GENCHEM MIDTERM 2

specific concentration

quantity of SOLUTE dissolved in a given quantity of solution (or solvent)

aqueous solution

solutions of solute in water (solvent)

concentration

• intensive property

• measured by molarity (M)

  • moles of solute per liter of solution

dilution

A concentrated solution is converted to dilute solution by adding solvent

solubility

the amount of substance that can be dissolved in a given quantity of solvent at a specified temperature

• insoluble (less than 0.01 mol/L)

polarity

• created in water molecule through its uneven distribution of electron charge and bent m/c shape

electrical conductivity

flow of electric current

• increases when ionic compounds dissolve

electrolytes

substances whose aqueous solutions conduct electricity (most contain ions)

• strong: soluble compounds that completely ionize in water

• weak: m/c compounds for which only a small fraction of m/c are ionized in water

nonelectrolytes

substances whose aqueous solutions do not conduct electricity (contains negligible amount of ions)

• most molecular compounds

precipitation reaction

2 soluble ionic compounds react to form an insoluble product (precipitate)

• key event: formation of an insoluble product through net removal of ions (m/c eq => net ionic eq)

molecular equation

shows all reactants and products as if they were intact, undissociated compounds

total ionic equation

shows all the soluble ionic substances as they actually exist (dissociated ions)

net ionic equation

spectator ions are excluded and only shows the chemical change

metathesis reaction

double displacement reaction

• ex) precipitation and acid-base

acids

Arrhenius: substances that in aqueous solutions produce hydrogen ions (H+)

For now: m/c substances that IONIZE in aqueous solutions, releasing hydrogen ions (H+ = proton)

• PROTON DONORS

strong acids

acids that ionize completely in an aqueous solutions (→)

H₂SO₄, HI, HBr, HNO₃, HCl, HClO₄

_{(SO I Brought NO Clean ClOthes)}

weak acids

acids for which only a small fraction of m/c are ionized (⇌)

HF, H₃PO₄, CH₃COOH

polyprotic acid

ionization is represented in stages

base

Arrhen: substances that produce OH- ions when dissolved in water

• proton acceptors

strong base

completely dissociates into ions in an aq solution

• group 1 hydroxides

• Sr Cat Bad (Sr, Ca, Ba)

weak bases

partially ionize in aqueous solution

• ammonia (NH₃)

titration

known concentration of one solution is used to determine the unknown concentration of another

standard solution

concentration is known

equivalence point

amount of H+ ions in the original volume of acid has reacted with SAME amount of OH- ions from buret

• moles of H+ and OH- are stoichiometrically equal

end point

point at which indicator changes colour (tiny excess of OH- ions changes colour)

• in calculations this excess is insignificant

oxidation reduction reactions

net movement of e- from one reactant (with less attractions for e-) to the reactant with MORE attraction for e-

• Ionic compounds TRANSFER e-

• Covalent compounds SHIFT e-

oxidation

loss of electrons

• reducing agent is oxidized (loses electrons)

reduction

gain of electrons

• oxidizing agent is reduced (gains electrons)

types of redox reactions

• combination (X+Y→Z)

• decomposition (Z→X+Y)

• single displacement (X+YZ→XZ+Y)

• combustion

activity series of metals

metals are ranked by their ability to displace H₂

• any metal can displace (reduce) the ions of metals BELOW it

  • single displacement won’t occur if metal is trying to displace ions of metal below it

pressure

force of collisions with walls

• force exerted per unit of surface area (F/A)

barometer

measures atmospheric pressure

• tube filled with Hg is inverted into a dish and vacuum forms above Hg

• P_Hg = P_atm

closed end manometer

Hg filled curved tube closed on one end and attached to flask at the other

• ∆h = P_gas

open end manometer

Hg filled curved tube is open at one end and attached to a flask at the other

• ∆h = difference between P_gas and P_atm

ideal gas

gas that exhibits linear relationships among volume, pressure, temperature, and amount

• described by gas laws

Boyles law

V∝1/P at constant temperature

• P₁V₁=P₂V₂

Charles law

V∝T at constant pressure

V₁/T₁ = V₂/T₂

avogadros law

V∝n at fixed pressure and temperature

V₁/n₁ = V₂/n₂

STP conditions

1 atm and 273.15K

Kinetic molecular theory

• negligible volume of particles compared to whole sample (point mass)

• negligible force

• elastic collisions

• Average KE of particles is proportional to absolute

maxwell boltzman distribution

most probable speed increases with temperature

temperature

a measure of the average KE of a particle

root mean square speed

a particle moving at this speed has average KE

real gases

• gas particles are NOT point mass with 0 volume

• Attractive and repulsive forces DO exist

strong acid and strong base

Net ionic: H⁺+ OH^- → H₂O

weak acid and strong base

intact acid m/c on reactant side for net ionic

• cation of strong base is spectator

ex) CH₃COOH + OH^- → H₂O + CH₃COO^-

insoluble base and strong acid

Intact base on reactant side for net ionic

ex) net: Mg(OH)₂ + 2H⁺ → 2H₂O + Mg²⁺