gen chem

When making ice cream, where is heat transferred from and where is it transferred to?

from ice cream mixture to ice and rock salt

What colligative property is displayed by making ice cream?

freezing point depression

Why is salt added to ice when trying to facilitate freezing point depression?

because the solution freezes at a lower temperature than water

T/F: Colligative properties depend only on the number and not the identity of the solute particles in a solution.

True

freezing point

the temp at which the solvent in solution and the pure solid solvent have the same vapor pressure (basically, solid and liquid are coexisting)

What causes freezing point depression (why are lower temps needed to freeze something)?

solute particles interfere ("stand between") the solvent particles, weakening the intermolecular forces and therefore lowering the freezing point

molality equation

m = moles solute / kg solvent

solute

material dissolved in something

solvent

material dissolving something

freezing point depression equation

∆t_f = t_f solution

K_f value for water

equation relating freezing point and van't Hoff factor

∆t_f = iK_fm

In the freezing point depression experiment, what temperature is the ice/salt bath supposed to be at?

In the freezing point depression experiment, what was the solute? Solvent?

solute: isopropyl alcohol; solvent: water

percent error equation

| (experimental

difference b/t molarity and molality

molarity: mols solute/ L solution; molality: mols solute/ kg solvent

As van't Hoff factor increases, does freezing point increase or decrease?

decrease

If the calculated molar mass of a compound is 10, but the actual molar mass is 5, what should the van't Hoff factor be?

1/2

What does the green dye react with that causes its color to change? What color does it change to? Is this the result of a structural change?

aromatic compound

contains plantar ring systems with alternating double bonds; ex: dyes

chromophore

the part of the molecule responsible for its color

As more methlyl groups are added, what happens to the color of a dye?

it changes (from red to reddish purple to blue to green)

does methyl green have resonance structures? does it act as a Lewis acid or a Lewis base?

The color of methyl green fades under ____ (acidic/basic) conditions. The reaction is ______(faster/slower) as conditions continue in this fashion (as the dye fades).

basic; faster

net reaction involving Na2HPO4 and Na3PO4 buffer system (experiment 2

rate of decolorization)

What order is the reaction involving Na2HPO4 and Na3PO4 buffer system? (experiment 2

rate of decolorization)

what is the observed rate law for the reaction involving Na2HPO4 and Na3PO4 buffer system? (experiment 2

rate of decolorization)

When a reaction is first order, but [h2O]>>[dye] , what will happen? What will the observed rate constant be in this case?

the reaction will be pseudo first order; k (obs) = k1[H2O] + k2[OH

Beer

Lambert Law

define each variable in the Beer

Lambert Law

equation relating the absorbance to the rate constant (k _obs)

when plotting

ln(A) v time, what is the slope equal to?

biological application of methyl green

staining DNA

Lewis acid

a compound or ionic species that can accept an electron pair from a donor compound

Lewis base

a compound or ionic species that can donate an electron pair to an acceptor compound

How could you find the concentration of OH

for multiple trials in an experiment?

Why is the slope of K_obs vs. [OH

] equal to k2?

Describe an experiment that would examine the effect of increased ionic strength on the observed rate constant.

Adding another salt to the experiment would increase ionic strength, but decrease the observed rate constant.

the molar concentration of a reactant will ______(increase/ decrease) over time and the molar concentration of product will _____ (increase/ decrease).

decrease; increase

catalysis

the increase int eh rate of a chemical reaction due to the participation of a substance called a catalyst

catalyst

lowers the activation energy of a reaction; allows reaction to proceed at a faster rate or under different conditions; is NOT consumed

What is the rate of a reaction dependent on?

the concentration of the reactants (and the catalyst, if there is one)

what is the overall rate law for a reaction?

a sum of all exponents

Can exponents representing the order of each reactant be determined by the written equation without experiments?

no

Arrhenius equation

k = Ae^ (

define the variables in the Arrhenius Equation

k= rate constant; A = frequency factor; e = e (on calculator); Ea = activation energy; R = 8.314 J/Kmol; T = temp (K)

activation energy

the difference in energy between the reactants and the transition state

reaction between iron(III) ion and iodide

2 Fe ^3+ + 3I

rate equation for reaction between iron(III) ion and iodide (normal and in terms of triiodide ion)

normal: rate = k[Fe3+]^m [I

Since you cannot find the reaction rate of iron (III)

iodide reaction, what can you do to find it?

what unreacted ion will form a dark blue complex with starch?

triiodide ion

As long as thiosulfate is present, will triiodide react with starch? what color will the solution be?

no; colorless

In a graph of ln(rate) v ln(Fe^3), what is the slope equal to?

the order of the reaction with respect to Fe^3+

In a graph of ln(rate) v ln(I

), what is the slope equal to?

