ACS Review• Quick refresher of materials• Some sample questions and short cuts

Sections in ACS prep book to review

• Atomic Structure• Molecular Structure and bonding• Stoichiometry• States of Matter/ Solutions• Energetics• Descriptive Chemistry/ Periodicity• Laboratory Chemistry

Basics

• Dimensional analysis is very very important– Know how to make conversions

• cent, kilo, ect.• Grams moles (MM)• Vol grams (density)• Vol moles (concentration)

The periodic table

Notation and Calculation

Fe5626

Remember this?26 protons30 neutrons26 electrons

Calculations: you may need to do weighted averages. 20% of a sample is 32grams/mol and 80% 28grams/mol what is the average?

20x32 + 80x28 /100 = 28.8g/mol

The table• Which has the highest electronegativity?• Which is isoelectric to X?• Which is likely to form the same structure as __ ?• What has 25 protons?• If it has 24 neutrons and a mass of 52 what is the

element?

formulas

Example: you can’t remember if Ag has a +1 or +2 charge.if AgCl is a formula given in the question or in

some other question, knowing Cl is -1 tells you Ag is +1

Even more useful, use formula to determine charge.

Example: the correct formula for the compound formed between Al and S?

Al+3 and S-2 Al2S3

Know how to use charges to determine formula

Formulas from %

• Given mass % or total mass of each element determine empirical formula.A sample contains 11.1% H and 88.9% O

11.2grams H (1 mol/1.001g)=moles H88.9grams O(1 mol/16.0g)=moles O

=11.18=5.55

21

H2O

Reactions

• Single• Double• Composition• Decomposition• Combustion• Acid / Base

• Balance equationsknow difference in– General– Ionic– Net ionic

• stoichiometry

Acid base theories• Bronsted/ lowry• Lewis• Arrhenius

• Protons• electron pairs• What’s produced in water

You should have your six strong acids and bases memorized.

HCl, HBr, HI, HNO3, H2SO4, HClO4

LiOH, NaOH, KOH, CaOH2, SrOH2, BaOH2

Why?a) It helps identify weak acids and weak basesb) It will help with determining solubility

• Grams------mole------mole------gram• Amt------mole------mole-----amt• Amt -------- Mole

– Grams (molar mass)– Liters of solution (concentration)– Gas (Ideal gas law)

Yields•Balance equations

•Use stoichiometry

•Limiting reagents

Solution

solution of Lmole

•Molarity(M) Vs Molality(m)

solvent of Kgmole

Total solution solvent and solute Solvent only

Dilution: C1V1=C2V2

Titration:naMaVa=nbMbVb

Gas laws

• PV=nRT– Mostly the relationships (when P goes from 10-

20, V does what?)• Remember T is in K

– When gases are non ideal (correct for molecular volume and intermolecular forces)

– Diffusion small things faster

Structure

• Quantum numbers– n is the major shell(1,2,3…– l is the subshell (0=s, 1=p)– ml is the axis (x, y, z)– s spin (+ ½ )

• Filling the orbital (use the table)

Bonding and geometry

• Ionic vs. Covalent• Electronic vs. Molecular geometry (VSEPR)

– Drawing Lewis structures– Dipoles– Hybrids– Pi bonds– MO– Delocalized bonds (resonance)

Lewis structures• Multiple Choice Test Just be able to pick the

correct drawing!!• Some things to look for

– Octets on non-central atoms (all atoms if central is 1st row)– Happy elements– Charges

• Negative usually carried by single bonded O (one for each charge)• Positive usually carried by a four bond N or P

P

O

O

O

O

-3

N OO

Cl

N

H

H

H

H

+1

Cl

O

O

O

O

-1

States of matter

Gas

Solid

Liquid

Triple point

Freezing / melting

Condensing / boiling

Sublimation / Deposition

Know the basic properties

Remember this:

energy

– Heat of formation ( to form from the elements)Hf of MgCl2 is Mg(s) + ½ Cl2(g) MgCl2 H=___kJ

– Heat of combustion(react with O2)H of CH4 is CH4 + 2O2(g) CO2 + 2H2O H=___kJ

State function have which means final - initial

Solid at STP Diatomic gas at STP

EnergyBond Enthalpy = Sum of bond energy of reactants - sum of bond energy of products

(Breaking bonds- forming bonds)Enthalpy of reaction using DHf= sum of

products – sum of reactantsHess’s Law===Get to the goal by

manipulating reaction information given and adding up the reactions used

When Solving Problems

• Look for the easiest way to solve! There are 70 questions and only 110 minutes so THERE MUST BE SHORT CUTS!

