law of conservation of mass

74

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

equation is balanced

75

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

whole-number ratio of reactants and products

76

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

smallest possible whole number coefficients