Chapter 5 and Thermochemistry Lab

Electrolytes

substances that dissolve in water and conduct electricity through ions in solution

Strong electrolytes

substances that completely dissociate into ions; good conductors

Strong electrolyte examples

strong acids/bases

Nonelectrolytes

substances that remain as uncharged species in solution (no ions) or stay in solid form (insoluble solid)

Nonelectrolyte examples

sugar, Ag(anion)

Weak Electrolytes

substances that only partially dissociate into ions; conducts electricity but not well

Weak Electrolyte examples

vinegar, weak acids/bases

strong acids

acids that completely ionize

Weak Acids

acids that do not completely ionize

Arrow in both directions ←→

reaction is going in both directions (reversible)

Acid Arrhenius defintion

molecular compounds that ionize to produce H⁺ ions when they dissolve in water

Base Arrhenius definition

compounds that ionize to produce OH^- ions when they dissolve in water

Acid Bronstead-Lowry Definition

proton donors

Base Bronstead-Lowry definition

proton acceptors

Hydronium ion (H₃O⁺)

produced when H⁺ in solution react with water

Monoprotic acids

acids that produce a single proton

Monoprotic acid examples

HCl, HBr, HI

Polyprotic acids

acids that produce multiple protons

Polyprotic acid examples

H₂SO₄, H₃PO₄

Often, monoprotic acids are _____ acids while polyprotic acids are ____ acids

strong; weak

Strong Acids

HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄, HClO₃

HCl

hydrochloric acid

HBr

hydrobromic acid

HI

hydroiodic acid

HNO₃

nitric acid

H₂SO₄

sulfuric acid

HClO₄

perchloric acid

HClO₃

chloric acid

Strong Bases

alkali or alkaline earth metals + OH

NaOH

sodium hydroxide

LiOH

lithium hydroxide

KOH

potassium hydroxide

Ca(OH)₂

calcium hydroxide

Ba(OH)₂

barium hydroxide

CsOH

cesium hydroxide

RbOH

rubidium hydroxide

Sr(OH)₂

strontium hydroxide

Strong acids and bases do what?

completely dissociate

Acid + Base →

water + salt

Net Ionic equation of strong acid + strong base

H⁺_(aq) + OH^-_(aq) → H₂O_(l)

Net ionic equation for weak acid + strong base

HA_(aq) + OH^-_(aq) → H₂O_(l) + A^-_(aq)

At equivalence point, moles of acid ____ moles of base

equals

Acid-base neutralization ____ heat

releases

Exothermic reactions

release heat as product

Endothermic reactions

absorb heat as reactant

Temperature

measure of the average kinetic energy of molecules in a system

Heat

q; measure of the transfer of (thermal) energy

heat equation (q)

q = m x C_s x (ΔT)

m in heat equation

mass (g)

q in heat equation

heat (in J)

C_s in heat equation

specific heat (J/g-C)

ΔT in heat equation

temp change (C)

How do you find J/mol from q in J?

divide by moles of product (A^-)

System

part of the universe focusing on

Surrounding

the rest of the universe

1st Law of Thermodynamics- Energy Conservation

total energy of the universe is constant- not created or destroyed

1st Law of Thermodynamics- Energy Conservation Equation

ΔE_universe = 0 = ΔE_system + ΔE_surroundings

ΔE_system = 

-ΔE_surroundings

Energy flows from

hotter substance to cold

q_system =

-q_surroundings

Mole Fraction

relative number of moles of one thing vs. total moles of

Mole Fraction equation

X_B = (moles of B) / (total moles) = (moles of base) / [(moles of acid) + (moles of base)]

When does a reaction produce the most product?

equivalence point

Apex of q vs. mole fraction of base graph

max amount of product formed and max amount of heat released; stoichiometric equivalence point

Differences in q vs. mole plots are because of

differences in structures of the compounds

How much heat is released per mole of H⁺ being released?

~ 50kJ