# AS tudent want to prepare 250mL of .10 MN aCl solution which is by DlLc8588

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```									   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
56            Remember this?
26   Fe
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
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
Know how to use charges to determine
formula
Example: the correct formula for the compound formed
between Al and S?
Al+3 and S-2  Al2S3

Even more useful, use formula to
determine charge.
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
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 =11.18   2   H2O
88.9grams O(1 mol/16.0g)=moles O =5.55      1
Reactions
•   Single               • Balance equations
•   Double                 know difference in
•   Composition            – General
– Ionic
•   Decomposition
– Net ionic
•   Combustion
• stoichiometry
•   Acid / Base
Acid base theories
• Bronsted/ lowry           • Protons
• Lewis                     • electron pairs
• Arrhenius                 • 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 bases
b) It will help with determining solubility
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)
Solution
•Molarity(M) Vs Molality(m)

mole                                mole
L of solution                       Kg of solvent
Total solution solvent and solute           Solvent only

Dilution:                          Titration:
C1V1=C2V2                          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

O                   O -1                   O
-3              H    +1
N    O         O Cl O                 O     P    O              H N H
Cl                   O                      O                         H
States of matter
Know the basic properties
Remember this:
Freezing / melting
Liquid

Solid

Condensing / boiling

Gas

Sublimation / Deposition

Triple point
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
Solid at STP      Diatomic gas at STP

State function have D which means final - initial
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
Hess’s Law===Get to the goal by
manipulating reaction information given and
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) CH4N20
C) LiNH2                   C6H3N307 229 g/mol
CH4N20    60.1 g/mol
D) Pb(N3)2                 LiNH      23.0 g/mol
2
Pb(N3)2   229.1 g/mol

The long way: calculate the %N for each one          mass N
x100
total mass
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 Number of atoms in 9.0g of Aluminum is equal to the
Number of atoms in
A) 8.1g Mg
B) 12.1g Mg The Long way:
C) 9.0g Mg Calculate # of atoms in 9.0 g Al
D) 18.0g Mg 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”
When NF3 and BF3 are reacted together they form BF3NF3
what is the geometry of the B and N atoms.
A) Both tetrahedral
B) B is triganal planer and N is tetrahedral
C) Both triganal planer
D) 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 water
B) Add 1.46g of NaCl to 250mL of water
C) Dissolve 5.84g of NaCl in 50mL and Dilute to 250mL
D) Dissolve 1.46g of NaCl in 50mL and Dilute to 250mL

Mol/L of solution
¼ L of 0.1M
So A and B are out
5.84 is 0.1 mole NaCl
So “D”
1.46 is ¼ of that
The oxidation number of chlorine in KClO3 is
a) +6
b) +5
c) -1
d) -2
e) +2

O only oxidation is –2 (unless peroxide)   3 x -2 = -6
K only oxidation +1                        1 x +1 =+1
-5

+5 to Balance it out      B
Which one of the following sets of quantum numbers is not
allowed?
a) n = 3, l = 2, ml = +1
b) n = 3, l = 3, ml = 0
c) n = 3, l = 0, ml = 0
d) n = 4, l = 3, ml = -2

l must be less than n
ml absolute value must be less than or equal to l

B
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. amu     Long way: (13 X 80) + (12 X 20)/100
b) 12.8 amu
c) 12.5 amu    But why bother:
d) 13.0 amu    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

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