+ + A B A B A B A B S 8( s ) + O 2( g ) SO 2( g ) MnO 2 H 2 - - PDF document

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Chemical reactions

Evidence a chemical RXN has occurred:

• Color change
• Solid forms (precipitate)
• Gas is produced
• Heat generated

Chemical RXN:

• Rearrangement of atoms
• Atoms neither created nor destroyed

State subscripts

• (aq) - dissolved in water
• (s) -solid, precipitate
• (g) -gas
• (l) -liquid

Classification of Chemical Reactions

H2O2 (l)

MnO2

• H 2O(l ) +O 2

(g)

Catalyst = substance that speeds up a reaction but is not consumed

A

+

B A B

• 1. Decomposition Reaction- one reactants yield

two or more products

General Types of Chemical Reactions

• 2. Synthesis Reaction- two or more reactants

yield one product

A

+

B A B

S8(s ) +O 2(g) SO 2(g)

2

A + B C B C A +

• one element replaces another element in a compound
• products are different element and different compound
• 3. Single Replacement Reaction-

a) Halogen replaces the ion of another halogen:

Cl 2(g) Cl 2(g) + NaI(aq) Cl 2(g) + NaI(aq) I 2(s) Cl 2(g) + NaI(aq) I 2(s) +NaCl (aq)

c) active metal replaces H in acid:

Zn(s) +HCl (aq)

d) very active metal replaces H in water:

Na(s) + HOH (l)

element element compound compound

Zn(s) +HCl (aq) ZnCl 2(aq) Zn(s) +HCl (aq) ZnCl 2(aq) + H 2(g) Na(s) + HOH (l) NaOH(aq) Na(s) + HOH (l) NaOH(aq) +H 2(g)

b) metal replaces another metal in a solution:

Zn(s) +CuSO 4(aq) Zn(s) +CuSO 4(aq) ZnSO 4(aq) Zn(s) +CuSO 4(aq) ZnSO 4(aq) + Cu(

S )

• 4. Double Replacement Reaction-

+

B+ C- C- A+ A+ D-

+

B+ D-

• Two cations of different compounds swap places
• Products are two different compounds

Zn(NO3)

2(aq) + Na2CO3(aq)

NaCl (aq) + AgNO 3(aq)

Aqueous compound Aqueous compound Aqueous compound precipitate

• a. Precipitation reaction- a precipitate forms

Neutralization reaction- acid + base yield salt and water

HCl (aq) + NaOH (aq)

NaCl (aq) + AgNO 3(aq) AgCl (s) NaCl (aq) + AgNO 3(aq) AgCl (s) + NaNO3(aq)

HCl (aq) + NaOH (aq) HO H(l ) HCl (aq) + NaOH (aq) HO H(l ) + NaCl (aq)

Aqueous acid Aqueous base Aqueous salt water

Zn(NO3)

2(aq) + Na2CO3(aq) NaNO 3(aq)

Zn(NO3)

2(aq) + Na2CO3(aq) NaNO 3(aq) + ZnCO3(s )

decomposition synthesis

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Single replacement Double replacement

• 5. Combustion-
• A reaction in which a C-containing compound is

reacted with molecular oxygen

• releases enough E to sustain a flame
• a. Complete: more than enough O2 present
• b. Incomplete: not enough O2 present

CH 4 + O2 CH 4 + O2 CO 2 + H2O CH 4 + O2 CO + H2O

Always add O2 as a reactant Insert two rxns here: One with methanol combusted in excess O2 Other with C2H2 in limiting O2 Sample problem

• 1. CaSO4 + 2 AgNO3→ Ca(NO3)2 + 2AgSO4
• 2. CaCO3 (s) → CaO (s) + CO2 (g)
• 3. 4 V (s) + 5 O2 (g) → 2 V2O5 (s)
• 4. Cl2 (g) + 2 NaBr (s) → 2 NaCl (s) + Br2 (g)
• 5. Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4
• 6. H2O (l) + Na2O (s) → 2 NaOH(aq)
• 7. KClO3 (s) → KCl (s) + 3 O2(g)
• 8. FeS (g) + 2 HCl (g) → FeCl2 (s) + H2S (g)

DR Decomp Synth SR SR Synth Decomp DR Na2S (aq)

Aqueous solution of sodium sulfide is mixed with a solution of aluminum chloride producing solid aluminum sulfide and aqueous sodium chloride

+ AlCl3 (aq) → Al2S3 (s) + NaCl (aq)

• 1. Write formulas

3 6 2

• 2. Balance
• 3. What type of chemical reaction

Double Replacement

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Aqueous solution of calcium chromate is mixed with a solution of silver nitrate producing solid silver chromate and aqueous calcium nitrate

CaCrO4 (aq) + AgNO3 (aq) → Ag2CrO4 (s)+ Ca(NO3)2 (aq)

• 1. Write formulas
• 2. Balance
• 3. What type of chemical reaction

Double Replacement 2 Aqueous solution of iron (III) chloride is mixed with solid copper producing solid iron and aqueous copper (II) chloride

FeCl3 (aq) + Cu (s) → Fe (s) + CuCl2 (aq)

• 1. Write formulas
• 2. Balance
• 3. What type of chemical reaction

Single Replacement 2 3 3 2 “solid metal” = metal is element not ion Cu(s) not Cu+2 Mg(s) not Mg+2 diatomic elements= H O F Br I N Cl Cl2 not Cl O2 not O H2 not H