Chapter 8-Equations

1. Learn the mechanics of writing an equation.

2. Learn how to identify four different kinds of reactions.

3. Learn how to predict the products of each kind of reaction and write the formulas of those products.

4. Given potential reactants, write the equation for the probable reaction.

Table 8-1, p. 204

Fig. 8-1a, p. 203

Fig. 8-1b, p. 203

Fig. 8-1c, p. 203

Fig. 8-1d, p. 203

Fig. 8-2, p. 203

Fig. 8-3, p. 203

Fig. 8-4, p. 203

Fig. 8-5, p. 204

Fig. 8-6, p. 204

Na reacting with water (indicator added)

Fig. 8-7, p. 205

Table 8-2, p. 205

Chemical EquationsDepict the kind of reactants and products

and their relative amounts in a reaction.4 Al(s) + 3 O2(g) f 2 Al2O3(s)The numbers in the front are calledstoichiometric coefficientsThe letters (s), (g), and (s) are the physical

states of compounds.

Chemical Equations4 Al(s) + 3 O2(g)

f 2 Al2O3(s)

This equation means4 Al atoms + 3 O2

molecules f 2 “molecules” of Al2O34 moles of Al + 3 moles of

O2 f

Reaction of Phosphorus with

Notice the stoichiometric coefficients and the physical states of the reactants and products.

Reaction of Iron with Cl2

Notice the stoichiometric coefficients and the physical states of the reactants and products.

Chemical Equations1.Because the same atoms

are present in a reaction at the beginning and at the end, the amount of matter in a system does not change.

2.The Law of the Conservation of Matter

2HgO(s) f 2 Hg(liq) + O2(g)

PLAY MOVIE

Because of the principle of the conservation of matter,

an equation must be balanced.

It must have the same number of atoms of the same kind on both sides.

Chemical Equations

Lavoisier, 1788

Balancing EquationsDO: Balance the equation entirely by using

coefficients placed before the different chemical formulas.

DON’T: Change a correct chemical formula in order to make an element balance, and do NOT add extraneous substances.

Balancing Equations

___ Al(s) + ___ Br2(s) f ___ Al2Br6(s)

PLAY MOVIE

p. 208

p. 209

p. 209

p. 211

p. 211

Balancing Equations

____C3H8(g) + _____ O2(g) f _____CO2(g) + _____ H2O(g)

____B4H10(g) + _____ O2(g) f ___ B2O3(g) + _____ H2O(g)

PLAY MOVIE

More examples

Table 8-3, p. 223

Combination ReactionReactants may be elements or compounds

pp. 213, 214

Combination ReactionReactants may be elements or compounds

1.2H2(g) + O2(g) 2H2O(l)

3.C(s) + O2(g) CO2(g)

5.2Na(s)+ Cl2(g) 2NaCl(s)

7.H2O(l) + CO2(g) H2CO3(aq)

Fig. 8-9, p. 212

Reaction of Phosphorus with

Notice the stoichiometric coefficients and the physical states of the reactants and products.

Decomposition Reaction

pp. 214, 216

Decomposition Reaction

1.2HgO(s) 2Hg(l) + O2(g) (heated)

3.CaCO3(s) CaO(s) + CO2(g) (heated)

5.2H2O(l) 2H2(g) + O2(g) (electrolysis)

Fig. 8-12, p. 214

Fig. 8-14, p. 216

Fig. 8-13, p. 215

Single Replacement Reaction

pp. 218, 220

Single Replacement Reaction

Reactants: Usually element (A) plus a solution of either an acid or an ionic compound (BX)

Products: Usually an ionic compound (in solution) (AX), plus an element (B)

A + BX → AX + B

Single Replacement Reaction

1.2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

3.Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g)

5.Cu(s) + 2AgNO3(aq)Cu(NO3)2(aq) + 2Ag(s)

Fig. 8-15, p. 218

Fig. 8-16, p. 218

Fig. 8-17, p. 219

Double Replacement Reaction(Switch Ions)

pp. 220, 223

Double Replacement Reaction

Reactants: Generally solutions of two substances that form ions in water

Products: Generally, two new compounds which are a solid, water, an acid, or an aqueous ionic compound

Reaction usually forms a precipitate (solid) or is a neutralization reaction between acid and base

AX + BY → AY + BX

Double Replacement Reaction1.NaCl(aq) + AgNO3(aq) NaNO3(aq) + AgCl(s)

3.NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)» (HOH)

4.H2SO4(aq) + Ba(OH)2(aq) BaSO4(s) + 2H2O(l)

6. (Acids have H+ and simple bases have OH-)

Fig. 8-18, p. 221

Table 8-3, p. 223

NOTE

1.Not all reactions will fit neatly into these 4 categories.

2.There are other types of reactions as well.3.This is just a simple classification system

to help you recognize certain patterns when first looking at chemical equations.