““Chemical Chemical Reactions”Reactions”

All chemical reactions…All chemical reactions… have two parts:have two parts:

1.1. ReactantsReactants = the stuff you start = the stuff you start withwith

2.2. ProductsProducts = the stuff you end up = the stuff you end up withwith

The reactants will turn into the The reactants will turn into the products.products.

Reactants Reactants Products Products

Reactants

Products

Label Reactants and Label Reactants and ProductsProducts

Ca(OH)Ca(OH)22 + 2HF + 2HF 2H2H22O + CaFO + CaF22

Label Reactants and Label Reactants and ProductsProducts

Ca(OH)Ca(OH)22 + 2HF + 2HF 2H2H22O + CaFO + CaF22

reactants products

In a chemical reactionIn a chemical reaction Atoms aren’t created or destroyed (based on Atoms aren’t created or destroyed (based on

the Law of Conservation of Mass)the Law of Conservation of Mass) A reaction can be described several ways:A reaction can be described several ways:

#1. #1. In a In a sentencesentence every item is a wordevery item is a word Copper reacts with chlorine to form copper (II) Copper reacts with chlorine to form copper (II)

chloride.chloride.

#2. #2. In a In a word equationword equation some symbols used some symbols used

Copper + chlorine Copper + chlorine copper (II) chloride copper (II) chloride

#3. In a #3. In a skeleton equationskeleton equation : use all : use all symbols but are not balanced.symbols but are not balanced.

#4. In a #4. In a balanced chemical equationbalanced chemical equation no words are used; only symbols. no words are used; only symbols.

CuCu(s) (s) + Cl+ Cl22(g) (g) CuClCuCl22s)s)

Symbols in equations? Symbols in equations? the arrow (the arrow (→) →) separates the reactants from separates the reactants from

the products the products (arrow points (arrow points toto products) products)

Read as: “reacts,” “forms” or “yields”Read as: “reacts,” “forms” or “yields” The plus sign is read as “and,” “is added The plus sign is read as “and,” “is added

to,” or “reacts with”to,” or “reacts with”

(s) after the formula = solid:(s) after the formula = solid: Fe Fe(s)(s)

(g) after the formula = gas:(g) after the formula = gas: CO CO2(g)2(g) (l) after the formula = liquid:(l) after the formula = liquid: H H22OO(l)(l)

Symbols used in equationsSymbols used in equations (aq) after the formula = an (aq) after the formula = an

aqueous solution: aqueous solution: NaClNaCl(aq)(aq) is a salt water solution is a salt water solution

(salt dissolved in water)(salt dissolved in water) used after a product = a gas has used after a product = a gas has

been been producedproduced: H: H22↑↑ used after a product = solid has used after a product = solid has

been been producedproduced: PbI: PbI22↓↓

Symbols used in equationsSymbols used in equations■ double arrow double arrow = a reversible = a reversible

reaction (more later)reaction (more later)

■ = heat is = heat is supplied to the reactionsupplied to the reaction

■ = a catalyst is used (in = a catalyst is used (in this case, platinum is the catalyst)this case, platinum is the catalyst)

heat ,

Pt

What is a catalyst?What is a catalyst? A substance that speeds up a A substance that speeds up a

reaction, without being reaction, without being changed or used up by the changed or used up by the reaction.reaction.

The Skeleton EquationThe Skeleton Equation Uses formulas and symbols to Uses formulas and symbols to

describe a reactiondescribe a reactionDoes not indicate how many; this Does not indicate how many; this

means the equation is NOT means the equation is NOT balancedbalanced

All chemical equations are a All chemical equations are a descriptiondescription of the reaction. of the reaction.

Write a Write a skeleton equationskeleton equation for: for:

Solid iron (III) sulfide reacts with Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form gaseous hydrogen chloride to form solid iron (III) chloride and solid iron (III) chloride and hydrogen sulfide gas.hydrogen sulfide gas.

FeFe22SS3 (s)3 (s) + HCl + HCl(g)(g) FeClFeCl3(s)3(s) + H + H22SS(g)(g)

Fe+3 S-2 H+1 Cl-1 Fe+3 Cl-1 H+1 S-2

Write a Write a skeleton equationskeleton equation for: for:

Nitric acid dissolved in water reacts with Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate and carbon dioxide gas and sodium nitrate dissolved in water.dissolved in water.

HNOHNO3(aq)3(aq) + Na + Na22COCO3(s)3(s) HH22OO(l)(l) + CO + CO2(g)2(g) NaNO NaNO3(aq)3(aq)

H+1 NO3-1

Na+1 CO3-2

H2OCO2

Na+1 NO3-1

Now, write a sentence for these Now, write a sentence for these equations:equations:

1. Fe1. Fe(s)(s) + O + O2(g)2(g) Fe Fe22OO3(s)3(s)

Solid iron reacts with oxygen gas to form Solid iron reacts with oxygen gas to form

solid iron (III) oxide.solid iron (III) oxide.

2. NO2. NO2(g)2(g) N N2(g)2(g) + O + O2(g)2(g)

Nitrogen dioxide gas breaks down to Nitrogen dioxide gas breaks down to

form nitrogen gas and oxygen gas.form nitrogen gas and oxygen gas.

1. sodium chloride + lead (II) nitrate lead (II) chloride + sodium nitrate

2. iron + chlorine iron (III) chloride

3. barium + water barium hydroxide + hydrogen gas

4. When chlorine gas reacts with carbon tetrahydride, carbon tetrachloride and hydrogen chloride are produced.

5. When sodium oxide is added to water, sodium hydroxide is produced.

6. In a blast furnace, iron (III) oxide and carbon monoxide gas react to form carbon dioxide gas and iron.

7. Iodine crystals react with chlorine gas to produce iodine trichloride.