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41 Cards in this Set
- Front
- Back
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A physical change
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alters the physical state of a substance without changing its composition
Ice to water |
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A chemical change-chemical reaction
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convert on substance to another
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Chemical reaction involve breaking bonds in the starting materials
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called reactants and forming new bonds in the products
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A chemical equation
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is an expression that uses chemical formulas and other symbols to illustrate what reactants constitute the starting materials in a reaction and what products are formed
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Chemical equations are written with
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reactants on the left and products on the right seperated by a reaction arrow
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Coefficients
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Coefficients show the number of molecules of a given element or compound that react or are formed
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Law of conservation of mass
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Atoms cannot be created or destroyed in a chemical reaction
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Multiply its coefficient by the subscript
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2O2 = 4 O atoms
2H2O = 4 H atoms + 2 O atoms |
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Coefficients are used to
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balance an equation
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Arrow
triangle (s) (l) (g) (aq) |
reaction arrow
heat solid liquid gas aqueous solution |
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Balanced chemical equation
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number of atoms of each element is equal on both sides of the equation
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Molar mass
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is the mass of one mole of any substance, reported in grams per mole
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atomic weight
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is the average mass of an element
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the Formula weight
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is the sum of the atomic weights of all the atoms in a compound reported in atomic mass units
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"Molecular weight"
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is often used in place of formula weight for covalent compounds
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The value of the molar mass of a compound in grams
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equals the value of its formula weight in amu
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Molar mass is very useful quantity because
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it relates the number of moles to the number of grams of a substance
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A balanced chemical equation
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also tells us the number of moles of each reactant that combine and the number of moles of each product formed
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Coefficients are used to form mole ratios,
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which can serve as conversion factors
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Use the mole ratio from the coefficients in the balanced equation
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to convert the number of moles of one compound (A) into the number of moles of another compound (B)
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Coefficients in chemical equations
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tell us the ratio of the number of molecules or moles that are involved in a chemical reaction
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The Theoretical yield is the amount of product
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expected from a given amount of reactant based on the coefficients in the balanced chemical equation
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Less then the maximum amount predicted
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is formed usually because of undesired reactions called Side reaction
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The actual yield
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is the amount of product isolated from a reaction
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Percent yield
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actual yield (g)/theoretical yield (g) x 100 = percent yield
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to determine the overall percent yield in a synthesis that has more then one step,
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multiply the percent yeild for each step
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Oxidation is the
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loss of electrons from an atom
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Reduction is the
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gain of electrons by an atom
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a redox reaction
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involves the transfer of electrons from one element to another
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A compound that gains electrons
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(is reduced) while causing another compound to be oxidized is called an oxidizing agent
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to determine the overall percent yield in a synthesis that has more then one step,
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multiply the percent yeild for each step
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Oxidation is the
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loss of electrons from an atom
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Reduction is the
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gain of electrons by an atom
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a redox reaction or Oxidation-reduction
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involves the transfer of electrons from one element to another
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A compound that gains electrons
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(is reduced) while causing another compound to be oxidized is called an oxidizing agent
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a compound that loses electrons
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(is oxidized) while causing another compound to be reduced is called the reducing agent
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When considering neutral atoms
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metal lose electrons and non metals gain electrons metals are reducing agents and nonmetals are oxidizing agent
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When considering ions,
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cations tend to gain electrons and anions tend to lose electrons-----Cations are reducing agents-----anions are oxidizing agents
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Oxidation Reactions
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Na-------Na+ + e-
Mg ------Mg 2+ + 2e- 2Cl- ------- Cl2 + 2e- 2O2- ----- O2 + 4 e- Electrons lost |
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Reduction Reactions
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Cl2 +2 e- --------- 2Cl -
O2 + 4 e- ------- 2 O 2- Cu2- + 2 e- ------ Cu Ag + + e- ------- Ag Electrons are gained |
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Iron rusts Fe2 O3
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this reaction Fe3+ is oxidized
and O2 is reduced to O2- |
