Chemical Reactions

Chemical Reactions Chemical Change reorganization original substances form new substances with different formulas may or may not involve a change of state symbols used to describe chemical substance reaction are known as a chemical equation Chemical equations do not have equal signs (=) they have an arrow Chemical Equations Must follow the Law of Conservation of Matter atoms thunder mug neither be created or destroyed during a chemical reaction What goes in must come out Chemical Equations Reactants = Products same number of atoms of apiece element on each lieu of the reaction arrow Equations must be balanced other symbols (s)solid (l)liquid (g)gas (aq)aqueous, dissolved inwater Balancing Chemical Equations First incorporate all ionic formulas to see if they are correct Five steps to balancing equations 1. Count the number of atoms of each element (or polyatomic ion) on the reactant side and then on the product side. You may want to use a chart or table. 2. Determi ne which are out of balance these need to be balanced 3.Pick an element or polyatomic ion to start with Balance using coefficients. Do not use coefficients of 1 No changes may be made to the subscripts use least common multiples 5. Check and recheck Practice balancing these equations H2(g) + O2(g) H2O KCl + BaSO4 K2SO4 + BaCl2 Types of Chemical Reactions Combination /Direct Combinationsynthesis 2Na(s) + Cl2(g) 2 NaCl(s) Single Displacement angiotensin converting enzyme substitution anion always replaces anion cation always replaces cation Mg + 2 HCl MgCl2 + H2 Complete the following Single Displacement (formula is correct) Al + CuSO4 divalent Displacement 2 substitutions ion-exchange MgSO4 + BaCl2 BaSO4 + MgCl2 Types of Chemical Reactions Double Displacement What are the expected products of MgSO4 + BaCl2 Types of Chemical Reactions KOH + MgCl ( check formulas and complete) Decomposition HgO Hg + O2 (balance) 2 HgO 2 Hg + O2 carbonic acid in lab pr actise Oxidation / Reduction oxidize iron into rust 4Fe + 3O2 ( 2Fe2O3 Oxidation reactions add O (or remove H) Reduction reactions add H ( or remove O) oxidation-reduction reaction Combination of oxidation and reduction Practice How many grams of diatomic oxygen (O2) are needed to make 4 moles of magnesium oxide (MgO) from magnesium decoration (Mg)? Hint balance equation and use coefficient as mole. Energy in a Chemical Reaction Endothermic heat in requires activation button A + B + 100kcal = C + D Exothermic heat out A + B = C + D + 100 kcal