Lab 5

Single Replacement Reactions

Procedures

• Four different metals were added to hydrochloric acid solution

• Magnesium reacted immediately with rapid bubbling until the metal completely dissolved.

• Zinc reacted with slow bubbling.• Aluminum reacted much slower. Only reacting

with the 3.0 MHCl.• Copper did not react at all, regardless of the

length of time.

Single Replacement Reactions

• Single Replacement Reactions occur when one element replaces another in a compound.

• A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-).

• element + compound product + product A + BC AC + B (if A is a metal) ORA + BC BA + C (if A is a nonmetal)

(remember the cation always goes first!)

When H2O splits into ions, it splits intoH+ and OH- (not H+ and O-2 !!)

Single Replacement Reactions

• The metal only replaces hydrogen when the metal is more active than hydrogen.

• Magnesium , zinc and aluminum must be more active than hydrogen, since they replace hydrogen in the acid

• Copper must be less active than the hydrogen, since it does react with the hydrogen in the acid.

Analysis of the Single Replacement Reaction

REACTANTS PRODUCTS

Mg(s) + HCl (aq) MgCl2(aq) + H2(g)

Atoms held in fixed positions by metallic bonds

H+ and Cl- ions in solution by ion-dipole attractions

Mg2+ & Cl-

ions in solution by ion-dipole attractions

H atoms sharing a pair of e- in nonpolar covalent bonds

12 p

12 e-

1 p 17 p

0 e- 18 e-

12 p 17 p

12 e- 18 e-

1 p 1 p

1 e- 1 e-

Oxidation and Reduction

Oxidation Half-reactionMg atoms Mg2+ ions 12 p 12 p

12 e- 10 e- 0 +2 charge

Each magnesium atom lost two electrons

Mg Mg2+ + 2 e-Notice the reaction is balanced for protons and

electrons on both sides.

Oxidation and Reduction

Reduction Half-reactionhydrogen ions hydrogen molecules

1 p 1 p0 e- 1 e-

+1 0 chargeEach hydrogen ion gained an e- to form a hydrogen

atom, then two hydrogen atoms get together to share a pair of electrons

2e- + 2 H+ (aq) H2(g)

Notice the reaction is balanced for protons and electrons on both sides.

LEOLEO the lion says the lion says GERGER!!oossee

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Oxidation and Reduction

Equations to Summarize the Reaction

Molecular equationMg(s) + 2 HCl (aq) MgCl2(aq) + H2(g)

Total Ionic EquationMg + 2H+(aq) + Cl-(aq) Mg2+(aq) + Cl-(aq) + H2(g)

Net Ionic EquationMg + 2 H+(aq) Mg2+(aq) + H2(g)

Single Replacement Reactions

Activity Series of Metals Each element on the list replaces from a compound any of the elements below it. The larger the interval between elements, the more vigorous the reaction. The first five elements (lithium - sodium) are known as very active metals and they react with cold water to produce the hydroxide and hydrogen gas. The next four metals (magnesium - chromium) are considered active metals and they will react with very hot water or steam to form the oxide and hydrogen gas. The oxides of all of these first metals resist reduction by H2. The next six metals (iron - lead) replace hydrogen from HCl and dil. sulfuric and nitric acids. Their oxides undergo reduction by heating with H2, carbon, and carbon monoxide. The metals lithium - copper, can combine directly with oxygen to form the oxide. The last five metals (mercury - gold) are often found free in nature, their oxides decompose with mild heating, and they form oxides only indirectly.

lithium potassium strontium calcium sodium

-------------------------------magnesium aluminum

zinc Chromium

-------------------------------- iron

cadmium cobalt nickel

tin Lead

-------------------------------- HYDROGEN

antimony arsenic bismuth Copper

-------------------------------- mercury

silver palladium Platinum

gold