Chemistry Review THIS SLIDE SHOW INCLUDES MANY OF

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 k. L), 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 m. L), multiply by 1000 To change from mg (or mm or m. L) to g (or m or L), divide by 1000 Remember: 1 g = 1000 mg 1 km = 1000 m You should also know that 1 cm 3 = 1 m. L

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 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: NH 4+, SO 4 -2, SO 3 -2, NO 3 -1, NO 2 -1, PO 4 -3, CO 3 -2, OH-1, C 2 H 3 O 2 - 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 H 2 O) 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. H 2 SO 4 = 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 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 92 U = 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! H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 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 88 g CO 2 = 2 moles

On use the mole wheel: Multiply WITH the arrows; Divide AGAINST them 22. 4 L 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 show the ACTUAL number of atoms of each element Empirical formulas show the RATIO of the elements to one another. EX: C 4 H 8 is a molecular formula (C: H = 4: 8 which can be reduced to 1: 4) CH 4 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, HNO 3, H 2 SO 4, HCl. O 3 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!

Le. Chatlier’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!!!