ACS Review

1
ACS Review

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

2
Sections in ACS prep book to review

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

3
Basics

• Dimensional analysis is very very important
• Know how to make conversions
• cent, kilo, ect.
• Grams ? moles (MM)
• Vol ? grams (density)
• Vol ? moles (concentration)

4
The periodic table
5
Notation and Calculation
Remember this?
26 protons 30 neutrons 26 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
6
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?

7
formulas
Know how to use charges to determine formula
Example the correct formula for the compound
formed between Al and S?
Al3 and S-2 ? Al2S3
Even more useful, use formula to determine charge.
Example you cant 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
8
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 H 88.9grams O(1
mol/16.0g)moles O
11.18
2 1
H2O
5.55
9
Reactions

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

• Balance equations
• know difference in
• General
• Ionic
• Net ionic
• stoichiometry

10
Acid base theories

• Bronsted/ lowry
• Lewis
• Arrhenius

• Protons
• electron pairs
• Whats 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?
• It helps identify weak acids and weak bases
• It will help with determining solubility

11
(No Transcript)
12
Yields

• Balance equations
• Use stoichiometry
• Limiting reagents

• Grams------mole------mole------gram
• Amt------mole------mole-----amt
• Amt -------- Mole
• Grams (molar mass)
• Liters of solution (concentration)
• Gas (Ideal gas law)

13
Solution

• Molarity(M) Vs Molality(m)

Total solution solvent and solute
Solvent only
Dilution C1V1C2V2
Titration naMaVanbMbVb
14
Gas laws

• PVnRT
• 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

15
Structure

• Quantum numbers
• n is the major shell(1,2,3
• l is the subshell (0s, 1p)
• ml is the axis (x, y, z)
• s spin ( ½ )
• Filling the orbital (use the table)

16
Bonding and geometry

• Ionic vs. Covalent
• Electronic vs. Molecular geometry (VSEPR)
• Drawing Lewis structures
• Dipoles
• Hybrids
• Pi bonds
• MO
• Delocalized bonds (resonance)

17
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

18
States of matter
Know the basic properties
Remember this
19
energy

• Heat of formation ( to form from the elements)
• DHf of MgCl2 is Mg(s) ½ Cl2(g) ? MgCl2
  DH___kJ
• Heat of combustion(react with O2)
• DH of CH4 is CH4 2O2(g) ? CO2 2H2O DH___kJ
• State function have D which means final - initial

20
Energy

• Bond 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 reactants
• Hesss LawGet to the goal by manipulating
  reaction information given and adding up the
  reactions used

21
When Solving Problems

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

22
Which of these compounds contains the greatest
percentage of nitrogen?A) C6H3N307B)   CH4N20C
)   LiNH2 D)   Pb(N3)2 
C6H3N307 229 g/mol CH4N20 60.1
g/mol LiNH2 23.0 g/mol Pb(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 229/638
The answer is C
23
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
Al Then calculate mass of that of Mg atoms
Look for ratios
Al has a molar mass of 27
This is 1/3 of a mole Al
Which one is 1/3 mole of Mg
24.3 x 1/3 8.1g
So A
24
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
25
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-1A)    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
So A and B are out
5.84 is 0.1 mole NaCl
So D
1.46 is ¼ of that
26
The oxidation number of chlorine in KClO3 isa)
6b) 5c) -1d) -2e) 2
O only oxidation is 2 (unless peroxide)
3 x -2 -6
K only oxidation 1
1 x 1 1
-5
B
5 to Balance it out
27
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
ml absolute value must be less than or equal to l
B
28

• Which ion has 26 electrons?

• Cr2
• Fe2
• Ni2
• Cu2

Its really asking Which is iso-electronic to Fe?
On the table What minus 2 electrons looks like
iron?
C ? Ni2
29
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 amu d) 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
30
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.

31
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