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chem 400 > exam 3 > Flashcards

exam 3 Flashcards

1
Q

What is energy

A

The capacity to do work

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2
Q

What is work

A

the result of a force acting through a distance

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3
Q

what is heat

A

flow of energy caused by temperature difference

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4
Q

What is internal energy

A

sum of kinetic and potential energies

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5
Q

How does Energy Flow work?

A

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

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6
Q

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

A

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

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7
Q

What is heat capacity

A

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

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8
Q

What is the specific heat capacity

A

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

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9
Q

What is the equation for heat

A

q=mass x Cs x ∆T

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10
Q

What does qsys=-qsurr mean

A

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

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11
Q

What is an exothermic reaction?

A

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

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12
Q

What is an endothermic reaction?

A

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

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13
Q

is this endothermic or exothermic
sweat evaporating from skin

A

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)

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14
Q

is this endothermic or exothermic
water freezing in a freezer

A

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

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15
Q

What is the Principal Quantum Number (n)

A

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

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16
Q

What is the angular quantum number (l)

A

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

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17
Q

What are the letter values of l

A

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

18
Q

What is frequencies relationship to speed of light? wavelengths?

A

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

19
Q

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

A

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

20
Q

What is enthalpy?

A

the heat involved in a chemical reaction at constant pressure

21
Q

What are the four types of energy?

A

Kinetic, Potential. thermal, chemical energy

22
Q

What are the unit conversions of energy?

A

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

23
Q

What is a state function?

A

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).

24
Q

What are the equations to describe heat

A

q=mCs∆T (for individual substances)

q=Ccal∆T (for calorimeters)

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

25
Q

How is work related to pressure and volume?

A

w= -P∆V

26
Q

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

A

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

27
Q

What is ∆Hrxn?

A

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

∆Hrxn=qrxn/mol

28
Q

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

A

-6.0x10^5 J/mol

29
Q

what is the Pauli exclusion principle?

A

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

30
Q

What elements have a gaseous standard state?

A

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

31
Q

What elements have a standard state in liquid?

A

H20, Br2, Hg

32
Q

What elements are solids at standard state?

A

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

33
Q

What is the relationship of qcal to qrxn?

A

qcal=-qrxn

34
Q

What are the units of energy?

A

J/g °C, J/mol °C, cal/g °C

35
Q

Whats the units for enthalpy?

A

kJ/mol

36
Q

What is the formula for ∆H rxn

A

qrxn/mols

37
Q

What is Coulomb’s Law?

A

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

38
Q

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

A

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)

39
Q

What is the trend of Zeff across a row

A

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

40
Q

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

A

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

41
Q

What is diffraction?

A

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

chem 400 (9 decks)

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