Chem Sem. 2 Final

reactants

The starting substances in a chemical reaction

products

The ending substances in a chemical reaction

stoichiometry

Quantitative relationships between the amounts of reactants used and the amount of reactants formed by a chemical reaction

mole ratio

Ratio between the numbers of moles of any two substances in a balanced chemical equation

limiting reactants/reagents

Limits the extent of a reaction, determines the amount of product formed

excess reactants/reagents

Reactants leftover when a reaction stops

theoretical yield

Maximum amount of products that can be produced from a given amount of reactants

actual yield

Amount of products produced when a chemical reaction is carried out in an experiment

percent yield

Ratio over actual/theoretical yield as a percent

law of conservation of mass/matter

Matter cannot be created or destroyed, only moved

energy

The ability to do work or produce heat

law of conservation of energy

Energy can be converted from one form to another but not created nor destroyed

chemical potential energy

Energy stored in a substance because of its composition

heat

Energy in the process of flowing from a warmer object to a cooler object

specific heat

Amount of heat required to raise the temperature of one gram of a specific substance by one degree Celsius

calorimeter

Insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process

thermochemistry

Study of heat changes that accompany chemical reactions and phase changes

system

The specific part of the universe that contains the reaction or process you wish to study

surroundings

Everything in the universe other than the system

universe

System plus its surroundings

enthalpy

Heat content of a system at constant pressure

Hess’s law

If you add two plus thermochemical equations to produce the final equation for a reaction, the sum of enthalpy changes for individual reactions is the enthalpy change for the final reaction

spontaneous process

Any physical or chemical change that once begun occurs with no outside intervention

entropy

(S) Measure of the number of possible ways energy in a system can be distributed; chaos

second law of thermodynamics

Spontaneous processes always proceed in a way that the entropy of the universe increases

free energy

Energy that is available to do work

endothermic reaction

Energy is absorbed in a reaction

exothermic reaction

Energy is released in a reaction

reaction rate

Change in concentration of a reactant or product per unit of time mol/Lxs

collision theory

Atoms, ions, and molecules must collide in order to react

activated complex

Temporary, unstable arrangement of atoms in which old bonds are breaking and new bonds are formed

activation energy

Minimum amount of energy that reacting particles must have to form an activated complex

catalyst

A substance that increases the rate of a chemical reaction without being consumed in a reaction

inhibitor

A substance that slows down or inhibits reaction rates

rate law

Relationship between the rate of a chemical equation and concentration of reactants

specific rate constant

K; Relates reaction rate and the concentrations of reactants at a given temperature

reaction order

How rate is affected by the concentration of that reactant

initial rates

R-Instantaneous rate at the start of a reaction

instantaneous rates

R-slope of the straight line tangent to the curve at a specific time

Factors affecting reaction rate

Temperature, surface area, concentration, catalysts/inhibitors

chemical equilibrium

Forward and reverse reactions balance each other as they take place at equal rates

common ion effect

lowering of solubility of a substance because of the presence of a common ion

common ion

Ion that is common to two or more ionic compounds