UNIT 8: Formulas and Equations

AIM# 1: How can we distinguish between quantitative and qualitative information? Chemical Symbols: Each element has a unique one-, two-, or three- letter symbol The first letter is always capitalized (Table S, PT) Almost all symbols are written without a subscripts as monatomic Diatomic Molecules: elements that exist in nature as two identical atoms covalently bonded into a diatomic molecule Br2, I2, N2, Cl2, H2, O2, F2

Chemical Formulas: compounds are composed of elements chemically combined in fixed ratios Formulas use chemical symbols and number to show both qualitative and quantitative information about a substance Qualitative: information that relates to things that cannot be counted or measured- What elements are in the compound Quantitative: information that deals with things that can either be counted or measured The number of atoms of each element in the compound (subscript or coefficient can give us this info)

Empirical: simplest ratio Molecular: actual ratio Ionic formulas are always empirical formulas Molecular: actual ratio covalently bonded substances form molecules, in some cases the empirical represents both empirical and molecular –H2O- In other cases molecular formula is a multiple of the empirical formula C6H12O6 – six times the empirical CH2O

AIM: How can we distinguish between quantitative and qualitative information? Example: Determine the quantitative and qualitative information in the following examples: CaCO3 Zn3(PO4)2

AIM # 2: How can we know what elements form a compound and in what proportions? Atoms and compound are electrically neutral – equal numbers of negative (electrons) and positive (protons) Ions Cations are positive Anions are negative Polyatomic Ion: group of atoms covalently bonded together, possessing a charge Table E

Forming a compound: By attraction of oppositely charged ions Monatomic or polyatomic ions attract each other in a ratio that produce a neutral compound Coefficients: written in front of a formula, applies to entire formula, multiply the coefficient and subscript to determine the number of each type of element

Hydrates are compounds that contain definite amounts of water molecules Ex: BaCl2·2H2O – Barium chloride traps 2 water molecules

*** Remember compounds must be neutral *** For many elements, the oxidation state is equal to the charge found in the top right corner of each element box 1:1 Na+ & Cl - yields NaCl Mg2+ & S2- yields MgS Not 1:1 – Mg2+ & Cl - Write the charge of one ion as the subscript of the other without the sign (# only) Thus MgCl2; that is 1 Mg with a 2+ & 2 Cl with 1- each yields (2+) + 2(1-) = 0

Examples: Write the formulas for the following: a. Al+3 and Br – b. Ba+2 and CO3 -2 c. Cu 2+ and CO3 -2 d. Pb +2 and Cl – e. Pb +4 and CrO4 -2

AIM # 3: How can we name compounds? Binary Ionic (Metal–positive & Nonmetal–negative) 1st element (metal) – retains its name 2nd element (nonmetal) – change ending to “ide” Ex: KCl is Potassium chloride Other Ionic (Contains Polyatomic Ions) Same as Binary except all polyatomic ions retain their name Examples: KNO3 is __________________ NH4Cl is _____________________ NH4NO3 is___________________ Potassium nitrate Ammonium chloride ammonium nitrate

Examples: Write the names for the following formulas: a. Mg(SO4) b. Na(OH) c. Ca(OH)2 d. Li3(PO4) e. (NH4)Cl

Nitrogen monoxide Dinitrogen tetroxide Iron (II) chloride Covalent (2 Nonmetals) Need prefixes to tell reader how many of each Exception – if only one 1st element, don’t use mono Examples NO is _____________________ N2O4 is _____________________ Stock System (multiple oxidation states) Examples are Iron, Tin, Copper (mostly transition metals) a Roman numeral proceeding the metal tells the reader the oxidation number FeCl2 is _________________ FeCl3 is _________________ Nitrogen monoxide Dinitrogen tetroxide Iron (II) chloride Iron (III) chloride

BINARY ACIDS: composed of H and one other elements (TABLE K) Naming Acids BINARY ACIDS: composed of H and one other elements (TABLE K) Ex) HCl - hydrogen chloride Name begins with hydro followed by the name of other element with modified ending – ic Ex) HCl – hydrochloric acid

TERNARY ACIDS: Have polyatomic ions containing O – table E 1.Anion suffixes – ate and – ite usually replaced by –ic and – ous respectively -ate to –ic -ite to –ous Examples) HNO3 -> NITRIC ACID H2SO4 -> SULFURIC ACID

AIM # 4: What are the different parts of a chemical equation and how can we use this to demonstrate the law of conservation? Reactant(s) yield Product(s) Reactant are on the left of the arrow (yield sign) and products are to the right of the arrow State of matter is indicated by the letter inside the parenthesis Example: C (s) + O2 (g) → CO2 (g) Identify the reactants and products in the equation above…….

Review of chemical reactions (we already know this!!) Endothermic Heat is required for a reaction to occur, thus, energy is found on the reactant side Example: H2O (s) + energy → H2O (l) Exothermic Heat is produced in a reaction, thus energy is found on the product side Example: H2O (g) → H2O (l) + energy

BALANCING The Law of Conservation of Mass & Charge must be upheld Example: __ H2 (g) + __ O2 (g) → __ H2O (g) “T chart method” Remember – It’s coefficient x subscript to find the # of atoms 2 1 2

Nothing can be created or destroyed – law of conservation of mass Count up the atoms on both side and fill in any missing elements or compounds Same thing for missing mass Practice: If 103.0g of potassium chlorate are decomposed to form 62.7g of potassium chloride and oxygen gas according to the equation 2KClO3  2KCl + 3O2 how many grams of oxygen are formed?

AIM: What are the different types of chemical reactions? Synthesis 2 or more reactants form 1 product A + B → AB Decomposition 1 reactant breaks down into 2 or more products AB → A + B Single Replacement 1 element replaces another A (element) + BX (compound) → B (element) + AX (compound) Double Replacement 2 elements/polyatomic ions replace two others AB (compound) + CD (compound) → AD (compound) + CB (compound)

AIM: How can we predict products of a chemical reactions? Single Replacement Reactions: If the individual metal is above the metal that is in the compound a reaction will occur Double Replacement Reactions: If a solid is formed (Table F) If a gas is formed If a molecular substance such as water is formed

Using TABLE F Soluble Insoluble NH4Cl  MgOH Cross out the first element or compound Look for second element or compound on Table F check to see if it is paired with an exception Determine solubility Ex) NH4Cl  MgOH Soluble Insoluble

TABLE F AgNO3(aq) + NaCl(aq)  AgCl(_____) + NaNO3(____) s aq

AIM: How can we determine an unknown reactant, product, or mass in a chemical equations? Nothing can be created or destroyed – law of conservation of mass Count up the atoms on both side and fill in any missing elements or compounds Same thing for missing mass