last test study guide

Question 1

equilibrium

Answer 1

usually, less than 100% of the reactants are converted to products

Question 2

forward reaction

Answer 2

reactants to products

Question 3

reverse reaction

Answer 3

products to reactants

Question 4

equilibrium is reached when

Answer 4

rate of forward rxn = rate of reverse rxn

Question 5

le chatelier’s principle

Answer 5

to compensate for a change in concentration

if the reverse rxn happens quickly, chemist may try to shut it down to maximize yield

Question 6

less reactants formed means

Answer 6

forward rxn slows (less products)

Question 7

more reactants formed means

Answer 7

forward rxn speeds up (more products)

Question 8

forward rxn happens faster when

Answer 8

less products are present

Question 9

reverse rxn happens faster when

Answer 9

more products present/less reactant present

Question 10

thermodynamics

Answer 10

the study of thermal energy, heat, and work and how they are related

Question 11

1st law of thermodynamics

Answer 11

energy cannot be created or destroyed (only changes form)

Question 12

2nd law of thermodynamics

Answer 12

heat naturally flows from a warmer object to a cooler object

Question 13

exothermic rxn

Answer 13

gives off heat

moves energy released in forming new bonds

Question 14

endothermic rxn

Answer 14

absorbs heat

less energy is produced in forming bonds than what is required

Question 15

energy diagrams

Answer 15

represent the overall energy of chemicals in the rxn

Question 16

exothermic energy diagram

Answer 16

start with a high activation energy and decrease at the end

Question 17

endothermic energy diagram

Answer 17

start with a low activation energy and increases to the end

Question 18

activation energy

Answer 18

the amount of energy required to break bonds and kickstart a reaction (E^a)

Question 19

enthalpy (H)

Answer 19

the measurement of total energy in the system (heat)

find it through Hf - Hi

Question 20

Hf

Answer 20

means final enthalpy

Question 21

Hi

Answer 21

means initial enthalpy

Question 22

an energy graph going up to down

Answer 22

negative enthalpy

Question 23

an energy graph going down to up

Answer 23

positive enthalpy

Question 24

endothermic

Answer 24

reactions have a positive H because the products have more energy than reactants

moves up

Question 25

exothermic

Answer 25

reactions have negative H because the products have less energy than reactants

moves down

Question 26

density

Answer 26

the amount of mass in each unit of volume

Question 27

intensive property

Answer 27

that doesn’t change with size of sample (density, tensile strength, bounce)

Question 28

extensive property

Answer 28

does change with size of sample (mass, volume, weight)

Question 29

physical property

Answer 29

one that can be determined without changing the substance identity (length, compressive, conductivity)

Question 30

density is a

Answer 30

derived unit (mass divided by volume) used as a conversion factor

Question 31

the seven derived base units

Answer 31

amount, length, mass, time, electric current, temperature, light intensity

Question 32

heat capacity

Answer 32

how quickly heat affects temperature

Question 33

specific heat

Answer 33

the amount of heat needed to raise the temperature of 1kg of a substance by 1 C

4184 J / kg * C (remember, it’s for water)

Question 34

water can absorb lots of heat without a large change in temperature because

Answer 34

of hydrogen bonds hindering the movement

Question 35

Q = m T C

Answer 35

m = grams
C = specific heat
T = change in temp

used to calculate the amount of heat associated with a change in temperature

Question 36

-Q means

Answer 36

heat is released to LOWER temperature (-T)

freezing or condensation (exothermic)

Hvap

Question 37

+ Q means

Answer 37

heat is required to RAISE temperature (+T)

melting or vaporization (endothermic)
Hfus

Question 38

Q = nHfus and Q = nHvap used for

Answer 38

when changes of state involve heat but DONT change temperature

Question 39

Q = nHfus and Q = nHvap

Answer 39

n = moles
Hfus = molar enthalpy of fusion (J/mol)
Hvap = molar enthalpy of vaporization (J/mol)

Question 40

calorimeter

Answer 40

a device with an insulated chamber that is used to measure specific heat

Question 41

radioactivity

Answer 41

protons held together by neurons

neurons contribute to the STRONG nuclear force

Question 42

small atoms need

Answer 42

1:1 ratio (rows 1-3)

Question 43

larger atoms need

Answer 43

3:2 ratio (rows 6-7)

Question 44

too many or too few neurons can result into

Answer 44

unstable nucleus

Question 45

stable isotopes always need

Answer 45

the neurons and protons ratio to be between 1.0 and 1.5

Question 46

alpha decay

Answer 46

a very large nucleus emits alpha particles, making itself smaller, releases gamma radiation (2p+, 2n)

has a helium or alpha sign added to products
(top n - 4, bottom n - 2)

Question 47

beta decay

Answer 47

a neuron emits an electron and becomes a proton, releases gamma radiation (top n = n, bottom n + 1)

has a negative electron added to products

Question 48

positron emission

Answer 48

a proton emits a positron and becomes a neutron (top n = n, bottom n - 1)

has a positive electron added to products

Question 49

electron capture

Answer 49

an electron is captured by the nucleus to become a neutron when it combines with a proton (top n = n, bottom n - 1)

has a negative electron added to reactants

an x-ray photon could be added to products

Question 50

59
28 Ni

Answer 50

59 = mass number
28 = atomic number

Question 51

half life

Answer 51

(T) the time required for one half of a radioactive isotope’s nuclei to decay into its daughter isotopes

grams * (1/2) ^ (t/T)

t = elapsed time
T = half life

Question 52

decay process occurs at a

Answer 52

predictable rate and is NOT influenced by factors such as temperature, pressure, and concentration