Chapter 6 - Chemical Reactions: An Introduction

Question 0

Grape juice ferments…

Answer 0

In the production of wives

Question 1

Water is decomposed to…

Answer 1

Hydrogen and oxygen gas by an electric current

Question 2

Bombardier beetle concocts…

Answer 2

A toxic spray to shoot at its enemies

Question 3

Chemical reactions are the…

Answer 3

Heart and soul of chemistry

Question 4

Chemical reactions often give…

Answer 4

A visual signal

Question 5

Steel changes from a smooth, shiny material to a…

Answer 5

Reddish brown, flaky substance when it rusts

Question 6

Hair changes color when…

Answer 6

It’s bleached

Question 7

Solid nylon is formed when…

Answer 7

Two particular liquid solutions are brought into contact

Question 8

A blue flame appears when…

Answer 8

Natural gas reacts with oxygen

Question 9

Visual clues of chemical reactions are:

Answer 9

A color changes
A solid forms
Bubbles are produced
A flame occurs

Question 10

Reactions are not always…

Answer 10

Visible

Question 11

Sometimes the only signal that a reaction is occurring is a…

Answer 11

Change in temperature as heat is produced or absorbed

Question 12

Chemists have learned that a chemical change always involves a…

Answer 12

rearrangement of the ways in which the atoms are grouped

Question 13

when the methane in natural gas combines with oxygen in the air and burns…

Answer 13

carbon dioxide and water are formed

Question 14

We represent a chemical reaction by writing a…

Answer 14

chemical equation

Question 15

chemicals present before the reaction are called

Answer 15

the reactants - are shown to the left of an arrow

Question 16

the chemicals formed by an reaction are called…

Answer 16

the products - shown to the right of an arrow

Question 17

arrow indicates…

Answer 17

the direction of the change and is read as “yields” or “produces”

Question 18

the products contain the…

Answer 18

same atoms as the reactants but that the atoms are associated in different ways

Question 19

chemical reaction involves…

Answer 19

changing the ways the atoms are grouped

Question 20

It is important to recognize that in a chemical reaction…

Answer 20

atoms are neither created nor destroyed

Question 21

all atoms present in the reactants must be…

Answer 21

accounted for among the products

Question 22

there must be the same number of…

Answer 22

each type of atom on the product side as on the reactant side of the arrow

Question 23

making sure that the equation for a reaction obeys this rule is called…

Answer 23

balancing the chemical equation for a reaction

Question 24

a reaction is only a...

Answer 24

rearrangement of the way the atoms are grouped

Question 25

atoms are not...

Answer 25

created or destroyed

Question 26

the total number of each type of atom must be...

Answer 26

the same on both sides of the arrow

Question 27

balanced equation shows...

Answer 27

the actual numbers of molecules involved in this reaction

Question 28

when we write the balanced equation for a reaction...

Answer 28

we group like molecules together

Question 29

the chemical equation for a reaction provides us with two important types of information

Answer 29

1. the identities of the reactants and products | 2. the relative numbers of each

Question 30

besides specifying the compounds involved in the reaction, we often indicate in the equation the...

Answer 30

physical states of the reactants and products by using the following symbols

Question 31

solid

Answer 31

(s)

Question 32

liquid

Answer 32

(l)

Question 33

gas

Answer 33

(g)

Question 34

dissolved in water (in aqueous solution)

Answer 34

(aq)

Question 35

an unbalanced equation is not an...

Answer 35

accurate representation of the reaction that occurs

Question 36

whenever you see an equation for a reaction...

Answer 36

you should ask yourself whether it is balanced

Question 37

the principle that lies at the heart of the balancing process is that...

Answer 37

atoms are conserved in a chemical reaction

Question 38

atoms are just grouped...

Answer 38

together differently

Question 39

the same number of each type of atom is found...

Answer 39

among the reactants and among the products

Question 40

chemists determine the identity of the...

Answer 40

reactants and products of a reaction by experimental observation

Question 41

when methane (natural gas) is burned in the presence of sufficient oxygen gas, the products are always...

Answer 41

carbon dioxide and water

Question 42

the identities (formulas) of the compounds must never be...

Answer 42

changed in balancing a chemical equation

Question 43

the subscripts in a formula cannot be...

Answer 43

changed, nor can atoms be added to or subtracted from a formula

Question 44

most chemical equations can be balanced by...

Answer 44

trial and error-that's by inspection

Question 45

keep trying until you find the numbers of reactants and products that give...

Answer 45

the same number of each type of atom on both sides of the arrow

Question 46

we cannot change the...

Answer 46

formulas of the reactants or products

Question 47

we must balance the equation by adding more...

Answer 47

molecules of reactants and/or products

Question 48

balanced equation

Answer 48

same numbers of atoms represented on both sides of the arrow

Question 49

we can multiply or divide all parts of the original balanced equation by...

Answer 49

any number to give a new balanced equation

Question 50

each chemical reaction has...

Answer 50

many possible balanced equations

Question 51

the accepted convention is that the "best" balanced equation is the...

Answer 51

one with the smallest integers (whole numbers)

Question 52

integers are called the...

Answer 52

coefficients for the balanced equation

Question 53

the first step in obtaining the balanced equation for a reaction is always...

Answer 53

to identify the reactants and products from the description given for the reaction

Question 54

when one molecule in an equation is more complicated (contains more elements) than the others...

Answer 54

it is best to start with that molecule

Question 55

we cannot change the formula of any...

Answer 55

reactant or product when we balance an equation

Question 56

we can only place coefficients in...

Answer 56

front of the formulas

Question 57

coefficients should be the smallest integers that give...

Answer 57

a balanced equation

Question 58

the process of writing and balancing the equation for a chemical reaction consists of...

Answer 58

several steps

Question 59

step 1

Answer 59

Read the description of the chemical reaction. What are the reactants, the products, and their states? Write the appropriate formulas.

Question 60

step 2

Answer 60

Write the unbalanced equation that summarizes the information from step 1

Question 61

step 3

Answer 61

Balance the equation by inspection, starting with the most complicated molecule. Proceed element by element to determine what coefficients are necessary so that the same number of each type of atom appears on both the reactant side and the product. Do not change the identities (formulas) of any of the reactants or products.

Question 62

step 4

Answer 62

Check to see that the coefficients used to give the same number of each type of atom on both sides of the arrow. (Note that an "atom" may be present in an element, a compound, or an ion.) Also check to see that the coefficients used are the smallest integers that give the balanced equation. This can be done by determining whether all coefficients can be divided by the same integer to give a set of smaller integer coefficients.