Chem unit 8

Question 1

exothermic

Answer 1

chemical reaction that RELEASES heat
energy is on product side
delta H is negative

Question 2

endothermic

Answer 2

chemical reaction that ABSORBS heat
energy on reactant side
delta H is pos.

Question 3

does exothermic have a (-) or (+) q

Answer 3

(-)

Question 4

does endothermic have a (-) or (+) q?

Answer 4

(+)

Question 5

def of temperature

Answer 5

measure of the average kinestic energy of particles’ random motion

Question 6

def of heat (q)

Answer 6

is a measure of the total amount of energy TRANSFERRED from a object or high temp –> object of low temp

Question 7

unit for heat

Answer 7

joule/kilojoule/calorie

Question 8

def of heat capacity

Answer 8

heat required to raise temp of an object by 1 degree celcius

Question 9

def of specific heat

Answer 9

amount of energy needed to raise 1g of a substance 1 degree celsius

Question 10

formula to calculate heat/energy flow

Answer 10

q=mc(delta)t

Question 12

what is a system?

Answer 12

part of the world we want to study
ex. a reaction mixture in a flask

Question 13

open system

Answer 13

exchange both matter and energy with surroundings
ex. open reaction can, rocket engine

Question 14

closed system

Answer 14

can exchange only energy with the surroundings (matter remains fixed)
ex. sealed reaction flask

Question 15

isolated system

Answer 15

can exchange neither energy nor matter with its surroundings
(ex. thermos flask)

Question 16

is vaporization endo or exo thermic

Answer 16

endothermic- liquids must gain heat to boil and turn into gas!

Question 17

is melting endo or exo thermic

Answer 17

endothermic- heat added to ice which is why it melts!

Question 18

is freezing an endo or exo thermic

Answer 18

exothermic- heat is being lost which is why it turns to ice!

Question 19

what is the first law of thermodynamics?

Answer 19

energy cannot be created nor destroyed, only converted from one form to another

Question 20

True/False- substances with a high specific heat need more heat to change its temperature

Answer 20

true- high specific heat = stronger = small temp change when large amnt of heat added

Question 21

enthalpy def

Answer 21

heat content of a system at a constant pressure

Question 22

how to calculate enthalpy (deltaH)

Answer 22

delta H = Hprod-Hreac

Question 23

free elements have what heat of formation?

Answer 23

ZEROOOO

Question 24

requires energy to form a substance, will heat of formation be pos or negative?

Answer 24

positive or higher than 0 (endo)

Question 25

releases energy when substance forms, heat of formation will be...

Answer 25

negative or lower than 0 (exo)

Question 26

formula for heat of formation

Answer 26

deltaH_rxn = sum of delta H_fprod - sum of delta H_freact

Question 27

phase diagram always goes in what order?

Answer 27

solid, liquid, gas (SLIG)

Question 28

phase diagram- in a region, how many phases exist?

Answer 28

one!

Question 29

phase diagram- how many phases exist?

Answer 29

two exist at equilibrium

Question 30

phase diagram- how many phases exist at a triple point?

Answer 30

3 phases exist at equilibrium note: pure substances only have one triple point

Question 31

phase diagram- what is a critical point?

Answer 31

point where any higher temp/pressure, the substance can no longer exist as a liquid (gas/liquid phases are indistinguishable)

Question 32

standard temp and pressure

Answer 32

1 atm, 0 degrees celcius

Question 33

sublimation

Answer 33

s --> g

Question 34

vaporizatoin

Answer 34

l ---> g

Question 35

condensation

Answer 35

g ---> l

Question 37

Hess' Law

Answer 37

possible to add two or more thermochemical equations to produce a final equation (another way to find enthalpy)

Question 38

entropy

Answer 38

measure of the amount of disorder in a system

Question 39

rank in order from least to most entropy!

Answer 39

solid, liquid, gas

Question 42

how many directions can entropy go in?

Answer 42

two! ex. solid to liquid or vice versa

Question 43

what is a spontaeous reaction?

Answer 43

physical or chemical change that occurs with NO outside intervention at ordinary conditions ex. ice being placed on a table and melting

Question 44

does spontaneous mean quick?

Answer 44

NOOOO ex. uranium takes years to decay but is still spont bc it occurs without outside intervention

Question 45

if delta G is neg... spont or non-spont?

Answer 45

spont! (exothermic-releasing heat)

Question 46

delta G pos -->

Answer 46

non-spontaneous

Question 47

entropy equatoin

Answer 47

delta S = sum of products - sum of reactants

Question 48

Gibbs free energy

Answer 48

combined enthalpy/entropy function that determines spontaneity of a process or the amount of energy that is left after a reaction takes place

Question 49

gibbs equation

Answer 49

delta G = delta H - T x delta S

Question 50

to find gibbs you must...

Answer 50

1. determine enthalpy (deltaH) 2. determine entropy (deltaS) 3. subtract enthalpy from entropy

Question 51

calorimetry

Answer 51

process of measuring the heat in chem. reactions

Question 52

why do we use styrafoam cups in experiments?

Answer 52

good insulation