exam 3

Question 1

What is energy

Answer 1

The capacity to do work

Question 2

What is work

Answer 2

the result of a force acting through a distance

Question 3

what is heat

Answer 3

flow of energy caused by temperature difference

Question 4

What is internal energy

Answer 4

sum of kinetic and potential energies

Question 5

How does Energy Flow work?

Answer 5

If reactants have a higher energy than the products, the ≠∆E is negative and energy flows out of the system into the surroundings

If reactants have lower internal energy than the products, ≠∆E is positive and energy flows into the system from the surroundsings

Question 6

What does the first law of thermodynamics state about the change in the internal energy of the system

Answer 6

∆E= q+w, the change in energy id the sum of the heat transferred and work done

Question 7

What is heat capacity

Answer 7

The quantity of heat required to change the systems temperature by 1 C

Question 8

What is the specific heat capacity

Answer 8

the amount of heat required to raise the temperature of 1 gram of the substance by 1 degree C

this can be used to quantify the relationship between the amount of heat added to a given mass of the substance and the corresponding temperature change

Question 9

What is the equation for heat

Answer 9

q=mass x Cs x ∆T

Question 10

What does qsys=-qsurr mean

Answer 10

The heat gained by the system is proportionally lost by the surroundings

Question 11

What is an exothermic reaction?

Answer 11

When heat is given off to the surroundings, making the ∆E/∆H negative

Question 12

What is an endothermic reaction?

Answer 12

It absorbs heat from the surroundings, making the ∆E/∆H positive

Question 13

is this endothermic or exothermic
sweat evaporating from skin

Answer 13

Sweat evaporating from the skin cools the skin, therefore it is endothermic with positive ∆H. The skin musr supply heat for evaporation to persist (the skin is the surroundings, and the sweat evaporating is the system)

Question 14

is this endothermic or exothermic
water freezing in a freezer

Answer 14

Water freezing in a freezer releases heat and is exothermic, with a negative ∆H. The refrigeration system in the freezer must remove heat

Question 15

What is the Principal Quantum Number (n)

Answer 15

It determines the overall size and energy of the oribital, its possible values are n= 1,2,3…

Question 16

What is the angular quantum number (l)

Answer 16

this number determines the shape of the interval, the possible values are (0,1,2…(n-1))

Question 17

What are the letter values of l

Answer 17

l=0 = s
l=1=p
l=2=d
l=3=f

Question 18

What is frequencies relationship to speed of light? wavelengths?

Answer 18

It is directly proportional to speed of light and inversely proportional to the wavelength

Question 19

What is interference and what are the two forms of it?

Answer 19

Constructive interference is when two waves of equal amplitude are in phase when they interact and results in a wave with twice the amplitude

Destructive interference is when two waves are out of phase and are not aligned, this results in a cancelled wave

Question 20

What is enthalpy?

Answer 20

the heat involved in a chemical reaction at constant pressure

Question 21

What are the four types of energy?

Answer 21

Kinetic, Potential. thermal, chemical energy

Question 22

What are the unit conversions of energy?

Answer 22

1 calorie = 4.184 J,
1 Calorie/kilocalorie= 1000 cal=4184 J
1 kilowatt-hour=3.60 x 10^6 J
1 W= 1 J/s

Question 23

What is a state function?

Answer 23

It is a function whose value only depends on the state of the system, not how the system arrived at that state

Based on established state of system (temperature, pressure, amount, and identity of system).

Question 24

What are the equations to describe heat

Answer 24

q=mCs∆T (for individual substances)

q=Ccal∆T (for calorimeters)

q= nx∆H (for phase changes and mixing solutions

Question 25

How is work related to pressure and volume?

Answer 25

w= -P∆V

Question 26

Whats the difference between a bomb calorimeter and a coffee-cup calorimeter?

Answer 26

A bomb calorimeter measures and contains a combustion reaction at a constant volume. A coffee cup calorimeter measures the change in enthalpy at a constant pressure

Question 27

What is ∆Hrxn?

Answer 27

The heat of the reaction which depends on the amount of material in the rxn (1kJ/mol)

∆Hrxn=qrxn/mol

Question 28

A 0.123 Mg (s) is reacted with HCl (aq) to create 100.0mL of sol’n in a coffee cup calorimeter. The Mg completely reacts and the solution was observed to rise from 25.6C to 32.8 C. Assuming the Cs is (4.184 J/gxC) and density of H20 is (1.00g/1ML0) find the ∆H rxn

Answer 28

-6.0x10^5 J/mol

Question 29

what is the Pauli exclusion principle?

Answer 29

No two electrons in an atom can have the same four quantum numbers. Therefore, each orbital can have a maximum of 2 electrons, each with opposing spins

Question 30

What elements have a gaseous standard state?

Answer 30

H2, N2, O2, F2,Cl2, CO, CO2, NO, noble gases

Question 31

What elements have a standard state in liquid?

Answer 31

H20, Br2, Hg

Question 32

What elements are solids at standard state?

Answer 32

I2, metals, metalloids, other non-metals not listed

Question 33

What is the relationship of qcal to qrxn?

Answer 33

qcal=-qrxn

Question 34

What are the units of energy?

Answer 34

J/g °C, J/mol °C, cal/g °C

Question 35

Whats the units for enthalpy?

Answer 35

kJ/mol

Question 36

What is the formula for ∆H rxn

Answer 36

qrxn/mols

Question 37

What is Coulomb’s Law?

Answer 37

Coulomb’s law states that the potential energy of two charged particles depends on their charges (q1 and q2) and their separation (r).

For like charges, the potential energy is positive and it decreases as the particles grow farther apart (due to repulsion)

For opposite charges, the potential energy is negative and becomes more negative as the particles get closer together (due to attraction)

The magnitude of the interaction between charged particles increases as the charges of the particles increase. An electron with a charge of -1 is more strongly attracted to a nucleus of 2+ rather than a nucleus with +1

Question 38

What is the concept of shielding and effective nuclear charge (Zeff)

Answer 38

Shielding is when the electrons within the orbitals shield another electron from experiencing the full charge of the nucleus

The effective nuclear charge is the net charge that arrises from the shielding (ex. 3+ from the nucleus and 2- from the electrons causes a net charge of +1)

Question 39

What is the trend of Zeff across a row

Answer 39

As we move across a row in the periodic table, the effective nuclear charge experienced by the electrons in the outermost principal energy level increases, resulting in a stronger attraction between the outermost electrons and the nucleus, and smaller atomic radii

Question 40

What happens to the atomic radii when moving down a column in the periodic table

Answer 40

the principal quantum number (n) of the electrons in the outermost principal energy level increases, resulting in larger orbitals and larger atomic radii

Question 41

What is diffraction?

Answer 41

When a wave encounters an obstacle or slit that is comparable to its wavelength, it bends around it and results in an interference pattern