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Flashcards in Chapter 7 Deck (50):
1

What two things play an important role in determining the extent and speed of a chemical reaction?

1) Thermodynamics, which deals with energy changes in chemical reactions
2) Kinetics, which describes the rate or speed of a chemical reaction

2

Thermodynamics

study of energy, work, and heat

3

3 Basic laws of thermodynamics?

1) energy cannot be created or destroyed, only converted from one form to another
2)the universe spontaneously tends toward increasing disorder or randomness
3)the disorder of a pure, perfect crystal at absolute zero is zero 0 (Kelvin)

4

Average kinetic energy of atoms or molecules does what with increasing temperature?

Increases

5

What happens when some collisions of molecules occur with sufficient energy?

can break bonds in molecules

6

What can happen when a reactant bond is broken?

new bonds may be formed and products result

7

System?

contains the process under study

8

Surroundings?

encompass the rest of the universe (system)

9

Heat

transfer of thermal energy to the surroundings; sometimes consider heat flow

10

Calorimetry

Experimental strategies for measuring temperature change and calculating heats of reactions

11

Exothermic reaction

Releases energy to the surroundings (surroundings become warmer)
representative with a negative sign

12

Endothermic reaction

absorbs energy from the surrounds (surrounding become colder)
representative with a positive sign

13

Enthalpy

term used to represent heat and is symbolized as H

14

If H reactants > H products, what is H?

H must be negative and the reaction is exothermic

15

If H reactants < H products, what is H?

H must be positive and the reaction is endothermic

16

Entropy

A measure of the randomness of a chemical system.

17

Symbol for entropy?

symbol S

18

Free Energy

symbol G, represents the combined contribution of the enthalpy and entropy values for a chemical reaction

19

4 situations of G

-H (neg) & S (pos), G is always pos, regardless of temp
-H (pos) & S (neg), G is always neg, regardless of temp
-H (pos) & S (neg), G depends on temp
-H (neg) & S (neg), G depends on temp

20

specific heat

number of calories (cal) of heat needed to raise the temperature of 1 gram (g) of the substance 1 degree Celsius (c).

21

Quantity of heat absorbed or released by the reaction (Q)?

mass of solution in the calorimeter (Ms), (X)
specific heat of the solution (SHs), (X)
change in temperature (Ts) of the solution

22

Fuel Value

is the amount of energy per g of food

23

Nutritional Calories (Cal)

equivalent to one kilo-calorie (1000 cal), known as the large Calorie

24

bomb caloriemeter

measurement of the fuel value (Cal) of foods

25

Effective collision

producing product molecules (requires sufficient energy and, in the case of complex molecules, the proper orientation of reaction molecules.

26

Activation energy

Ea, minimum amount of energy required to initiate a chemical reaction

27

Activated complex

reaction proceeds from reactants to products through an extremely unstable state

28

Factors that affect reaction rate

1) structure of the reacting species
2) molecular shape and orientation
3) the concentration of reactants
4) the temperature of reactants
5) the physical state of reactants
6) the presence of a catalyst

29

Catalyst

substance that increases the reaction rate

30

K

rate constant @ specific temp

31

rate laws

rate being equal to the rate constant multiplied by the reactant concentration raised to an exponent

32

equilibrium reactions

reactions that do not go to completion. no further obvious change is taking place, measurable quantities of reactants and products remain

33

reversible reaction

process that can occur in both directions

34

dynamic equilibrium

situation in which the rate of the forward process in a reversible reaction is exactly balanced by the rate of the reverse process

35

equilibrium constant

Keq = products/reactants

36

Is Keq temp dependent or not?

temp dependent

37

what temp is equilibrium constant reported at?

25 degree C

38

Molarity?

(mol/L)

39

LeChatelier's principle

if a stress is placed on a system at equilibrium, the system will respond by altering the equilibrium composition in such a way to minimize the stress

40

Add product, equilibrium shifts to the ?

Left

41

Add reactant, equilibrium shifts to the ?

Right

42

N2(g) + 3H2 (G) 2NH3 (g) + kcall is a what reaction?

exothermic

43

How does equilibrium shift when heat is added to exothermic reaction?

will shift left

44

How does equilibrium shift when heat is removed from an exothermic reaction?

will shift right

45

How does equilibrium shift when heat is added to endothermic reaction?

will shift right

46

How does equilibrium shift when heat is removed from an endothermic reaction?

will shift left

47

39 kcal + 2N2(g) + O2(g) 2N2O(g) is what type of reaction?

endothermic reaction

48

Pressure on an equilibrium reaction does what to reaction

shifts to the side that has the least amount of mole

49

pressure released on an equilibrium reaction does what to the reaction

shifts to the side that has the most amount of moles

50

Catalyst do what to an equilibrium reaction?

no change