Unit F: Chemical Reactions



Unit 6: Chemical Reactions

What is a Chemical Reactions?

Rxn Bkt p.2

Balancing Chemical Equations

1) Cannot change a subscript for a chemical formula

2) Can add a coefficient in front of a chemical formula

3) Coefficient multiplies the formulas’ number of atoms

2 Ca3(PO4)2: 6 Ca, 4 P, 16 O

4) Same number of atoms of each element on the reactants’

and products’ sides

Examples Hebden p.107-110

Exercises Heb p.110-112: even numbers, Rxn Bkt p.6#1

Converting Word Equation into Chemical Equation:

1) Use periodic table

Symbol and metal or non metal

2) Use naming concept map

Ionic, covalent or elemental

Ionic: metal + non metal ions

Use list of polyatomic ions (back of periodic table)

Covalent: non metal + non metal

3) Elemental: pure element Ex: Pb, Ni, Au

4) Hof Brincl: diatomic molecules (H2, O2, F2, Br2, I2, N2, Cl2)

5a) With an acid use:

When I ate it, it’s icky (sulphate---sulphuric acid)

When I bite it, it’s delicious( sulphite----sulphurous acid)

b) Acid with an element

Hydro + element + ic

Hydrochloric acid : HCl

6) Trivial names: (Common old names)

Ammonia: NH3

Acetic acid: CH3COOH

States and Symbols of Chemical Reactions

+: combining

( yielding or making

s, l, g, aq: solid, liquid, gas, aqueous (dissolved in water)

reactants ( products

Exercises: Heb p.113#57-64: odd numbers

6 Types of Chemical Reactions (Hebden p.114-118)

1) Synthesis (Velcro couple)

A + B ( AB

metal non metal metal ion/non metal ion

Ex: rusting a nail (as a product, iron is +3)

Fe(s) + O2(g) ( Fe2O3(s)

Nail iron (III) oxide

Balanced:

4Fe(s) + 3O2(g) ( 2Fe2O3(s)

2) Decomposition (Break up)

AB ( A + B

Ex: Decomposition of hydrogen peroxide (using a catalyst)

H2O2(l) ( H2O(g) + O2(g) (Remember Hof Brincl)

Balanced:

2H2O2(l) ( 2H2O(g) + O2(g)

3) Single Replacement (New kid in the block)

a) AB + C ( CB + A

metal metal metal metal

non metal non metal

Ex: Adding steel wool to copper(II) sulphate solution

Fe(s) + CuSO4 (aq) ( FeSO4 (aq) + Cu(s)

b) AB + C ( AC + B

metal non metal metal non metal

non metal non metal

Ex: CaF2 + Cl2 ( CaCl2 + F2

Activity Series: How do we use it? Rxn Bkt p.3

4) Double Replacement Cross over charges (switching partners)

AB + CD ( AD + CB

K2SO4 (aq) + AgNO3(aq) ( Ag2SO4(s) + KNO3(aq)

metal metal

non metal non metal

Using an ion box

K2SO4 (aq) + 2AgNO3(aq) ( Ag2SO4(s) + 2KNO3(aq)(Balanced)

5) Neutralization (special type of double replacement)

acid + base ( salt + water

ionic compound

H2SO4 + 2 NaOH ( Na2SO4 + 2 H2O

Sulphuric acid

6) Combustion of Hydrocarbons

hydrocarbon: contains hydrogen and carbon atoms

Reacting with oxygen gas

2 C8H18 + 25 O2 ( 16 CO2 + 18 H2O

octane

Exercises: Heb p.118#65-66

**T**Predicting the Products of a Reaction:

1) General Rules:

1) Find the chemical formulas for each reactant using:

i) Periodic table

ii) Naming concept map

iii) List of polyatomic ions (P.A.I)

2) Looking at the reactants, select the reaction type:

Synthesis, decomposition, combustion (O2), SR, DR, Neutralization

3) Find the relevant products and beware of:

(i) Hof Brincl

.Diatomic molecule by themselves (in pair)

.H2, O2, F2, Br2, I2, N2, Cl2

(ii) A metal is always mono-atomic (one atom) and uncharged

(iii) Ionic product: metal ion(cation) + non metal ion(anion)

2) Single Replacement Products:

i) Locate the substance that is replacing the ion in the compound

Metal ( cation+ (metal ion)

Non metal ( anion- (non metal ion)

ii) Locate both substance and ion in the Activity Series (Rxn Bkt p.3)

Substance on top can replace the other substance on the bottom

Ex 1: Magnesium bromide + chlorine ( ?

