27/11/2012 Chapter 4: Aqueous Reactions and Solution Stoichiometry.
Electrolytes: substances that dissociate into ions when dissolved in water.
• A non-electrolyte may dissolve Ina after, but it does not dissociate into ions when it does so.
Electrolyte and Non- Electrolyte
• Soluble ionic commands tend to be electrolytes
• Molecular compounds tend to be non-electrolytes, except for acids and bases.
• A strong electrolyte dissociates completely when dissolved in water
• A weak electrolyte only dissociates partially when dissolved in water.
Strong electrolytes are...
• 1. Strong acids
• 2. Strong bases
• 3. Soluble ionic salts.
• When one mixes ions that form compounds that are insoluble( as could be dedicated by the solubility guidelines) a precipitate is formed.
Metathesis ( Exchange) Reactions
• Metathesis comes from the Greek word that means " to transpose"
• It appears the ion in the reactant compounds exchange, or transpose, ions.
• AgNO3( aq) + KCL(aq) ~ AgCl(s) + KNO3(aq)
• The molecular equation lists the reactants and products in their molecular formula
Net Ionic Equation
• To from the net ionic equation, cross out any things that doesn't change from the left side of the equation to the right
• The only things left in the equation are those things that change during the course of the reaction
• Those things that didn't change and were deleted from the net ionic equation they are called spectator ions.
Writing Net Ionic Equations
1. Write a balanced molecular equation
2. Dissociate all strong electrolytes
3. Cross out anything that remains unchanged from the left side to the right side of the equation
4. Write net jet ionic equation with the species that remain
There are only seven strong acids.. All have a charge of negative one
• Hydrochloric HCl
• Hydrobromic HBr
• Hydroiodic HI
• Nitric HNO3
• Sulfuric. H2SO4
• Cholric. HCLO3
• Perchloric. HCLO4
The strong bases are the soluble salts of hydroxide ion
• Alkali metals
• Observe the reaction between milk of magnesia Mg(OH)2 and HCL
Oxidation - Reduction reactions
• An oxidation occurs when an atom or ion loses electrons
• A reduction occurs when an atom or ion gains electrons
• One can not occur with out he other.
• To determine if an oxidation- reduction reaction has occurred, we assign an oxidation number to each element in a neutral compound or charged entity.
• Elements in their element to have negative form have an oxidation number of 0
• The oxidation number of a monatomic ion is the same as its charge.
Non metals tend to have negative oxidation numbers although some are positive in certain compounds or ions.
Oxygen has an oxidation number of -2 except in the peroxide ion in which it has an oxidation number of -1
Hydrogen is -1 when bonded to a metal +1 when bonded to a non metal
Fluorine always has an oxidation number of -1
The other halogens have an oxidation number of -1, when they are negative, they can have positive oxidation numbers, however, most notably in oxyanions
The sum of the oxidation numbers in a neutral compound is 0
The sum of the oxidation numbers in a poly atomic ion is the charge on the ion
• In this reaction silver ions oxidize copper metal.
Cu (s) + 2 Ag (+) (aq) -----------> Cu (+2) (aq) + 2 Ag (s)
The reverse reaction doesn't occur.
• Two solutions can contain the same compounds but quite different because proportions of those compounds are different
• Molar it's is one way to measure the concentration of a solution
• Molarity (M) = moles of solute / volume of solution in liters.
Titration:The analytical technique in which one can calculate the concentration of the solute in a solution
Thermo chemistery chapter 5
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