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chemistry > unit 9 thermochemistry > Flashcards

unit 9 thermochemistry Flashcards

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1
Q

calorimeter

A

device used to measure heat absorbed or released

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2
Q

calorie

A

quantity of heat needed to raise the temperature of 1g of water by 1 degrees Celsius

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3
Q

Joule

A

SI unit of energy

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4
Q

enthalpy

A

heat content of a system at constant pressure

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5
Q

specific heat

A

quantity of heat needed to raise the temperature of 1g of a substance by 1 degrees Celsius

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6
Q

heat capacity

A

quantity of heat needed to raise the temperature of an object by 1 degrees Celsius

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7
Q

molar heat of fusion

A

amount of heat needed to melt one mole of a solid at constant temperature

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8
Q

sublimation

A

process by which a solid changes directly to a gas

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9
Q

exothermic reaction

A

releases heat energy

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10
Q

example of exothermic reactions:

A

combustion, rain, freezing

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11
Q

what side is the heat energy (delta H) on in an exothermic reaction?

A

the right side/product side

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12
Q

what is enthalpy?

A

The heat energy change (delta H) that takes place when reactants go to products.

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13
Q

what does a positive enthalpy mean?

A

heat is absorbed during the reaction, endothermic reaction

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14
Q

what does a negative enthalpy mean?

A

heat is released during the reaction, exothermic reaction

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15
Q

endothermic reaction

A

absorbs heat energy

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16
Q

examples of endothermic reactions:

A

photosynthesis, cooking, melting

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17
Q

what side is the heat energy on in an endothermic reaction?

A

the reactants side

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18
Q

Define the law of conservation of energy

A

energy is conserved and never created nor destroyed

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19
Q

What principle advocates for equilbrium?

A

Le Chatlier’s Principle

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20
Q

61.2 kJ + 2 [A] –> [B]

If we add more of A, which way does it shift and what increases in concentration?

A

If we add more of A, the energy would shift to the products side and B’s concentration would increase

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21
Q

61.2 kJ+ 2 [A] –> [B]

If we decrease the pressure, what way does it shift?

A

To [A], because the shift in Pressure is based on moles, and A needs to have more moles

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22
Q

61.2 kJ+ 2 [A] –> [B]

If we increase the temperature, what substance increases?

A

[B], because the kJ is on the reactants side and it needs to shift to products side

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23
Q

During phase changes, what happens to the temperature?

A

Stays constant

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24
Q

What happens to the energy when breaking bonds?

A

Energy supplied/absorbed

25
Q

What happens to the energy when forming bonds?

A

Energy released

26
Q

What is chemical potential energy?

A

The energy stored in the chemical bonds of a substance.

27
Q

Where is the temperature changing in a heating curve?

A

The diagonal lines: /

28
Q

What do heating curves show?

A

Shows how a substance’s temperature changes as heat is added and displaying phase changes

29
Q

what’s the symbol for enthalpy?

A

delta H

30
Q

How do you calculate the heat energy absorbed in a phase change in a heating curve?

A

q= n (moles) times enthalpy of fusion (delta H fus)

31
Q

Where are the phases changing in a heating curve?

A

The flat lines : —

32
Q

The 1st flat line is equal to ? :

A

The enthalpy of fusion

33
Q

The 2nd flat line is equal to ? :

A

The enthalpy of vaporization

34
Q

How do you calculate the heat energy absorbed in a phase change (ex: ice going to liquid water) from a heating curve?

A

Divide the enthalpy of vaporization by the enthalpy of fusion.

35
Q

Kinetic Energy and temperature’s relationship?:

A

Direct

36
Q

What happens in segments 1,3, and 5?

A

The kinetic energy is increasing

37
Q

What happens in segments 2 and 4 in relation to energy?

A

The potential energy is increasing

38
Q

How do you calculate the heat energy absorbed in segments 1,3, and 5?

A

Use q=mCdeltaT

39
Q

What’s a phase diagram show?

A

The different states of matter and when they transition according to temperature and pressure

40
Q

What is entropy?

A

A measure of the disorder of a system

41
Q

Example of entropy

A

A campfire

42
Q

How do you calculate the enthalpy change from products and reactants?

A

Sum of enthalpies of the product-sum of enthalpies of the reactants

or use q=mCdeltaT

43
Q

Definition of boiling

A

the process by which a liquid turns into a vapor when it is heated to its boiling point

44
Q

Definition of evaporation

A

Liquid->Gas NOT at boiling point at the surface of a liquid

45
Q

Definition of vaporization

A

Liquid->Gas AT boiling point

46
Q

More temp. and pressure required to break bonds=?

A

Stronger bonds

47
Q

Sublimation

A

solid->gas

48
Q

condensation

A

gas->liquid

49
Q

deposition

A

gas->solid

50
Q

when to use delta H fusion formula?

A

when there is a phase change

51
Q

when to use delta H vaporization formula?

A

Vaporize substance (liquid->gas)

52
Q

A higher temperature with the same volume=

A

Higher entropy

53
Q

What 4 factors affect reaction rate?

A

Presence of a catalyst, concentration, temperature, surface area

54
Q

What happens when you add a catalyst to a reaction?

A

Speeds up the reaction rate and it increases the activation energy

55
Q

What happens when you increase the temperature in a reaction?

A

The reaction rate increases as the number of effective collisions increases.

56
Q

Which combination of positive/negative delta S and delta H favors a spontaneous reaction?

A

Positive delta S, negative delta H

57
Q

thermochemistry

A

the study of the transfers of energy as heat that accompany chemical reactions and physicals changes

58
Q

what is an activated complex

A

a transitional structure that results from an effective collision that persists while old bonds are breaking and new bonds are forming

chemistry (5 decks)

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