Download - Review final
CHEM 111REVIEW SESSION
FALL 2011 STELLA KRITIKOU
SECTIONS 480, 517, 556
BASIC THINGS YOU NEED TO KNOW FOR MOST EXPERIMENTS
MAKE SURE YOU STUDY & REVIEW
BASIC THINGS FROM CHEM 101
SUCH AS
Moles / Molarity / Molecular Weight
Bond types / Valence Electrons
Electronegativity / Lewis Structures
Chemical reactions / Reaction types
HOW TO CALCULATE THE NUMBER OF MOLES
If you have a solution (therefore the volume and the molarity/concentration of the solution is known)
Where C: the molarity/concentration of you solution (mol/L)
n: the number of moles (mol)
V: the volume of the solution in L (L)
If you have a solid compound (therefore the mass and the molecular weight is known)
Where n: the number of moles (mol)
m: the mass of your solid
Mw: the molecular weight of your solid
C n
V n CV V
n
C
n m
MW
m MWn
They might as well ask you something more complicated:
Calculate the number of moles in 50g of HCl
solution, if d=1.048 kg/L and C=6M.
From the density I know that I have 1.048 kg HCl
per Liter. Notice that kg/L is the same as g/mL
Hence I can calculate the volume of my solution:
d m
V V
m
d V
50gHCl
1.048gHClmLHCl
V 47.71mLHCl
Now you have the Volume and the Molarity and
you can calculate the number of moles.
DON’T FORGET TO CHANGE THE VOLUME IN L!
47.71mLHCl 47.71mLHCl1000mLHCl
LHCl 0.04771LHCl
C n
V n CV N 6
molHClLHCl
0.04771LHCl 0.28626molHCl
Calculate the number of moles in 50g of 10% w/w HCl solution.
Step 1:
The HCl solution is 10% w/w,
meaning that in 100 kg (or g) of the solution
I have 10 kg (or g) of HCl acid.
Therefore my solution contains:10gHCl100gSolution
50gSolution 5gHCl
Step 2:
Now you have the mass of the HCl acid (5g) and
you can easily calculate the Molecular weight:
Step 3:
Now you are ready to calculate the number of
moles:
MW AW (H ) AW (Cl)1 35.45 36.45gHClmolHCl
n m
MW
n 5gHCl
36.45gHClmolHCl
n 0.137molHCl
Now.. Let’s move on to the main subject!
Experiments / Exercises
The chemistry of recycling
The graphical depiction of Scientific Data
Acid Base Chemistry
Project 2 (cations, anions and unknown)
Enthalpy determination
Gas Laws
Scientific Literature
From Atoms to molecules
Chemistry of Recycling
Balance chemical equations
Write net ionic equations
Write total ionic equations
Figure out the type of the reaction
Calculate the theoretical yield
Calculate the percent yield
Graphical Depiction of Scientific Data
You should be able to determine what type of chart you should use every time
Remember:
in chemistry, we don’t use pie charts and bar/column charts
often, because it is common to have correlation between the
quantities measured.
You should be able to tell if the trendline given represents the data accurately or not (and how this reflects on the R-squared value)
You should be able to tell the relationship between two quantities, when the graph (with or without the trendline) is given
Acid-Base ChemistryYou should know the most common acids and bases that we used in the Lab. (eg you should know that NaOH is a base and HNO3 is an acid etc)
Different types of titration
The importance of the indicator and the difference between the final and the equivalence point
Review the mustard experiment
Project 2 : Determination of an unknown ionic compound
FROM PART I (CATIONS)You should remember the most obvious (and easy) things in the lab. For example that K+
didn’t precipitate at any point, or that Cu2+ had the easiest flame test or that Zn+ is the only amphoteric one.
Remember that the tests are based on the differences in solubility between the cations
You should remember the two different elimination tests that we performed & the confirmation test (flame test)
FROM PART II (ANIONS)
You should remember the most obvious (and easy) things in the lab. For example that Cl-
didn’t dissolve at any point.
Remember that the confirmation tests are different for each anion this time
You should remember the two distinct branches of the logic tree
FROM PART III (UNKNOWN)
You should remember that the first thing you had to do was to dissolve your compound
You should be able to figure at least one reason for getting a false positive or negative result in ANY case.
IN GENERAL
They might give you a logic tree and observations and ask you to follow down the tree.
They might give you a list with observations and ask YOU to draw the logic tree
You should be able to go from data to logic tree and back
Enthalpy Determination
Energy neither created or destroyed
Closed or open system
Heat flow of a system
Enthalpy of a chemical reaction
Memorize the basic relationships
MAKE SURE YOU KNOW HOW YOU DEFINE THE SYSTEM AND HOW YOU DEFINE THE SURROUNDINGS EVERY TIME
Heat flow & Molar enthalpy change
First Law of Thermodynamics
q mc
0 qPn
quniverse qsystem qsurroundings 0
qsurroundings qsystem
Gas Laws: P, V, T Ideal Gas Law
P = Pressure
V = Volume
n = number of moles
T = Temperature
R = ideal or universal Gas Constant
MAKE SURE YOU USE THE SAME UNITS EVERYWHERE AND YOU USE THE CORRECT VALUE FOR R (ACCORDING TO THE UNITS)
PV nRT
From the Ideal Gas Law you can determine EVERYTHING! (REALLY E V E R Y T H I N G!!!)
Therefore you should know the relationship between
Pressure and VolumePressure and TemperatureVolume and Temperature
What happens to a system when you heat it up? (Consider the kinetic energy of the system)
How can you calculate one of them when you are given the rest of them?
How can you calculate one of them GRAPHICLY?
It is possible that they will combine this experiment with exercise 2.
You might be given different graphs and asked to calculate something or to determine the relationship between the two quantities.
You might be asked whether a given graph can accurately describe the relationship between two quantities.
Scientific Literature Make sure you know what Peer-Reviewed Sources are.
Make sure you know how to read a reference
Author(s)
Title
Year or date of the publication
Title of the journal where it was published
Volume and number (or issue) where the article was printed
Page number
From Atoms to Molecules
Find the number of Valence electrons each time
Consider the charge of the molecule (if any)
Draw a “draft” Lewis structure
Consider the electronegativity of each one of the atoms
Assign partial charges accordingly
Figure out the molecular geometry
Draw a final Lewis structure (don’t forget the total charge!)
Consider if there is an overall dipole or not
Remember if a molecule is more likely to intercalate or bind to DNA
A word of advice! Don’t pull an all-nighter the day BEFORE the exam. It’s not helpful if you’re sleepy!
Don’t assume that your exam will be the same as the day before, because it WON’T
If you have absolutely NO CLUE about a problem don’t try to guess; however if you know how to approach the problem but you don’t know how to get to the final answer go for it!
Eat something sweet before taking your exam (you think it’s not working but .. It’s chemistry!)
Good luck !!