1. Which of these compounds contains the greatest percentage of nitrogen?A) C6H3N307

B)   CH4N20C)   LiNH2 D)   Pb(N3)2

 

C6H3N307 229 g/molCH4N20 60.1 g/molLiNH2 23.0 g/molPb(N3)2 229.1 g/mol

The long way: calculate the %N for each one

The quicker way: all N have the same mass so, Which has the highest N to mass ratio or Even better which has the lowest total mass per N A cursory glance tells us it is not B or A D has 6 N it may need a second look 229/6=38

The answer is C

100mass total

N mass x

The Number of atoms in 9.0g of Aluminum is equal to the Number of atoms in A)   8.1g MgB)   12.1g MgC)   9.0g MgD) 18.0g Mg

The Long way:Calculate # of atoms in 9.0 g AlThen calculate mass of that # of Mg atoms

Look for ratios: Al has a molar mass of 27This is 1/3 of a mole Al

Which one is 1/3 mole of Mg

24.3 x 1/3 = 8.1g

So “A”

When NF3 and BF3 are reacted together they form BF3NF3

what is the geometry of the B and N atoms.A) Both tetrahedralB) B is triganal planer and N is tetrahedralC) Both triganal planerD) N is triganal planer and B is tetrahedral

How many things are around each?

B and N each will have 4 bonds

Both tetrahedral

A student wants to prepare a 250mL sample of 0.10 M NaCl. Which procedure is the most appropriate?

Molar mass of NaCl 58.4 g ·mol-1

A)    Add 5.84g NaCl to 250mL of waterB)    Add 1.46g of NaCl to 250mL of waterC)    Dissolve 5.84g of NaCl in 50mL and Dilute to 250mLD)    Dissolve 1.46g of NaCl in 50mL and Dilute to 250mL

Mol/L of solution

So A and B are out¼ L of 0.1M

5.84 is 0.1 mole NaCl

1.46 is ¼ of that So “D”

The oxidation number of chlorine in KClO3 isa) +6b) +5c) -1d) -2e) +2

O only oxidation is –2 (unless peroxide)

K only oxidation +1

3 x -2 = -6

1 x +1 =+1

-5

B+5 to Balance it out

Which one of the following sets of quantum numbers is not allowed?a) n = 3, l = 2, ml = +1b) n = 3, l = 3, ml = 0c) n = 3, l = 0, ml = 0d) n = 4, l = 3, ml = -2

l must be less than n

B

ml absolute value must be less than or equal to l

Which ion has 26 electrons?

a) Cr+2

b) Fe+2

c) Ni+2

d) Cu+2

Its really asking “Which is iso-electronic to Fe?”

On the table “What minus 2 electrons looks like iron?”

C Ni+2

Element X has two isotopes 13X with 80% abundance and 12X with 20% abundance, what is the average mass of the element?

a) 12. amub) 12.8 amuc) 12.5 amud) 13.0 amu

Long way: (13 X 80) + (12 X 20)/100

But why bother:the weighted average will be closer to the larger abundance

B

GOOD LUCK!!!

• 10 AM class your final is Friday April 27 at 8 am in LCTR 346

• 11 AM class your final is Monday April 30 at 8 am in LCTR 346

• You must get permission to switch from one time to another.

SI sessions and Office Hours

• SI sessions in RHSC 317 Tuesday at 5 pm and Wednesday 8 pm

• Offices Hours—– Wednesday (April 25th)11-4– Thursday (April 26th) 11-4– Sunday (April 29th)12-3