Unit: Chemical Reactions Day 1 - Notes Unit: Chemical Reactions Diatomic elements, Writing formula equations from word equations Upper left: Thermite reaction, Fe2O3 + Al => 2Fe +2Al2O3 + HEAT!!! http://en.wikipedia.org/wiki/Thermite Upper right: potassium in water, K + H2O => KOH + H2 + HEAT Bottom right: potassium chlorate and sugar, C12H22O11 + 8KClO3 => 12CO2 + 11H2O + 8KCl + HEAT!!! http://lecturedemos.chem.umass.edu/chemReactions5_5.html Bottom left: magnesium reacting with oxygen, Mg + O2 => MgO

After today you will be able to… Name the diatomic elements Write formula equations given the word equation for a chemical reaction Balance the chemical equations Explain law of conservation of mass

STANDARD CLE 3221.3.3 Explore the mathematics of chemical formulas and equations. Use word problems to translate the names of chemical compounds and elements to chemical equations and balance the equations.

ESSENTIAL QUESTION How do mathematical relationships and experimental data relate to chemical formulas?

OBJECTIVE About 90% students can name the diatomic elements and write formula equations given the word equation for a chemical reaction

Complete the practice questions TASK Complete the practice questions

A chemical equation represents a chemical reaction. Reactants  Products “Yield” Reactants and products are separated from each other with a plus (+) sign.

Common forms of chemical reactions… A + B  C A  B + C A + B  C + D

Chemical equations can be written as word equations or formula equations. Formula/Skeletal equations can be balanced or unbalanced.

Word Equation: Iron + Oxygen  Iron (III) Oxide Formula Equation: 4Fe(s) + 3O2(g) 2Fe2O3(s) Balanced!

Symbols in Chemical Equations Meaning (s) Solid (l) Liquid (g) Gas (aq) Aqueous (dissolved in H2O)  Reversible reaction  or  Heat is added  Catalyst is added (A substance that speeds up a reaction.) heat Pt

To change word equations into formula equations follow the flow chart…

ELEMENT? Monatomic Diatomic Is the substance an… ELEMENT? Monatomic Diatomic Just write the symbol Example: “Sodium”=Na Br2 I2 N2 Cl2 H2 O2 F2 Have the subscript “2” Examples: “Bromine”=Br2 “Hydrogen” = H2

Is the substance a… COMPOUND? CaCl2 N2O4 Ionic Molecular (M +nM) (nM +nM) Balance charges!!! Example: “calcium chloride” Ca+2 Cl-1 Cl-1 Prefixes for subscripts Examples: “dinitrogen tetroxide” CaCl2 N2O4

Law of Conservation of Atoms: There must be the same number of each type of atom before the reaction as after the reaction.

Coefficients: Are numbers that go in front of each substance to indicate the number of atoms or molecules that are reacting or being produced.

Let’s try some examples! 

Helpful tip: Keep all substances and + signs in Examples: Convert into formula equations… 1. sodium chloride + fluorine  sodium fluoride + chlorine 2. aluminum + sulfur  aluminum sulfide Helpful tip: Keep all substances and + signs in line with each other! Na+1 Cl-1 Na+1 F-1 NaCl + F2  NaF + Cl2 Al+3 S-2 Al + S  Al2S3

+ Mg3(AsO4)2 ZnS  Zn3(AsO4)2 + MgS 3. zinc + magnesium  zinc + magnesium Zn+2 S-2 Mg+2 (AsO4)-3 Zn+2 (AsO4)-3 Mg+2 S-2 sulfide arsenate arsenate sulfide + Mg3(AsO4)2 ZnS  Zn3(AsO4)2 + MgS

If the numbers match on either side… You’re balanced! Examples: Balance the following equation: ___ Al + ___S  ___Al2S3 2 3 2 1 Al 2 3 1 S 3 If the numbers match on either side… You’re balanced!

___ Li + ___O2  ___Li2O Examples: Balance the following equation: 4 2 1 Li 2 4 2 O 1 2

Do not separate polyatomic ions! Examples: Balance the following equation: ___Fe2(SO4)3 + ___Na3(PO4)  ___Fe(PO4) + ___Na2(SO4) 2 3 Helpful tip: Do not separate polyatomic ions! 2 2 Fe 1 2 3 (SO4) 1 3 6 3 Na 2 6 1 (PO4) 2 1 2 YES!!!! Are we balanced?

Do now: practice questions Then: Begin WS 1