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AP chem > Test #2 > Flashcards

Test #2 Flashcards

1
Q

What is thermochemistry?

A

The study of energy associated with chemical reactions

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2
Q

What is energy?

A

The ability to transfer heat (q) or do work (w)

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3
Q

What is heat (q)?

A

The ability to change temperature. Flows spontaneously from high to low.

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4
Q

What is work (w)?

A

Energy used to cause an object to move against a force.

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5
Q

What is kinetic energy?

A

The motion/speed of particles - relates to temperature. (KE=1/2mv2)

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6
Q

What is potential energy and how is electrostatic potential energy calculated?

A

The attraction or repulsion of charges.
(Eel=KQ1Q2/d)
Q1/Q2 = mass of charges
d = distance between charges

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7
Q

What are some conversion factors?

A

1 kJ = 1000 J
1 cal = 4.184 J
1 kcal = 1,000 cal = 1 Cal (dietary calorie)

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8
Q

What is the difference between the system and the surroundings?

A

System - the thing being studied (the reaction)
Surroundings - everything else outside the reaction

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9
Q

What is an open system?

A

A system that transfers heat and matter

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10
Q

What is a closed system?

A

A system that transfers heat but not matter

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11
Q

What is an isolated system?

A

A system that does not transfer heat or matter

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12
Q

What is the first law of thermodynamics?

A

Energy is conserved

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13
Q

What is internal energy?

A

The sum of all the kinetic/potential changes in a system.
Change in energy = heat + work

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14
Q

What is an exothermic reaction?

A

Heat was lost by the system (-q)

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15
Q

What is an endothermic reaction?

A

Heat was absorbed by the system (+q)

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16
Q

What does it mean to have -w?

A

Work was done BY the system ON the surroundings

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17
Q

What does it mean to have +w?

A

Work was done ON the system BY the surroundings

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18
Q

What is enthalpy?

A

The heat of a reaction at constant pressure when the only work done is pressure-volume work.

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19
Q

What is a thermochemical equation?

A

A chemical equation that also includes the change in heat information at the end

20
Q

What is calorimetry?

A

A lab method for measuring the heat exchange involved in physical or chemical processes

21
Q

What is heat capacity (c)?

A

The amount of heat needed by a certain substance to change its temperature by 1 degree celsius.

22
Q

What is specific heat (cs)?

A

The amount of heat needed to change 1g of a substance by 1 degree celsius.

23
Q

What is molar heat capacity (cm)?

A

The amount of heat needed to change 1 mol of a substance by 1 degree celsius

24
Q

What happens if a substance has a large heat capacity?

A

It is hard to change its temperature. Ex. insulators (water, foam, etc.)

25
Q

What happens if a substance has a small heat capacity?

A

It is easy to change its temperature. Ex. conductors (metals)

26
Q

What is the calorimetry equation?

A

Allows us to calculate heat transfer.

q=mc(change in)T

q = heat
m = mass of substance changing temp.
c = specific heat
(change in) T = change in temp.

27
Q

What are the steps of Hess’ Law?

A
  1. Get things on the right side of the reactions
  2. Look to make sure coefficients are correct
  3. Start canceling out
  4. Combine/cancel
28
Q

What is electromagnetic radiation?

A

Energy transmission in the form of a wave traveling at the speed of light.
Red/Orange/Yellow - Low energy - 750 nm
Green/Blue/Violet - High energy - 400 nm

29
Q

What is the conversion factor to convert nanometers to meters?

A

1 meter = 1 x10^9 nanometers

30
Q

What is Avogadro’s number and what does it tell us?

A

6.02 x 10^23
It tells us how many particles (either atoms or molecules) are in 1 mol of a substance.
1 mol = 6.02 x 10^23

31
Q

What is the atomic emission spectra?

A

Bohr observed that when elements were heated or electrified, they emitted unique colors of light

32
Q

Why are the spectra unique?

A

Every atom has a specific number of protons and thus the energy levels are at different distances from the nucleus. Every atom has a unique radius.

33
Q

What does the Bohr model demonstrate?

A
  • Describes the atom as a small, positively charged nucleus surrounded by electrons that travel in specific circular orbits
  • When an electron moves from a lower to higher energy level, it absorbs energy
  • When an electron moves from a higher to lower energy level, it emits a photon of light
34
Q

What are some limitations of the Bohr model?

A
  • It only works mathematically for hydrogen
  • Doesn’t explain bonding
  • Electrons don’t actually move in set circular orbits
  • The fact that electrons exist in different energy levels, transition between them, and emit light still apply
35
Q

What is Heisenburg’s uncertainty principle?

A

It is impossible to know both the momentum and location of an electron at the same time.

36
Q

What did DeBroghe discover?

A

Electrons have wave-like properties

37
Q

What is the Aufbau Principle?

A

Electrons fill from the lowest energy orbital to the higher energy orbitals

38
Q

What is the Pauli exclusion principle?

A

Electrons must have opposite spins in order to reduce repulsions and occupy the same orbital

39
Q

What is Hund’s rule?

A

Electrons spread out within a sublevel before pairing up

40
Q

What is periodic law?

A

When organized by atomic #, there is a periodic repetition of properties after a series of 1-8 valence electrons

41
Q

What is effective nuclear charge (Zeff)?

A

The charge or “pull” felt by the outermost valence electron from the protons in the nucleus.
Zeff = # protons (atomic #) - shielding e- (nonvalence e-)

42
Q

What is atomic radius?

A

The distance from the nucleus to the outermost valence electrons

43
Q

What is ionic radius?

A

The distance from the nucleus to the outermost valence electrons after an atom has gained or lost electrons

44
Q

What are the radius trends?

A
  • Down a group, atomic radius increases.
  • Across a period, atomic radius decreases
  • Across a period, Zeff increases and principle energy level stays the same and gets pulled in closer by the increasing nuclear charge
45
Q

What happens to the ionic radius when at atoms loses an electron?

A

It gets smaller

46
Q

What happens to the ionic radius when at atoms gains an electron?

A

It gets bigger

47
Q
A

AP chem (3 decks)

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