Chapter 10 Chemical Reactions Chemistry 1 – Notes #2b Chapter 10 Chemical Reactions

10.1 Reactions and Equations Chemical Reaction – process by which atoms are rearranged to form different substances. How do you know when a chemical reaction has occurred? Evidence temperature change color change odor bubbles (gasses are being formed) solid forming

Representing Chemical Reactions Reactant – starting substances Products – substances formed during reaction Symbol Meaning + Separate two or more reactants or products = “reacts with” Separates reactants from products = “to produce” (s) Identifies solid state (l) Identifies liquid state (g) Identifies gaseous state (aq) Identifies water soluntion

Representing Chemical Reactions reactant1 + reactant2 product1 + product 2 word equations: iron(s) + chlorine(g) iron(III)chloride(s) skeleton equations Fe(s) + Cl2(g) FeCl3(s) Practice page 279

Balancing Chemical Reactions Law of conservation of mass Steps for balancing are on page 281 in the textbook (Metals First, then non-metals, save H & O for last) Only Use coefficients for balancing equations Balancing Equations is like solving a puzzle

10.2 Classifying Chemical Reactions 5 types of chemical reactions Synthesis Combustion Decomposition Single Replacement Double Replacement some reactions may fit into more than one category

Synthesis Two or more substances react to produce a single product. A + B  AB These are some examples: K + Cl2 ---> KCl N2 + H2 ---> NH3 CaO + H2O ---> Ca(OH)2

Combustion Oxygen combines with a substance and releases energy in the form of light The reactions can also be classified as one of the other types of reactions. These are some examples: C + O2 ---> CO2 (also synthesis) 2H2 + O2 ---> 2H2O (also synthesis) CH4 + 2O2 ---> CO2 + 2H2O (also replacement)

Decomposition A single compound breaks down into two or more elements or new compounds Decomposition of water often requires an energy source AB  A + B These are some examples: 2 H2O ---> 2 H2 + O2 2 NaN3 ---> 2 Na + 3N2

Single Replacement Atoms of one element replace the atoms of another element in a compound A + BX  AX + B These are some examples: 2 Li + 2 H2O ---> 2 LiOH + H2 Cu + 2 AgNO3 ---> 2 Ag + Cu(NO3)2 See Fig 10-10 on page 288

Double Replacement An exchange between two compounds AX + BY  AY + BX Double Replacement: Evolution of a Gas When a solid is produced during a chemical reaction in solution, the solid is called a precipitate These are some examples: Ca(OH)2 + 2 HCl ---> CaCl2 + 2H2O 2 NaOH + CuCl2 ---> 2 NaCl + Cu(OH)2 See Table 10-2 on page 290

10.3 Reactions in Aqueous Solutions Vocabulary to Know Solution – homogeneous mixture Solute – a substance dissolved in a solution Solvent – the substance that dissolves a solute to form a solution Aqueous solution – a solution in which the solvent is water.

2NaOH(aq) + CuCl2(aq)  2NaCl(aq) + Cu(OH)2 (s) Complete ion equation – equation that shows all of the particles in a solution as they realistically exist. 2Na+(aq) + 2OH-(aq) + Cu2+(aq) + 2Cl-(aq) 2Na+(aq) + 2Cl-(aq) +Cu(OH)2(s) Spectator ions – ions that do not participate in the reaction Net ionic equation becomes 2OH-(aq) + Cu2+(aq)  Cu(OH)2(s)

Double-displacement reactions in aqueous solutions Reactions that form precipitates write the complete ionic and net ionic equations for KI(aq) + AgNO3(aq)  KNO3(aq) + AgI(s) Reactions that form water HBr(aq) + NaOH(aq)  H2O(l) + NaBr(aq) Reactions that form gases 2HI(aq) + Li2S(aq)  H2S(g) + 2LiI(aq)