Chem 3 Exam

what does aqueous (aq) mean?

dissolved in water

What does △ mean in chemical equations?

input of heat

what do water soluble ionic compounds do in water?

dissociates into its ionic components

what do strong acids/strong bases do in water?

dissociate completely in water

How are molecular, full ionic, and net ionic equations different?

molecular: full equation with states of matter

full ionic: dissociates soluble compounds into their ions (only aq states)

net ionic: deletes spectator ions from full ionic (ones that appear on both sides)

combination

2 or more reactants combine to form a single product (A+B—>AB)

decomposition

2 or more products form a single reactant (AB—>A+B)

combustion

a substance burns in the presence of O₂ (contains C, H, O—> CO₂ + H₂O)

single displacement

one solid metal exchanges to produce a different solid, metal, hydrogen/halogen

double displacement(metathesis/exchange)

can be precipitation or molecular product

neutralization

acid + base —> salt + water

a neutralization reaction is classified under what other reaction?

double displacement

acid-base

H⁺ is transferred from one chemical species to another

redox

involves the change in oxidation # of 1 or more reactants via the transfer of electrons

condensation

2 molecules combine + H₂O is released

precipitation

dissolved substances react to form a solid (precipitate)

• the anions form 2 diff ionic compounds exchange cations

Solubility Rules: NH₄⁺

always soluble (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺)

Solubility Rules: halides

are soluble

• except (Cl^-, Br^-, I^-) containing Ag⁺, Hg₂²⁺, Pb²⁺

• except (F^-) containing group 2 metal cations, Pb²⁺, Fe³⁺

Solubility Rules: chlorates, bicarbonates, acetates, nitrates

always soluble (C₂H₃O₂^-, HCO₃^- , NO₃^- , ClO₃^-)

Solubility Rules: sulfates

soluble

• except compounds with Ag⁺, Ba²⁺, Ca²⁺, Hg₂²⁺, Pb²⁺, Sr²⁺

Solubility Rules: insoluble compounds

• CO₃^2-, CrO₄^2-, PO₃^4-, S^2- except with group 1 cations and NH₄⁺

• OH^- except compounds with group 1 cations and Ba²⁺

strong acid

reaction is 100% efficient (completely reacts w/water —> H⁺)

weak acid

partially reacts with water

Arrhenius acid

substance that produces H⁺/H₃O⁺ when dissolved

Arrhenius base

substance that produces OH^- when dissolved

bronsted-lowry acid/bases

bronsted-lowry acid: proton donor

bronsted-lowry base: proton acceptor

What are the strong acids?

HClO₄, HCl, HBr, HI, HNO₃, H₂SO₄

What are the strong bases?

LiOH, NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂

What are the weak acids?

HF, H₃PO₄, CH₃COOH, H₂CO₃, HCN, HCOOH, C₆H₅COOH

What are the weak bases?

NH₃, CH₃NH₂

monoprotic acid

1 proton to donate

polyprotic acid

more than 1 acidic H atom

oxidation

loss of e^- (reducing agent)

reduction

gain of e^- (oxidizing agent)

oxidation #’s

the charge its atoms would possess if the compound was ionic

Oxidation # steps:

1. oxidation # of an atom in an elemental substance is zero

2. oxidation # of a monatomic ion = ion’s charge

3. oxidation # for common metals

   1. hydrogen: +1 when combined w/nonmetals/ -1 when combined w/metals

   2. oxygen: -2 for most (sometimes -1, peroxides O₂^2-)(rarely -1/2, superoxides O₂^-) + values when combined w/F

   3. halogens: -1 for F, -1 for others

      1. + when combined w/O₂ + halogens

4. sum of oxidation #’s for all atoms in a molecule/polyatomic ion = the charge of molecule/ion

stoichiometry

quantitive relationships in the reaction

How can stoichiometry problems be converted?

mass ←→ mol reactant ←→ mol product ←→ mass

Steps for stoichiometry:

1. write balanced equation

2. convert known substances to moles

3. use coefficients to calc the # of mols + back to quantities

limiting reactant

reactant used up 1st in reaction

excess reactant

those present in quantity greater than necessary to react w/the quantity of the limiting reactant

What is the percent yield?

(actual yield/theoretical yield) x 100

How to find limiting and excess reactants?

(mols of product) x (molar ratio) = smallest = LR

How to find excess reactant left over?

LR —> mols of ER

actual - used = excess reactant left over

2 common analytical techniques ___ + ___ allow for the quantitative determination of the amount/concentration of a substance

titration, gravimetric analysis

thermochemistry

the study of measuring the amount of heat (energy) absorbed/released during a chem reaction/physical change

energy

capacity to supply heat/do work

work

the process of moving an object against opposing forces (W)

kinetic energy

associated with the motion of an object

potential energy

associated with the position/composition of an object

chemical energy

associated with the relative positions of e^- and nuclei of atoms and molecules

Law of Conservation of Energy

energy can never be created/destroyed-can only be transferred from on object to another

system

a part of the universe that is of specific interest (substances involved in chem + phys changes)

surroundings

constitute the rest of the universe outside the system

universe =

system + surroundings

temperature

quantitative measure of ‘hot’/’cold’

when temp increases, substances ____

expand

heat

transfer of thermal energy between 2 bodies til thermal equilibrium

exothermic process

when heat is transferred from surroundings to the system (feels hot/releases energy)

endothermic process

when heat is transferred from system to the surroundings (feels cold/absorbs energy)

heat is the ___ of thermal energy

flow

temp is the ____ of thermal energy in a sample of matter

measure

an increase in temp = an increase in _____

thermal energy

heat capacity (C)

the amount of heat required to change its temp by 1 degree Celcius

is heat capacity (C) extensive or intensive ?

extensive-diff amounts of a substance

specific heat (c)

the amount of heat required to raise the temp of 1g of the substance by 1 degree Celcius

is specific heat extensive or intensive?

intensive-depends on kind of substance (type not amount)

What is water’s specific heat?

4.184 J/gxC

calorimetry

used to measure amounts of heat transferred to/from a substance

• heat is exchanged w/a calibrated object (calorimeter)

thermodynamics

general study of energy and its interconversions

1st law of thermodynamics

the total energy of the universe is constant (only transferred/transformed)

internal energy of a system =

the sum of the KE + PE of all particles that compose the system (state of function)

state function

something that depends only on the state of the system + not how it arrived at the time

energy absorbed = __ energy

postive

energy released = __ energy

negative

surroundings do work on the system = ___ work

postive

system does work on the surroundings = ___ work

negative

enthalpy

the sum of its internal energy (U) and the product of the system’s pressure + volume (PV)

what variables are state functions?

pressure, volume, PV, enthalpy

what variable is not a state function?

work

what happens when an enthalpy equation is reversed?

sign of enthalpy (▵H) changes (±)

Hess’s Law

if a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps