Chapter 8

Question 1

A chemical reaction occurs when there is a?

Answer 1

change in chemical composition in one or more substance

Question 2

chemical reactions takes place where?

Answer 2

microscopic level but the results of chemical reaction are observable by naked eyes

Question 3

results of chemical reaction observable by our naked eye

Answer 3

a. a precipitate is formed or dissolved
b. a change of color
c. effervescence occurs (gas formation)
d. energy in the form of heat, light, or electricity is released

Question 4

what happens in a chemical reaction?

Answer 4

change occurs in a chemical reaction:

• chemical composition
• the ways atoms are hooked up together
• old bonds are broken and new bonds are formed

Question 5

writing chemical equations

Answer 5

Reactants ---> products
arrow = indicate change
\+ = and, reacts with, combines with
--> = to produce, to give, to geenrate
(triangle) = reaction conditions

Question 6

law of conservation of mass

Answer 6

• matter cannot be created or destroyed in a chemical reaction
• atoms are not gained or lost during chemical reaction
• must be same number of each type of atom on both side
• chemical equation must be balanced

Question 7

the physical states of the reactants/products

Answer 7

gas, liquid, solid, aqueous

Question 8

coefficient

Answer 8

the molecule “ratio” in reaction

Question 9

the diatomic molecules

Answer 9

• H2 O2 N2 Cl2 Br2 I2 F2

Question 10

the coefficients in a chemical equations tells us ?

Answer 10

how many moles of each reactants are required to produce a certain number of moles of products

Question 11

law of conservation of mass:

Answer 11

the total mass of reactants used= the total mass of products produced

Question 12

exothermic reaction

Answer 12

energy is released as the reaction occurs

hill

Question 13

endothermic reaction

Answer 13

requires the input of energy as the reaction occurs

mountain

Question 14

catalysts

Answer 14

lower the activation energy for chemical reactions

- reactions proceed more rapidly with the lowered activation energy

Question 15

when the speeds of the forward and reverse reactions are the same, the amount of reactants and products stay constant. the reversible reaction is said to reach?

Answer 15

chemical equilibrium

Question 16

le chateliers principle on chemical equilibrium

Answer 16

• any change (called stress) to an equilibrium condition upsets the equilibrium of the system
• there will be a change in the rate of the forward or reverse reaction to return the system to a new state of equilibrium
• system shifts to new state of equilibrium that relieves the stress applied

Question 17

if a reactant or a product is added to the system the equilibrium is shifted in what direction?

Answer 17

in the direction that consumes the added reactant or product

Question 18

if a reactant or a product is removed from the system, the equilibrium is shifted in?

Answer 18

the direction that increases the removed reactant or product

Question 19

result of adding catalysts to the position of equilibrium

Answer 19

no change

Question 20

Oxidation

Answer 20

• always involves Loss of Electrons (Leo)

- may involve gain of oxygen and loss of hydrogen

Question 21

reduction

Answer 21

• always involves Gain of electrons GER

- may involve loss of oxygen and gain of hydrogen

Question 22

Oxidation - reduction happens?

Answer 22

simultaneously

total # of e loss = total # of electron gain

Question 23

combination reaction

Answer 23

two or more elements (or simple compounds) combine to form one product

Question 24

decomposition reaction

Answer 24

one substance splits into two or more simpler substances

Question 25

single replacement

Answer 25

one element takes the place of a different element in a reaction compound

Question 26

double replacement reaction

Answer 26

two elements in the reactants exchange places

Question 27

8

Answer 27

8