Download Chemistry Review

Chemistry Review
THIS SLIDE SHOW INCLUDES
MANY OF THE CONCEPTS THAT
YOU NEED TO KNOW TO GET
STARTED ON A SUCCESSFUL
YEAR IN AP CHEMISTRY.
LEARN THEM! COME AND GET
HELP ON ANYTHING THAT YOU
DON’T UNDERSTAND.
Measurement
 Be sure you know:




To change from m (or g or L) to km (or kg or kL), divide by 1000
To change from km (or kg or L) to m (or g or L) , multiply by 1000
To change from g (or m or L) to mg (or mm or mL), multiply by 1000
To change from mg (or mm or mL) to g (or m or L), divide by 1000
 Remember:


1 g = 1000 mg
1 km = 1000 m
 You should also know that

1 cm3 = 1 mL
Sigfigs
 When multiplying or dividing, your answer can have
no more sigfigs than the smallest number of sigfigs
in the numbers you are working with.
 WHEN IN DOUBT, EXPRESS YOUR ANSWER
WITH THREE SIGFIGS. (The AP readers will allow
you one more or one fewer sigfig than you should
have; you are pretty safe if you keep three.)
Chemical Symbols
 Know them like the back of your hand!
 Be sure you write them correctly.
 SOME of the ones you should know:
 H, Li, Na, K, Fr, Be, Mg, Ca, Sr, Ba, Ti, Mn, Fe, Co, Ni, Pt, Cu,
Ag, Au, Zn, Hg, B, Al, C, Si, Sn, Pb, N, P, Bi, O, S, F, Cl, Br, I,
He, Ne, Ar, Kr, Xe, U
Atomic Structure
 Know the BASIC structure of the atom (we will get
into energy levels later.)
 In the nucleus:


Protons (charge of +1)
Neutrons (no charge)
 Outside the nucleus
 Electrons (charge of -1)
 An atom’s mass is the sum of the protons and
neutrons
 An atom’s atomic number (identity) is the number of
protons
Periodic Table
 Know the following:
 Column 1 – Alkali metals (charge of +1)
 Column 2 – Alkaline Earth Metals (charge of +2)
 Column 17 – Halogens (charge of -1)
 Column 18 – Noble Gases (inert – rarely form compounds)
 The stair step line separates the metals from non-metals
 The lanthanides and actinides are at the bottom (we’ll talk
about why later)
 Transition elements (metals) – Groups 3-12
Periodic Trends
 Learn these now (later we will talk about the WHYS)
 Atomic radius – increases going down, decreases going across
 Electronegativity – decreases going down, increases going
across
 Ionization energy – decreases going down, increases going
across
Polyatomic Ions
 Also know these like the back of your hand! You will
save yourself a lot of trouble later if you learn their
formulas AND charges now:

NH4+, SO4-2, SO3-2, NO3-1, NO2-1, PO4-3, CO3-2, OH-1, C2H3O2-
 There may be others that you will need to learn later,
but you will have a good start if you learn these.
Ionic and Covalent Compounds
 If a formula begins with a metal, it is most likely an
IONIC COMPOUND.

Formed when one atom gives electron(s) to another atom.
 If a formula begins with a non-metal, it is most likely
a COVALENT COMPOUND.


Formed when two or more atoms share electron(s) to give each
an octet.
Covalent compounds can also be called MOLECULAR (You
will hear me use these terms interchangeably.)
Naming Compounds
 To name ionic compounds, say the name of the first
element. Then say the name of the second element,
but change its end to IDE.
 To name covalent compounds, say the name of the
first element, adding a prefix to indicate the number
of atoms present (unless there is only one – then
don’t add the prefix.) Then do the same with second
element, again adding a prefix and ending the
element’s name with IDE.
Naming Acids
 If it begins with H, it is an acid (unless H2O)
 If there are 2 elements, it is a BINARY acid. Say
HYDRO, then the name of the SECOND element,
changing its end to IC. Then add the word acid.

HCl = Hydrochloric acid
 If there are 3 elements, it is a TERNARY acid. Say
the name of the MIDDLE element, changing its end
to IC. Then add the word acid.

