Exam 1

Question 1

where is most of the mass of the atom concentrated in?

Answer 1

the dense, tiny nucleus

Question 2

what comprises the nucleus?

Answer 2

neutrons and protons, collectivily called nucleons

Question 3

nuclide:

Answer 3

a nucleus with a particular composition. Each isotope of an element has a different nuclide.

Question 4

alpha decay

Answer 4

• a helium nucleus
• 42 He^2+
• can’t penetrate paper
• lots of proton and neutrons

Question 5

beta decay

Answer 5

• a fast electron
• 0 -1 e
• can penetrate paper, stops at aluminum
• n>p

Question 6

gamma decay

Answer 6

• a photon, no charge, no mass

- can penetrate paper, aluminium, stops at lead

Question 7

neutron

Answer 7

• 1 0 n

- can penetrate paper, aluminum, lead. stops at concrete

Question 8

chemical reactions

Answer 8

• atoms retain their identity
• reactions involve only electrons and usually only outermost electrons
• reaction rates can be increased by raising the temperature
• the energy absorbed or given off in reactions is comparatively small
• mass is conserved, the mass products equals the mass of starting materials

Question 9

nuclear reactions

Answer 9

• atoms usually change their identity – from one element to another
• reactions involve mainly protons and neutrons. It does not matter what the valence electons do
• reaction rates are unaffected by changes in temperature
• reactions sometimes involve enormous changes in energy
• huge changes in energy are accompanied by measurable changes in mass (E=mc^2)

Question 10

geiger counters

Answer 10

measures activity: disintegrations over time

Question 11

n/p too large (too many neutrons)

Answer 11

• increase number of protons

- beta decay: neutron decays to proton plus a beta particle

Question 12

p/n too large (too many protons)

Answer 12

• increase neutrons, or reduce protons

- position decay or electron capture

Question 13

above the band of stability

Answer 13

• alpha decay

Question 14

B+ emission/e- capture

Answer 14

p>n

Question 15

in a _________ reaction, the energy changes in breaking or forming bonds is relatively small, so mass changes are negligible

Answer 15

chemical

Question 16

in a _______ reaction, the energy changes are enormous and the changes are easily measurable

Answer 16

nuclear

Question 17

nuclear binding energy:

Answer 17

the energy required to convert a nucleus to protons and neutrons
- usually in energy per atom/nuclide in eV or MeV

Question 18

mass defect

Answer 18

• mass of nucleus is not equal to the sum of the masses of individual nucleons in the nucleus
• the missing amu between the sum of n+p and the experimental mass
• equated with the energy required to hold nuclear particles together

Question 19

the greater the bidning energy per nucleon, the

Answer 19

the more stable the nucleus

Question 20

binding energy per nucleon maximizes around what?

Answer 20

56 Fe

Question 21

fission:

Answer 21

the release of energy by splitting heavy nuclei such as Uranium-235 and Plutonium-239. into smaller nuclei using neutron bombardment. The energy from the reaction drives a steam cycle to produce electricity.

Question 22

fusion:

Answer 22

the release of energy by combining two light nuclei such as deuterium and tritium. more dangerous not easy to control

Question 23

mass required to achieve the fissio process becoming seld-sustainging by a chain reaction is called

Answer 23

critical mass

Question 24

in what ways is nuclear fission different from radioactive decay?

Answer 24

nuclear fission has neutron bombardment making it split heavy nuclei. Radioactive decay is spontaneous disintegration into radiation

Question 25

the ideal gas law

Answer 25

``` PV= nRT p = pressure (atm) V = volume (L) n = number of moles (no units) T = temperature (K) R = gas constant -> 0.08205 (atm L)/(mol K) ```

Question 26

acid:

Answer 26

a substance that produces H+ ions when dissolved in H2O

Question 27

base:

Answer 27

a substance that produces OH- ions when dissolved in H2O

Question 28

acid-base reaction is also called a

Answer 28

neutralization reaction

Question 29

kinetic energy:

Answer 29

the energy of motion - mechanical energy - thermal energy - electrical energy

Question 30

potential energy:

Answer 30

stored energy - gravitational energy - electrostatic energy (energy of charged particles) - chemical potential energy (energy of attraction or repulsion among electrons and nuclei)

Question 31

the chemical bonds in sugar is what type of energy?

Answer 31

potential

Question 32

law of conservation of energy:

Answer 32

energy is neither created nor destroyed, it is only ocnverted between forms

Question 33

internal energy:

Answer 33

- sum of PE and KE of all particles that make up a system E= KE+PE - a change in E of a system is always accompanied by an opposite change in E of surroundings

Question 34

a reacting chemical system can change its internal energy in either of two ways:

Answer 34

- losing E to surroundings - gain E from surroundings the transfer from system to surrounding, this transfer can appear as heat or work

Question 35

work

Answer 35

w= -p delta v

Question 36

energy released to surroundings

Answer 36

delta E= -

Question 37

energy absorbed from surroundings

Answer 37

delta E= +

Question 38

2 mol of gas -> 4 mol of gas

Answer 38

work of expansion, work done by the system on surrounding. delta v > 0, p=constant, w<0

Question 39

2 mol of gas -> no gas

Answer 39

volume contraction, delta v < 0, p=constant, w>0

Question 40

3 mol of gas -> 3 mol of gas

Answer 40

delta v=0, p=constant, w=0, no work is done

Question 41

the transfer of E can appear as

Answer 41

heat or work

Question 42

heat:

Answer 42

energy transfer as result of difference in temperatures

Question 43

work:

Answer 43

energy transfer when object moved by force

Question 44

chemical reactions usually do two kinds of work:

Answer 44

``` electrical work (drive electric current through wire) work of expansion (volume of system changes) ```

Question 45

if q is positive

Answer 45

the system gains heat

Question 46

if q is negative

Answer 46

the system releases heat

Question 47

if w is positive

Answer 47

work is done ON the system

Question 48

if w is negative

Answer 48

work is done BY the system

Question 49

law of thermodynamics

Answer 49

total energy of a system plus surroundings remains constant | delta E universe = delta E system + delta E surroundings = 0

Question 50

state functions or no state functions

Answer 50

value of a state function depends on the state of the system -- not how we arrived at the state. Internal energy is a state function

Question 51

enthalpy:

Answer 51

chemical change at constant pressure

Question 52

the most common chemical work

Answer 52

PV work

Question 53

if a system remains at constant pressure and its volume does not change much, then

Answer 53

delta H approx.= delta E

Question 54

delta H

Answer 54

the change in heat for a system at constant pressure

Question 55

heat of reaction (delta Hrxn)

Answer 55

enthalpy change for a chemical reaction (exo)

Question 56

heat of combustion (delta H comb)

Answer 56

enthalpy change for the chemical reaction when 1 mol of a substance reacts with O2

Question 57

heat of formation (deltaHf)

Answer 57

enthalpy change for the chemical reaction when 1 mol of a compound is produced from its component elements (exo)

Question 58

heat of fusion (delta H fus)

Answer 58

enthalpy change for the melting (or freezing) of 1 mol of a substance (endo)

Question 59

heat of vaporization (delta H vap)

Answer 59

enthalpy change for the vaporization (or condensation) of 1 mol of a substance (endo)

Question 60

specific heat capacity (c)

Answer 60

of a substance is the quantity of heat required to change the temperature of 1 gram of the substance by 1 K

Question 61

cold pack

Answer 61

endothermic (heat is absorbed)

Question 62

heat pack

Answer 62

exothermic (heat is released into the environment)