1. Gases Review

2. Things to remember about gases
Calculations:
Density (D)= m/V, thus m= Dx V, for gases V is in Liters, m is still in g!
Molar mass MM=dRT/P
PV=nRT
You can use PV=nRT to solve for Charles’ Boyles and other gas laws. Cross out what is constant!
Ptot= PA +PB +PC …
Pgas= Ptot-PH2O, when you collect GAS over WATER

3. More calculations: Rms = √3RT/MM Graham’s law of diffusion
Rate1 = √MM2
Rate2 √MM1
PA= χA Ptot
χA= mols A/total moles in system
- Smaller MM gases effuse faster and diffuse faster than larger MM gases

4. More things about gases
Ideal gases act more “real” at low temp and high pressure because the molecules are close together so IMFs matter.
You MAY have to use a chart or graph to get some of the data you need to solve a problem… be aware!
If you are given PP of water vapor, you will have to use it!

5. More things about gases
Kinetic Molecular Theory:
All gases are in constant motion
All gases have completely elastic collisions
Gases don’t have IMFs
Gases average kinetic energy is the same at the same temperature

6. Relationships between variables:
1) When P goes up, V does this???
2) When Temp goes up, V does this???
3) How do moles affect P???
4) Can you use moles interchangeably with P???

7. Things to KNOW in general:
Percent error= |actual-experimental| x 100
actual
Percent errors you want to be LOW
Percent yield= actual x 100
theoretical
Percent yields you want to be HIGH
How do you find actual???
How do you find theoretical?

8. Stoichiometry Review BE able to do the following:
Go from gram of a reactant to grams of a product. (either chart or dimensional analysis)
Go from moles of a reactant to moles of a product.
Go from grams or moles of a reactant to grams/ moles of another reactant. WHY? WHEN?

9. Stoichiometry Review KNOW THESE TO GET TO MOLES: g/MM M x Vin L
Atoms or molecules / x 1023
Gas at STP only: V/22.4

10. Stoichiometry Review
Recognize limiting reactant problems!!!! MOST OF THE TIME THEY WILL NOT TELL YOU IT’S LIMITING REACTANT!
So, how do you know?
Be able to solve for moles given volume and molarity.
KNOW MOLARITY COLD!!!! What is the definition of molarity?

11. Stoichiometry Review
Be able to calculate percentages! Part/whole x 100
Be able to use percentages to find out info in problem! For example: your actual yield is 89% of your theoretical yield….
How can you make a solution? STEP BY STEP
What if you start from g… what if you start from a solution?
Why do you ALWAYS add conc acid to water when diluting? Never water to conc acid!

12. Stoichiometry Review
Use the dilution equation to dilute solutions: Mdil Vdil =Mconc Vconc
You will only need to solve for 1 variable!
Know the mass spec idea. Why do we use it?
Understand how to solve for problems in which you make something…. Lab problems! Gravimetric analysis

13. Stoichiometry Review Beer’s Law: abc= A Where: a= molar absorptivity
b= path length of cell (usually 1 cm)
c= concentration
A= absorbance
Why do we need beer’s law???? We can use the absorbance of light to determine concentration when compared against a calibration curve!

14. Stoichiometry Review What is a calibration curve????
- A set of measurements that includes points before and after the points you are interested in…
Example: percent of sugar by mass of soft drinks…. You can create a calibration curve…

15. Types of Chemical Reactions
1) Synthesis… how do you know?
You start with 2 elements or an element and compound or two compounds…. BUT you make 1 product:
Examples:
Metal oxides + water  metal hydroxides
Metal hydrides + water  metal hydroxide + H2
Group I metal + water  metal hydroxide + H2
Element + element  compound
Nonmetal oxide + water  acid

16. Types of Chemical Reactions
Synthesis:
metal oxide + CO2  metal carbonate
Combustion:
Hydrocarbons or alcohols + O2  H2O + CO2
Hydrocarbons have only H and C
Alcohols have H, C and O only!

17. Types of Chemical Reactions
2) Decomposition
How do you know?
You start with one compound!!!!! ALWAYS!
To know:
H2O2  O2 + H2O (not balanced)
Metal hydroxides metal oxide + H2O
Acids nonmetal oxide + H2O

18. Types of Chemical Reactions
3) Single replacement:
How do you know??
Start with an element and a compound.
Cation replacement:
Switch the free metal with the one in the compound!
Ex: Zn + HCl  H2 + ZnCl2 (not balanced)
Anionic replacement:
Switch the halogens!
Ex: Cl2 + NaBr  NaCl + Br2 (not balanced)

19. Types of Chemical Reactions
4) Double Replacement
How do you know? You start with 2 ionic compounds!
What is the goal of double replacements??? To form a precipitate, a gas or a weak acid
How do you know if it is a gas? Here are the common ones: CO2, SO2, SO3, NO2, NO, NH3

20. Types of Chemical Reactions
How do you know if it precipitates?
SOLUBILITY RULES:
Know this…. If it has a group 1 metal in the compound, it is soluble!
If it has a nitrate in the formula, it is soluble!
If it is soluble, it DOES NOT form a precipitate!
If it is a strong acid, it will always ionize! (SOLUBLE!) What are they????

21. For those of you that really care:
Halides (group 17) are mostly soluble except: Pb, Ag, and Hg
Sulfates are soluble except: Ca, Sr, Ba Pb
Hydroxides are only soluble with group 1 and Ca, Sr, Ba (a little)
Phosphates are NOT soluble
Sulfides are NOT soluble