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 !!