Lab Exam Chem 220

What is the formula for sodium hypochlorite?

NaClO

A “phase-transfer catalyst” is used in this reaction. Which of the substances below is that catalyst?

T-butylammonium hydrogen sulfate

The oxidation of a secondary alcohol with Clorox gives a product which is a member of which functional group?

ketone

When a primary alcohol is oxidized using a string oxidizing agent like K2Cr2O7 or KMnO4, what functional group does the product belong to?

carboxylic acid

H2 + I2 = 2HI, what direction will equilibirum shift is H2 gas is added?

right

H2 + I2 = 2HI, what direction will equilibirum shift if HI is removed as soon as formed?

right

Why was the reaction of dehydration of cyclohexanol was carried out with fractional distillation set up?

because of Le Chanciellers principle. This allows us to control which way the equillibrium goes and get more product

the dehydration of an alcohol requires the use of a catalyst to promote the loss of water. what is the compound used in this reaction as a catalyst?

phosphoric acid

the product of dehydration in this experiment is cyclohexene. To what functional group family does it belong?

alkene

The appartus used in this experiment is identical to that used in a previous experiment. What was it?

fractional distillation

what technique is used in this experiment to confirm that the conversion of cyclohexanol to cyclohexene has been achieved?

infrared spectroscopyw

which factor does not favor an SN2 reaction? ( strong nucleophile, polar aprotic solvent, tertiary substrate, methyl halide)

tertiary substrate

which of the following is not a nucleophile? ( NH3, CN-, CH3O-, NO2+)

NO2+

Consider a reaction in Q2 ( HO- + H3C-Br). What effect on the rate would result from simultaneously doubling the concentration of both methyl bromide and OH- ion?

it would increase the rate four times

What makes solvents suitable for recrystallization? 2 criteria

1) needs to be insouluable in cold solution, but soluable in hot solution

2) the solvent should not chemically react w compound thats being purified

What is the molecular formula for ethanol?

C2H6O

What is a hazard associated with ethanol?

its heavily flammanle and an intoxicant

what is the purpose of adding DI water after gravity filtration?

it adusts the saturation until correct level is reached, this helps turbidity and recrystallization formation

What is turbidity?

whne teh solution turns cloudy because of crystals forming and seperating from the suction

What is oiling out effect?

when oil forms instead of crystals when a mixture cools too rapidly

How can oiling out effect be avoided?

it cna be avodie dby cooling the solution slower and adjustig the water-ethanol solution

In a recrystallization lab, if the crystals failed to form after you cooled teh solution for a long time what should you do?

scratch the inside of the flask with a glass rod to encourage crystal formatin. If that doens’t work, attempt seeding

Why is a short stemmed funnel used?

when cooling is minimized to avoid early crystalization. this filters out the solid impurities fro the solution

Why is a buchner funnel used?

provide an air tight seal while suctioning occurs

What is an extraction?

its a seperation process that selectivelly transfers a component of ixture into different phase of matter

What is an everyday life example of an extraction?

coffee. Using the hot water to extract the coffe from the grounds is turning it from solid to liquid, extracting the drink

How do you know a solvent pair is miscible?

the pair will mix togetehr into a homogenous mixture with no sort of seperation. the pair has similar polarity and intermolecular forces

How do you know if a solvent pair is immiscible?

the pair will not mix togethr uniformly and will cause seperation in a layer. the pair does not have similar polarity or intermolecuar forces

How do you know if a solvent pair can be used for extraction?

the solvent pair needs to be immiscible

What are the hazards associated with diethyl ether?

it is highly flammable, it is also an anathestic and can knock people out and cause dizziness. it also readily forms peroxides

Def of boiling point

teh temp at which vapor pressure equals atmospheric pressure

how does boiling point of water change at higher altitude?

it decreases becasue the atmospheric pressure decreases which is what the vaopr pressure needs to equate in order for it to boil

What three intermolecular forces keep molecules together in the solid and liquid phase?

Van de Waal, dipole dipole and hydrogen bonds

why is it neccesary to add boiliing chips before starting distillation?

if you add them after starting, it can cause VIOLENT boiling.

what happens if you dont add boiling chips?

if you dont add them, superheating can occur and liquid may boil unevenly and cause intermittent violent boiling

how is it possibel during a fractional distillation a student observed a flask was boiling but thermometer shows 20 degrees celcius?

occurs when boiling has begun but the vapors have yet to reach teh thermometer bulb

if the thermometer during distillation consistently shows lower readings than expected, what are possible causes?

the thermometer may be incorrectly placed. the bulb should be right below the condensor

if there is a plateau in a distillation graph, what does the indicate

this indicates that that is the boiling point of one of the liquids. additionally that it is likely pure.

chromatography refers to the method of separating a mixture into its components by distribution between two phases. What are the two phases?

a mobile phase and a stationary phasein

in a gas chromatogram of a mixture, hwat information cna you obtain by comparing the areas of the peaks?

the relative amount ( % comp) of the compounds in the mixture