CHEM Ch 7
Terms
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(def)
the change of one or more substances into different substances - chemical reaction
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reactions that occur in liquids and form a gas - gas evolution
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a substance reacts with oxygen, emitting heat and forming one or more oxygen containing compounds; subcategory of oxidation-reduction reactions - combustion reactions
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electrons are transferred from one substance to another - oxidation-reduction reaction
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form solid substances in water - precipitation reactions
- in some cases, chemical reactions are not...
- noticeable to the naked eye
- evidences of a chemical reaction:
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1. color changes
2. formation of a solid or gas
3. heat absorption
4. light emission
-but are not always definitive evidence - these only conclusively prove that a chemical reaction has occurred:
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1. chemical analysis
2. changes at the atomic and molecular levels - chemical equations represent:
- chemical reactions
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the number of each type of atom on both sides of the equation is equal - balanced equation
- matter must be...
- conserved
- balanced equations change...
- the number of molecules but not the kinds of molecules
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a homogeneous mixture of a substance with water - aqueous solution
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substances that completely dissociates into ions in solutions - strong electrolytes
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resultant solutions - strong electrolyte solution
- not ionic compounds dissolve in...
- water
- a compound is soluble in a particular liquid if...
- it dissolves in that liquid
- a compound is insoluble if...
- it does not dissolve in the liquid
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form a solid or precipitate upon mixing 2 aqueous solutions - precipitation reaction
- precipitation reactions do not always occur when mixing:
- 2 aqueous solutions
- the key to predicting precipitation reactions is to understand:
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1. that only insoluble compounds form precipitations
2. if the potentially insoluble products are both soluble, then no reaction occurs. if one or both are insoluble then a precipitation occurs. -
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an equation showing the complete neutral formulas for every compound in the reaction - molecular equation
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showing the reactants and products as they are actually present in the solution - complete ionic equations
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do not participate in the reactions - spectator ions
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show only the species that actually participate in the reaction - net ionic equations
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reactions that form water upon mixin of an acid and a base - acid-base reactions
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reactions that evolve a gas - gas evolution reactions
- both reactions occur when...
- the cation of one reactant combines with the anion of another
- an acid is a compound characterized by:
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1. its sour taste
2. ability to dissolve some metals
3. its tendency to form H+ ions in solutions - a base is a compound characterized by:
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1. its bitter taste
2. slippery feel
3. tendency to form OH- ions in a solution - when an acid and base are mixed...
- the H+ from the acid combines with the OH- from the base to form H2O
- acid base reactions are also called:
- neutralization reactions
- water and ionic compound:
- salt
- acid + base -->
- water + salt
- some gas evolution reactions form:
- a gaseous product directly when the cation of one reactant reacts with the anion of the other
- other gas evolution reactions form:
- an intermediate product that then decomposes into a gas
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loss of electrons - oxidation
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gain of electrons - reduction
- oxidation and reduction both need to:
- occur together
- redox reactions are those in which:
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1. a substance reacts with elemental oxygen
2. a metal reacts with a nonmetal
3. more generally, one substance transfers electrons to another substance -
(def)
a type of redox reaction - combustion
- most of our society is derived from:
- combustion
- characterized by the reactions of a subtance with O2 to form one or more oxygen containing compounds
- combustion
- a way to classify chemical reactions is by:
- what atoms or groups of atoms do during the reaction
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(classifying chemical reactions)
sunthesis or combo - A + B -> AB
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(classifying chemical reactions)
decomposition - AB -> A + B
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(classifying chemical reactions)
displacement - A + BC -> AC + B
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(classifying chemical reactions)
double-displacement - AB + CD -> AD + CB
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simpler substances combine to form more complex substances
-simpler substances may be elements or compounds - synthesis or combination reactions
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a complex substance decomposes to form simpler substances
-substances may be elements or compounds - decomposition reactions
- require nergy in the form of heat, electrical current or light to make them happen
- decomposition reactions
- single displacement reaction; one element displaces another in a compound
- displacement reaction
- 2 elements or groups of elements in 2 different compounds exchange places to form 2 new compounds
- double-displacement reactions