ThermoChem/Kinetics/LiquidsSolidsGases

thermochemistry

the relationship between chemistry and energy

• how chemical reactions can exchange energy with their surroundings

energy

the ability to do work or cause change

work

the result of a force acting on a distance

• gases do work (can expand or compress)

heat

a process quantity

• process by which energy is transferred across the boundary of a system due to a difference in temperature between the two sides of the boundary

surroundings

everything outside the system that can exchange energy and/or matter with the system

• essentially, if you have a chemical reaction going on, the surroundings is the solution.

State Functions

properties of a system for which the value does not depend on the path taken to reach that value.

• final and initial are considered.

• ALL capitals

Path functions

A property of a system that does depend on what path is taken to reach a specific value. Multiple steps results in a different value.

Endothermic Reaction

system absorbs more heat than it loses

• heat energy from the surroundings is changed to PE of the System

• temp of surroundings decreases

Exothermic Reaction

system releases heat but does not lose temperature

• PE is converted to heat energy

• the surroundings increase in temperature as the system releases this heat

heat enthalpy (delta H)

used to quantify the transfer of heat in or out of the system

Zeroth Law

Two systems at different temperatures will eventually come into thermal equilibrium as heat is transferred.

Time-Temperature Graph Problem

The graph starts with a solid, increase in temp, then flat line, which means equilibrium between solid and liquid.

Specific Heat needed to find joules for temperature at each temp increase. SH changes for each state of matter. you need molar heat of fusion and molar heat of vaporization.

Kinetics

what occurs during a chemical reaction

• speed or rate of a reaction

speed of a chemical process depends on several factors

concentration of reactions

nature of reactants

temperature

the influence of catalysts

surface area of reactants

rate of reaction

change in concentration / change in time

• reactants are written in such a way that the decrease is emphasized

• products are written in such a way that the increase is emphasized

• always final - initial conditions

• concentration/time [concentration] [HCl} symbolizes molarity

rate of disappearance

-[]/delta T. Rate of disappearance is always negative because it is for reactants that are consumed. the negative makes the expression positive

rate of appearance

this is for products, no negative sign

rate relationships in a reaction

4NH3 + 5O2 yields 4NO + 6H2O

• this written in rate relationships is (1/4)(NH3 Rate) = (1/5)(O2 rate) = (1/4)(NO rate) = (1/6)(H2O rate)