In a graph of ln(k) v 1/T, what is the slope equal to?

Does the value of k change as the reaction temperature changes?

yes

What is used to maintain an elevated temperature in the chemical kinetics lab? A low temperature?

a hot water bath; a cold water bath

equation to find initial rate in chemical kinetics lab

rate =

activated carbon (/charcoal)

form of carbon with a very high surface area due to pores

how do chemists synthetically make Fe3O4 (magnetite)?

by combining Fe^2+ and Fe^3+ salts under basic conditions

ferrofluid

consists of nanoscale ferromagnetic particles evenly dispersed in a carrier fluid

what is the equation for making a nanocomposite (ex. 4) by combining FeCl3, FeCl2, NH3, and H2O?

2FeCl3 + FeCl2 + 8NH3 + 4H2O

nanocomposite

a multiphase solid material where one of the phases (or components) has one, two, or three dimensions of less than 100 nm

what does MAC stand for?

magnetite

After the MAC absorbs the pollutant dye, what is used to clean the MAC (and as a result, takes on the color of the pollutant)?

ethanol

% by mass equation

(mass of single compound / total mass of all compounds in item) x 100%

How is the removal of nitrates by alum similar to the absorption of organic pollutants by activated carbon?

both can absorb the pollutants from substances & therefore purify the substance

applications of ferrofluids

applications for nanocomposites

During a dynamic equilibrium, the rate of the forward reaction is _______ (greater than, less than, equal to) the rate of the reverse reaction.

equal to

Law of Mass Action

Keq = [C]^c[D]^d / [A]^a[B]^b

reaction b/t Fe^3+ and SCN^

What color does the Fe^3+/SCN^

system form?

how would you find the concentration of iron in a solution containing both Fe^3+ and FeSCN^2+?

total [Fe^3+] = [Fe^3+] + [FeSCN^2+]

Given (A/[Fe^3+][SCN^

]) = (A([Fe^3+]+[SCN^

When finding the absorbance of KSCN + Fe(NO3)3 solutions in ex., what compound is used as the reference?

HNO3

How do you calculate the concentration of an ion in a solution given the molarity and the volumes of the total solution and the ion's solution?

M x (volume solution with ion/ total volume of solution)

neutralization reaction

a chemical reaction between an acid and a base to form a salt and water

acid

proton donor

base

proton acceptor

strong acid

ionizes almost completely in aqueous solution

the larger the Ks, the ______ (stronger/ weaker) the acid.

stronger

what technique is used to determine the extent of ionization and Ka for a weak acid?

pH titration

equivalence point

the point of the titration where a stoichiometric amount of base has been added; just enough base has been added to completely react with all of the acid present

at the equivalence point, what ion is dominantly present? HA or A

? At the start of the titration? At the halfway point?

the equivalency point for a titration between a weak acid and a strong base will occur at a pH ____ (above/ below/at) 7.

above

concentration of HA equation

Ma = MbVb/Va

% ionization equation

[H3O+]/Ma x100%

Henderson

Hasselbalch equation

at the halfway point, what is the relationship between pH and pKa?

pH= pKa; (and therefore [H3O+] = Ka)

How to clean an electrode before transferring to another solution

rinse with diH2O and dry with a soft tissue

what does the pH do as the equivalency point is approached?

it changes drastically

Ka at the eq point equation (in terms of A

, HA, and H3O+)

relationship b/t pKa and KA

pKa =

concentration (m/V) as a percent process/equation

mol/L x g/mol x L/mL x 100%

how to find K' values given Ka or Kb

K' = Ka (or Kb)/Kw

solubility product constants

describe saturated solutions of ionic compounds with relatively low solubilities

What does the common ion effect do?

decreases the solubility

process to determine Ksp of Ba(NO3)2

Ba(NO3)2 + H2O

Ksp equation for Ba(NO3)2 + H2O

Ksp = [Ba^2+][NO3^