H2SO4 = Sulfuric Acid
Naming Hydrocarbons
 If the compound contains ONLY hydrogen and
carbon, it is a hydrocarbon.
 Know these roots:






Mother Eats Peanut
1 carbon = meth
Butter!
2 carbons = eth
3 carbons = prop
4 carbons = but (pronounced byōōt)
5 carbons = pent
The rest are easy – hex, hept, oct, etc.
Writing Formulas
 KNOW how to do this! There should be NO
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


questions about writing formulas in AP chemistry!
Write the symbol for each element (or formula if it is
a polyatomic ion)
Determine the charge of each (you should know most
of them!)
CRISS-CROSS the charges.
IF (and only if) you add a subscript after a
polyatomic ion, you need to put the polyatomic ion
in parentheses.
Nuclear Notation
 Know how to interpret:
238
92U = uranium (atomic number 92) with 92 protons and an
atomic mass of 238. This means that THIS PARTICULAR atom
of uranium has 92 protons and 238-92= 146 neutrons. (238
THINGS or NUCLEONS in the nucleus.) Remember that only
protons and neutrons have mass, so an atom’s mass is the sum of
the things in the nucleus.
Remember that the atomic mass on the periodic table is the
AVERAGE of all of the isotopes of an element. It is not a whole
number because it is an AVERAGE.
Diatomic Molecules
 LEARN THE SPECIAL SEVEN NOW!
 H2, N2, O2, F2, Cl2, Br2, I2
 How to find them on the periodic table:
 Find H – that’s the first one. Then go to NUMBER 7
(nitrogen). From there draw a seven and you will have the
others – nitrogen, oxygen, fluorine, chlorine, bromine, iodine.
 LEARN THEM NOW!
Molar Mass
 Look at a formula and list the elements
 Count the atoms of each element
 Look up the atomic mass (on the periodic table) of
each element.
 Multiply by the number of atoms
 Add everything up.
 YOU WILL NOT NEED TO WRITE EVERYTHING
DOWN FOR LONG – YOU WILL SOON BE ABLE
TO DO THESE QUICKLY ON YOUR CALCULATOR.
Moles to grams and Grams to moles
 Start by using dimensional analysis, but you
probably won’t need to do that all year.
 To change grams to moles, divide by molar mass
 To change moles to grams, multiply by molar mass
 88g CO2 = 2 moles
 On use the mole wheel:
 Multiply WITH the arrows; Divide AGAINST them
22.4L
gram
Mole
6.02 x 1023
% Composition
 Find molar mass
 Divide the mass of each element by the total molar
mass
 Multiply results by 100 to get %
Empirical and Molecular formulas
 Molecular formulas show the ACTUAL number of
atoms of each element
 Empirical formulas show the RATIO of the elements
to one another.
 EX:
 C4H8 is a molecular formula (C:H = 4:8 which can be reduced
to 1:4)
 CH4 is its empirical formula (C:H = 1:4)
Finding Empirical Formulas
 Change % to grams
 Change grams to moles
 Divide by smallest number of moles to get a ratio
 If necessary, multiply everything by the same
number to get a whole number ratio.
 LEARN THIS POEM:
% to grams
Grams to moles
Divide by small
Times ‘til whole
Molecular formulas
 Once you find an empirical formula, you may be




given a molar mass and asked to find a molecular
formula
Find the molar mass BASED ON THE EMPIRICAL
FORMULA.
Divide it into the given molar mass
Take the number you get and multiply all subscripts
in the empirical formula.
The results is the molecular formula
Acids and Bases
 Bronstead Lowry definition: (you’ll learn other
definitions later)


Acid –proton donor
Base – proton acceptor
 For now, you should know that acids begin with H
and bases end with OH.
 It is H+ (hydrogen ion or proton) that gives an acid
its properties.
 It is OH- (hydroxide ion) that gives a base its
properties.
Strong Acids and Bases
 Completely dissociate in water (break down into
ions)
 HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3
 Hydroxides of the alkali metals are strong bases.


Hydroxides of the alkaline earth metals are strong bases
EXCEPT the ones at the top of the column. (Be(OH)2 and
Mg(OH)2 are weak.
Calcium hydroxide is weird! Some books call it weak and some
books call it strong. You will get credit either way!
SOLUBILITY RULES
 LEARN THESE! You will use them all year.
 All salts of alkali metals are soluble
 Nitrates are always soluble
 Ammonium salts are always soluble
 Acetate salts are always soluble
 Chlorates and perchlorates are always soluble
 Salts of chlorine, bromine, and iodine are soluble EXCEPT
with silver, mercury, lead (the heavy bad guys)
 Sulfates are soluble EXCEPT with silver, mercury, lead,
calcium, strontium, barium
 EVERYTHING ELSE is INSOLUBLE!
 LeChatlier’s Principle:
 If a change is imposed on a system at equilibrium, the position
of the equilibrium will shift in a way to reduce the effect of that
change.
 AB + CD  AD + CB
 If more CD is added, the reaction will shift RIGHT to produce
more AD and CB (get rid of the extra CD)
 If some CB is removed, the reaction will shift RIGHT to
produce more (will cause LESS AB and CD to be present)
 Writing equilibrium expressions:
 AB + CD  AD + CB
 K = [AD][CB]
[AB][CD]
The value of K tells us how much
of the product is formed. BIG K =
a lot of product. LITTLE K = small
amount of product.
WATER and SOLIDS are never part of equilibrium
expressions!!!