chapter 6 Flashcards
Chemical change
is any change that results in the formation of new chemicalsubstances.
At the molecular level, chemical change involves making or breaking of bonds between atoms.
Ex:
iron rusting (iron oxide forms) gasoline burning (water vapor and carbon dioxide form)
reactant
a substance or molecule that participates in a chemical reaction
product
a substance that forms in a chemical reaction.
The total energy before a reaction is equal to the total energy of the products and their surroundings,
i.e. energy is conserved in chemical reactions.
reactions that release energy (release of heat) are
exothermic.
reactions that absorb energy are
endothermic.
Synthesis Reaction
a reaction in which two or more substances combine to form a new compound: A +B —> AB,
ex: 2Na + Cl2 —> 2NaCl
Decomposition Reaction
a reaction in which a single compound breaks down to form two or more simpler substances: AB —> A + B.
Ex. 2H2O —> 2H2 + O2.
Electrolysis
is a technique that uses a _direct electri_c current (DC) to drive an otherwise non-spontaneous chemical reaction, such as decomposition of water.
Combustion reaction
the oxidation reaction of an organic compound, in which heat is released. Can there be a non-oxygen oxidation? yes, a redux reaction.
Reversible reactions ________.
are where the products can react to remake the original reactants.
If the forward reaction is exothermic, the reverse reaction is endothermic.
if O2 is a reactant, energy is released;
if O2 is a product energy is required. Makes sense.
Photosynthesis (endothermic) uses sun energy to O2 (oxidant) and C6H12O6 (combustible stuff).
Exothermic
Exothermic reactions transfer energy to the surroundings.
2CH4 + 4O2 —> 2CO2 + 4H2O + heat .
Single Displacement reaction
a reaction in which one element or radical takes the place of another element or radical in a compound.
Generally a more reactive element will take the place of a less reactive element.
AX + B —> BX + A
ex. 3CuCl2 + 2Al —> 2AlCl3 +3Cu
Double-Displacement Reaction
a reaction in which a gas, solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds.
AX + BY —> AY + BX,
ex Pb(NO3)2 + K2CrO4 —> PbCrO4 + 2KNO3.
Oxidation-Reduction reaction
aka
Redox reaction
any chemical change in which one species is oxidized (loses electrons), and another species is reduced (gains electrons);
Radical
a radical is an atom, molecule, or ion that has unpaired valence electrons, i.e electrons available for bonding.
Lewis structure shown:
a hydroxyl radical contains one unpaired electron
Substances that accept electrons are said to be _______.
reduced.
substances that give up electrons are said to be_______
oxidized.
Mole Ratio
the relative number of moles of the substance required to produce a given amount of product in a chemical reaction.
Defined as the ratio of moles of one substance to the moles of another substance in a balanced equation.
Reactions go faster at higher temperatures
The Kinetic Theory states that particles move faster at higher temperatures. The faster moving particles collide more often, and there are more opportunities for the particles to react.
Reactions go faster at higher pressures
gas particles have less space, so they have more collisions.
Chemical Equilibrium
the rate of a forward reaction is equal to the rate of the reverse reaction, i.e. the rates balance, and the concentrations of products and reactants remain unchanged.
For equilibrium to be reached, none of the reactants or products can escape, or enter.
Systems in equilibrium respond to minimize change.
If there is a change in the amount of reactants, a new equilibrium will be established.
La Chatlier’s Principle
if a change is made to a system in chemical equilibrium, the equilibrium shifts to pose the change until a new equilibrium is reached.
Endothermic
Endothermic reactions take in energy from the surroundings.
So I would have to “cook” (add heat to) the reactants:
2CO2 + 4H2O + HEAT —> 2CH4 + 4O2
nonspontaneous reaction
or
an unfavorable reaction
an endergonic reaction (also called a nonspontaneous reaction or an unfavorable reaction) is a chemical reaction in which the standard change in free energy is positive, and energy is absorbed.
Endergonic processes can be pushed or pulled by coupling them to highly exergonic reactions.
