F ORMULA M ASS, M OLECULAR M ASS, & P ERCENT C OMPOSITION

F ORMULA M ASS The total mass of an ionic compound Sum of the masses of all atoms Remember- subscripts tell how many of each atom is in the compound! Ex: NaCl= (1 x amu)+ (1 x amu)= amu

M OLECULAR M ASS Mass of a molecular compound Process for calculating molecular mass is the same as for ionic compounds Ex: H 2 O= (2 x amu) + (1 x amu) = amu

P RACTICE Determine the mass of the following compounds: CO 2 MgCl 2 KI BH 3

P ERCENT C OMPOSITION Percentage by mass of each element in a compound Mass of element x 100 = % composition of mass of compound element

E XAMPLE % composition of O in CO 2 : CO 2 = (1 x amu) + (2 x amu)= amu 2 O atoms in CO 2, which weigh a total of amu (16.00 x 2) amu x 100 = 72.71% amu

P RACTICE What is the percent composition of H in H 2 O? What is the percent composition of Li in Li 2 O?

Chemical Equations and Reactions

What is a chemical reaction? process by which one or more substances are changed into one or more different substances Two parts: reactants and products Described by chemical equations – Provide symbols, identities, and amounts of each substance

Indicators that a reaction occured Production of heat and/or light Production of a gas Formation of a precipitate Color change

SymbolMeaning “Yields”; indicates result of reaction Reaction is reversible (s) A reactant or product in the solid state; also used to indicate a precipitate Indicates a precipitate (l) A reactant or product in the liquid state (aq) A reactant or product in an aqueous solution (dissolved in water) (g) A reactant or product in the gaseous state Indicates a gaseous product Δ or heat Reactants are heated 2atm Pressure at which reaction is carried out pressure Pressure at which reaction is carried out exceeds normal atmospheric pressure 0°C Temperature at which reaction is carried out MnO 2 Formula of catalyst used to alter the rate of the reaction

Type of ReactionDefinitionGeneral FormulaExample Equation Synthesis (composition) Two or more substances combine to form a new compound A + B  ABNa (s) + Cl (g)  NaCl (s) Decomposition A reactant decomposes to form two more products AB  A + B 2H 2 O (l) electricity 2H 2(g) + O 2(g ) Single Replacement (Single Displacement) One element replaces another element in a compound A + BC  AC + B (metal replacing another metal) X + BY  Y + BX (nonmetal replacing another nonmetal) Mg (s) + 2HCl (aq) → H 2(g) + MgCl 2(aq ) Cl 2(g) + 2KBr (aq) → 2KCl (aq) + Br 2(l) Double Replacement (Double displacment) Ions from two compounds switch places in an aqueous solution to form new compounds AB + CD  AC + BD 2KI (aq) + Pb(NO 3 ) 2(aq) → PbI 2(s) + 2KNO 3(aq) Combustion Hydrocarbon combines with oxygen to form carbon dioxide and water C x H y + O 2(g)  __CO 2(g) + H 2 O (l) C 3 H 8 + 5O 2(g)  3CO 2(g) + 4H 2 O (l)

Turn to page 271 in Textbook Complete problems 25,26,27,28, and 29 Due TODAY! TURN IN WITH SUB.

B ELL R INGER 10 Match the equation with the type of reaction. 1. Na 3 PO KOH  3 NaOH + K 3 PO 4 2. C 6 H O 2  6 CO H 2 O 3. CaCO 3  CaO + CO 2 4. Pb + FeSO 4  PbSO 4 + Fe 5. P O 2  2 P 2 O 3