Chapter 7 Part II Notes

Determining Products of Reactions To predict the products for any equation, you must first determine Synthesis – Decomposition – Combustion –

Reaction Prediction 2 or more reactants and you’re told that there’s only one product = When writing the products, you must look at the charges of the ions. Example: Al(s) + Br2(l)  Example: Ca(s) + N2(g) 

Reaction Prediction 1 reactant = decomposition Remember the “7” diatomic molecules and Example: CCl4(l)  Example: Mg3N2(s) 

Reaction Prediction hydrocarbon (compound with C & H) + O2 = Example: CH4(g) + O2(g)  Example: C3H8O(g) + O2(g) 

More Examples C8H18 + O2  Ba(NO3)2  Mg + O2

Reaction Prediction Part 2 Single displacement – 1 element & 1 compound react Double displacement – 2 compounds react Neutralization – acid and base in the reactants

Reaction Prediction 1 element & 1 compound = In the products, you can’t have Example: Mg(s) + Zn(NO3)2(aq)  Example: Cl2(g) + KF(aq) 

Reaction Prediction 2 ionic compounds = Example: AgNO3(aq) + NaCl(aq)  Fe2(SO4)3(aq)+ Na3PO4 (aq)

Reaction Prediction 1 acid (starts with H) & 1 base (ends with OH) = Water gets rid of all hydrogen and hydroxide ions. Example: HCl(aq) + KOH(aq)  Example: Ca(OH)2(aq)+ H2SO4(aq)

More Examples

Solubility If a substance is an aqueous solution (aq), If a substance is insoluble, Insoluble substances form as the result of If a substance is slightly soluble or partially soluble in water,

Figure 7.3: Solubilities of common compounds.

Solubility Examples Ca(NO3)2 CuOH CaCl2 (NH4)2SO4 Zn3(PO4)2 FeCO3 SrO

Precipitation Reactions in all precipitation reactions, At least one of the products formed is KI(aq) + AgNO3(aq)  KNO3(aq) + AgIs K+ I- Ag+ NO3- Ag I 3

Dissociation Occurs in ionic compounds and acids when ionic compounds dissolve in water the anions and cations are separated from each other; this is called dissociation we know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity 4

Electrical conductivity of aqueous solutions Electrical conductivity of aqueous solutions. (a) Pure water does not conduct an electric current. (b) When an ionic compound is dissolved in water, current flows and the lamp lights.

Figure 7.5: When gaseous HCl is dissolved in water, each molecule dissociates to produce H+ and Cl- ions.

Dissociation potassium chloride dissociates in water KCl(aq) = K+ (aq) + Cl- (aq) copper(II) sulfate dissociates in water CuSO4(aq) = Cu+2(aq) + SO42-(aq) K+ Cl- K Cl Cu+2 SO42- Cu SO4 5

K2SO4(aq) = 2 K+ (aq) + SO42-(aq) Dissociation potassium sulfate dissociates in water K2SO4(aq) = 2 K+ (aq) + SO42-(aq) K+ SO42- K SO4 6

Process for Predicting the Products of a Precipitation Reaction Determine what ions Exchange Ions (+) ion from one reactant with (-) ion from other Balance Charges of combined ions to Balance the Equation count atoms Determine Solubility solubility rules if product is insoluble or slightly soluble, 7

Figure 7.1: The precipitation reaction that occurs when yellow potassium chromate, K2CrO4(aq), is mixed with a colorless barium nitrate solution, Ba(NO3)2(aq).

Figure 7.4: Precipitation of silver chloride occurs when solutions of silver nitrate and potassium chloride are mixed.

Example Problems Predict the products given each of the following reactants. Also denote which compound forms a precipitate: Cu(NO3)2(aq) + KOH(aq)  FeCl3(aq) + Mg3(PO4)2(aq)  NaBr(aq) + AgNO3(aq) 