MgBr2 + Cl2 ( ?

Br2 < Cl2 Activity Series: Refer to Rxn Bkt p.3

Answer: MgBr2 + Cl2 ( MgCl2 + Br2

Ex 2: Rnx Bkt p.12#2

Aluminum + iron (III) oxide ( ?

Al + Fe2O3 ( ?

Al > Fe Activity Series: Refer to Rxn Bkt p.3

Balanced Equation:

2Al + Fe2O3 ( 2Fe + Al2O3

3) Double Replacement Products:

i) Set up an ion box containing cations and anions

ii) Insert cations and anions in the ion box

iii) Find the products by switching cations with anions

Ion Box

|Cation |Anion |Product |

| | | |

| | | |

Ex-1: silver nitrate + zinc chloride( ?

AgNO3 + ZnCl2 ( 2 ionic substances reacting (DR)

Ion box

|Cation |Anion |Product |

| | |(Criss cross) |

|Ag+ |NO3- |AgCl |

|Zn2+ |Cl- |Zn(NO3)2 |

2AgNO3 + ZnCl2 ( 2AgCl + Zn(NO3)2

Ex-2: Sulfuric acid + sodium hydroxide ( ?

H2SO4 + NaOH ( ?

Ion box

|Cation |Anion |Product |

| | |(Criss cross) |

|H+ |SO42- | H2O |

|Na+ |OH- | Na2SO4 |

H2SO4 + 2NaOH ( 2H2O + Na2SO4 (DR also neutralization rxn)

3) Hydrocarbon Combustion

Hydrocarbon: contains hydrogen and carbon (ex: C3H8)

Combustion: O2 as a reactant (oxygen molecule(Hof Brincl)

Products: carbon dioxide (CO2) and water (H2O)

Ex: butane combustion in a lighter

C4H10 + 13 O2 ( 4CO2 + 5H2O 1, 6.5, 4, 5

2 8 + 5 = 13 oxygen atoms

After multiplying the whole equation by two:

2C4H10 + 13 O2 ( 8CO2 + 10H2O 2, 13, 8, 10

Exercises: Heb p.118#67, Rxn Bkt p.6-8#2

Thermochemical Reactions

Def:Energy Changes in Chemical Reactions (Endo/Exo Chart Rxn Bkt p.4)

2 types of energy changes:

Exothermic(hot) or endothermic(cold)

Exo Rxn: Carbon Tree Reaction

(i) 2 C12H22O11(s) + 2 H2SO4(aq) + O2(g) (

22 C(s) + 2 CO2(g) + 24 H2O(g) + 2 SO2(g) + 400 kJ

Energy term is found as a product

(ii) 2 C12H22O11(s) + 2 H2SO4(aq) +O2(g)(

22 C(s) + 2 CO2(g) + 24 H2O(g) + 2 SO2(g) (H = -400 kJ

Endo Rxn: Smelling Salts

(i) 2 NH4SCN(s) + Ba(OH)2•8H2O(s) + 500kJ (

2 NH3(g) + 10 H2O(l) + Ba(SCN)2(aq)

Energy term is found as a reactant

(ii) 2 NH4SCN(s) + Ba(OH)2•8H2O(s) (

2 NH3(g) + 10 H2O(l) + Ba(SCN)2(aq) (H = 500kJ

Lab: Thermochemical Reactions

Exercises: Heb p.121#70-75, p.122#76-80, Rxn Bkt p.5, p.8#3

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download