2. Atoms of the same element always have the same number of protons,
but they may have different numbers
of neutrons.
Isotopes

4. The average atomic mass of an element is the weighted average mass of the mixture of an element’s isotopes.

5. Energy from Nuclear Reactions
E=mc2
Energy produced from the Nuclear Reaction
Difference in mass between products and reactants
Very Large Constant
(Speed of Light)2
Because the constant is so large, tiny
amounts of mass produce tons of energy
Where does the energy come from ?
In chemical reactions the energy comes from the bonds,
In nuclear reactions the energy comes from the conversion of mass to energy

6. Detection of Radioactivity and the Concept of Half-life
Half-life – time required for half of the original sample of radioactive nuclides to decay

7. Half-Life Practice
Calculate how long it would take for 120g of a radioactive isotope to decay to 15.0g if its half-life were 7.0 days.

8. Decay Practice

9. Alpha Decay Pra

10. Alpha Decay

11. Beta Decay

12. Beta Decay

13. Which has the greatest penetration ability?
Alpha, Beta, Gamma

14. Le Chatelier’s Principle
25kj + N2O4 (g) NO2 (g)
(Ea) CHANGE: SHIFT PREDICTION :
Addition of N2O Right
Addition of NO2 Left
Removal of N2O Left
Removal of NO2 Right
Decrease of container volume Left
Increase of container volume Right
Increase of temperature Right
Decrease of temperature Left

15. Barometer – device that measures atmospheric pressure
Measuring Pressure
Barometer – device that measures atmospheric pressure
Invented by Evangelista Torricelli in 1643
UNITS for Pressure
1 standard atmosphere
= atm (Atmospheres)
= mm Hg (millimeters Mercury)
= torr (Names after Torricelli, Same as mm Hg)
= 101,325 Pa (Pascal)

16. Pressure and Volume: Boyle’s Law
This graph has the shape of half of a hyperbola with an equation PV = k
Volume and pressure are inversely proportional.
If one increases the other decreases.

17. Pressure and Volume: Boyle’s Law
Another way of stating Boyle’s Law is
P1V1 = P2V2
(constant temperature and amount of gas)

18. Volume and Temperature: Charles’s Law
These graphs are lines with an equation V = bT (where T is in kelvins)
Volume and temperature are directly proportional.
If one increases the other increases.
Another way of stating Charles’s Law is V1 = V2
T T2
(constant pressure and amount of gas)

19. Volume and Moles: Avogadro’s Law

20. Volume and Moles: Avogadro’s Law
Volume and moles are directly proportional.
If one increases the other increases.
V = an
constant temperature and pressure
Another way of stating Avogadro’s Law is V1 = V2
n n2
(constant temperature and pressure)

21. The Super Combined Law The left side represents the gas before
Eliminate the Variables that are not changing!!!
The left side represents the gas before
The right side represents the gas after

22. We can ignore any part of the equation that remains constant, so
If temperature is constant:
If pressure is constant:
And if volume is constant:
Boyle’s Law
Charles’s Law

23. 1. A gas occupies 12. 3 liters at a pressure of 40. 0 mmHg
1. A gas occupies 12.3 liters at a pressure of mmHg. What is the volume when the pressure is increased to 60.0 mmHg?

24. 2. Calculate the decrease in temperature when 2. 00 L at 20
2. Calculate the decrease in temperature when 2.00 L at 20.0 °C is compressed to 1.00 L.

25. PV = nRT
P= pressure
V= volume
n = number of moles of the gas  doesn’t change
R = constant ( L atm/mol K)  doesn’t change
T = temperature
Use this equation to help you visualize what happens when you change one variable…

26. PV = nRT PV = nRT PV = nRT PV = nRT  PV = nRT Pressure increases?
Temperature must increase or volume decrease (or both) to keep the equation balanced!
Temperature decreases?
Pressure and/or volume will decrease.
PV = nRT
 PV = nRT
PV = nRT or
PV = nRT
PV = nRT  or
PV = nRT or
PV = nRT

27. Dalton’s Law of Partial Pressures
The pressure of the gas is affected by the number of particles.
The pressure is independent of the nature of the particles.

28. The Kinetic Molecular Theory of Gases - describes motion of ideal gases

29. Real Gases At high pressure the volume is decreased
Molecule volumes become important
Attractions become important

30. At 27. 00 °C a gas has a volume of 6. 00 L
At °C a gas has a volume of 6.00 L. What will the volume be at °C?
Practice

31. Temperature 7a
What is temperature?
Temperature is a measure of the average kinetic energy of molecular motion in a sample.
In a hot sample, the molecules are moving much faster than in a cold sample.

