Chemistry – Jan 25, 2017 P3 Challenge – Balance this reaction: _____N2O5 + _____H2O  _____HNO3 Today’s Objectives – Word Equations and Types of Reactions

Chemistry – Jan 25, 2017 Objective – Word equations Types of Reactions Assignment: Balancing Reactions Worksheet (finish) Unit 4 Retest on Monday, Jan 30 Agenda Homework Review Write equations from word descriptions Nomenclature Review 5 types of reactions

Word Equations Word equations are written in English. You must convert the English to a balanced chemical equation with the appropriate state descriptors. Beware: Solids and aqueous solutions can be described with many different words. Think about it. Visualize it, and choose your label. Be careful. YOU MUST WRITE THE CORRECT FORMULA FOR EACH SUBSTANCE NAMED. If your reaction doesn’t balance, double check your formulas, and try again. (Note: This is not balancing by changing subscripts, though it may feel like it. This is correcting an error that has been identified.)

Word Equations Examples When solid sodium metal reacts with liquid water, an aqueous solution of sodium hydroxide and hydrogen gas are formed. When aqueous calcium chloride and aqueous sodium sulfate are mixed a white solid of calcium sulfate forms in an aqueous solution of sodium chloride. The reaction of aqueous silver nitrate and aqueous sodium chromate that forms solid silver chromate and aqueous sodium nitrate.

Types of reactions Synthesis (Combination) Decomposition A + B  AB Two elements react to form a compound Decomposition AB  A + B A compound is separated into its elements Single Replacement A + BC  AC + B One element takes the place of another in a compound. Double Replacement AB + CD  AD + CB Ionic partners switch

Combustion The reaction with oxygen is so common that it is often given its own classification: combustion. The products of a combustion are always the oxides of the elements in the other reactant. If there is a choice of metal ion, you will be told what ion charge to use. Ex: Fe + O2  Fe2O3 Ex: CH4 + O2  CO2 + H2O Ex: Li + O2  Li2O Classify each of the reactions from previous slides.

Balancing practice _____ H2 + _____ O2  _____ H2O _____ Fe + _____ Cl2  _____ FeCl3 _____ Cu + _____ AgNO3  _____ Cu(NO3)2 + _____ Ag _____ Zn + _____ HCl  _____ ZnCl2 + _____ H2 _____ Pb(NO3)2 + _____ AlCl3  _____ PbCl2 + _____ Al (NO3)3 _____ LiClO3  _____ LiCl + _____ O2 _____ Mg(OH)2 + _____ HCl  _____ MgCl2 + _____ H2O

Reaction Types Overview Reactants Reaction Type Products Two elements Synthesis (S) Compound of the two elements A single compound Decomposition (D) Component elements (or simpler substances) An element and a compound Single replacement (SR) Different element and compound Two compounds Double replacement (DR) Two different compounds Reaction with oxygen Combustion (C) Oxides of each element in other reactant

Exit Slip - Homework Exit Slip: Balance the following chemical equation: _____Pb(NO3)2  _____PbO + _____NO2 + _____O2 Then identify it’s type with a S, D, SR, DR, or C. What’s Due? (Pending assignments to complete.) Complete the Balancing Reactions Worksheet (pages 1 and 2 only without the types.) – Due Wednesday, Feb 1 Unit 4 Retest on Monday, Jan 30 What’s Next? (How to prepare for the next day) Read p263-285