32. Enthalpy
Enthalpy (H): The amount of heat that a system can potentially give to other systems.
If ∆Hrxn is positive the reaction is endothermic (it has absorbed energy) and if ∆Hrxn is negative, it is exothermic (and has given off energy).
The enthalpy change that accompanies the heating/cooling of a pure substance is determined by the equation:
∆H = mCp∆T

33. ΔH – Heat of Reaction(ENTHALPY)
Endothermic
The products have more energy than the reactants.
Heat must be put into the reaction, so ΔH is positive.

34. Exothermic The products have less energy than the reactants.
Heat must be released from the reaction, so ΔH is negative.

35. Heat added here doesn’t change the temperature of the substance, it is causing the phase change.

36. Heat Flow Problems To calculate heat, use the following formula:
Energy = mass * specific heat * temperature change
Always given to you!

37. Calculations:
Practice Problems
If grams of water is heated from 70.0° C to 100.0° C to make a cup of tea, how much heat must be added?
Q = (m)(c)(ΔT)
4.184J/gC
Joules

38. Energy as a Driving Force
Entropy, S – function which keeps track of the tendency for the components of the universe to become disordered

39. Which one favors more Randomness?
Entropy is a thermodynamic measure of the randomness (“disorder”) in the universe.
Phase changes that result in greater molecular freedom have a positive ∆S, and those that result in less molecular freedom have a negative ∆S.
Which one favors more Randomness? 
Example: For melting, ∆S = +, for freezing ∆S = -.

40. Energy as a Driving Force
Second law of thermodynamics
The entropy of the universe is always increasing.

41. Entropy Practice Which has a +∆S? Which has a -∆S?
Water Vapor Condensing or water vaporizing
Water Vaporizing – Forming a gas increases randomness
Which has a -∆S?
Ice melting or water freezing
Water Freezing – Solids do not move therefore there is a decrease in randomness of the particles

42. BrØnsted-Lowry Model of Acids and Bases 5b
substances that are hydrogen-ion donors.
HCl + H2O → Cl- + H3O+
Base
substances that are hydrogen-ion acceptors.
NH3 + H2O  NH4+ + OH-
Note:
acid/base are always added to water
hydrogen
ion
acid
base
hydroxide
ion
According to the Bronsted-Lowry Model, what is the definition of…
An Acid?
A Base?

43. The Bronsted-Lowry concept+ Cl H O
acid
base
conjugate acid
conjugate base
conjugate acid-base pairs

44. Practice problems
Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs:
HC2H3O2(aq) + H2O(l)  C2H3O2–(aq) + H3O+(aq)
acid
base
conjugate base
conjugate acid
conjugate acid-base pairs
OH –(aq) + HCO3–(aq)  CO32–(aq) + H2O(l)
base
acid
conjugate base
conjugate acid
conjugate acid-base pairs

45. More Practice (a) HF(aq) + SO32–(aq)  F–(aq) + HSO3–(aq) acid base
conjugate base
conjugate acid
conjugate acid-base pairs
(b)
CO32–(aq) + HC2H3O2(aq)  C2H3O2–(aq) + HCO3–(aq)
base
acid
conjugate base
conjugate acid
(c)
conjugate acid-base pairs
H3PO4(aq) + OCl –(aq)  H2PO4–(aq) + HOCl(aq)
acid
base
conjugate base
conjugate acid
conjugate acid-base pairs

46. The pH Scale The “p scale” is used to express small numbers.
pH = log [H+]

47. The pH Scale
pOH scale
pOH = log [OH]
pH + pOH = 14.00

48. Practice Problem Calculate pH for a solution that has
[H+] = 1.0 x 10-9 M
Step 1) [H+] = 1.0 x 10-9 M
Step 2) -log (1.0 x 10-9 )= 9.00
Step 3) pH = 9.00

49. Practice Problem #2 Calculate pH for a solution that has
[OH-] = 1.0 x 10-6 M.
1) Kw = [H+] [OH-] = 1.0 x 10-14
2) [H+] = 1.0 x / [OH-]
3) [H+] = 1.0 x / 1.0 x = x 10-8 M
4) -log 1.0 x 10-8 = 8.00
5) pH = 8.00

50. Practice Problem #3 Calculate [OH-] for a solution that has a
pH = 6.20
[OH-] = 1.6 x 10-8

51. Equilibrium expression
Law of chemical equilibrium
For a reaction of the type
aA + bB  cC + dD
Equilibrium expression
Each set of equilibrium concentrations is called an equilibrium position.

52. Large values for K signify the reaction is “product favored”
When equilibrium is achieved, most reactant has been converted to product

53. Small values for K signify the reaction is “reactant favored”
When equilibrium is achieved, very little reactant has been converted to product

54. 2A + 3B  4C + 2D For the reaction:
Where K is the equilibrium constant, and is unitless

55. The Meaning of K
K > 1  the equilibrium position is far to the right
K < 1  the equilibrium position is far to the left