CHEM 120L Lab Exam

describe the reaction series from copper wire to copper metal

Cu --> Cu(NO3)2 --> Cu(OH)2 --> CuO --> Cu(SO4)2 -- 5H2O --> Cu

what is added to copper to make copper nitrate?

nitric acid, HNO3

what is added to copper nitrate to make copper hydroxide?

NaOH, sodium hydroxide

what is added to copper hydroxide to make copper oxide?

heated, solid is removed

what is added to copper oxide to make copper sulphate?

sulphuric acid, H2SO4

what is added to copper sulphate to make pure copper?

zinc metal

how is excess zinc removed from the copper metal?

HCl

define filtrate

liquid that has passed through a filter

define decant

carefully pour off liquid

Define supernatant

the clear liquid that remains at the top after a precipitate settles

define bumping

when a liquid superheats and flies out of the flask

distiguish between the three types of fires

A: paper, wood, plastic

B: gasoline, solvents, grease

C: electrical fires

how should you combine acid and water?

pour acid into water

how should one carry glass tubing?

vertically

how should thermometers be placed?

at right angles

how is boiling point and impurities related?

obviously, if the boiling point is anything other than normal then it is incorrect. however, higher boiling points contain more impurities because it is harder to break down.

explain the overall equation to synthesize acetaminophen

p-aminophenol + acetic anhydride --> acetaminophen + acetic acid

what are the steps to acetaminophen synthesis?

dissovle + combine two reactants

cool in ice water bath

recover product in vaccum filtration

dissolve product

cool in ice water bath

use vaccuum filtration

differentiate amines from amides

amides have oxygen

explain the difference between a primary and secondary standard

a primary standard has a known concentration. a secondary standard is determined relative to it.

how do you find molar mass, given that an acid is diprotic and standard titration knowledge?

find mols of known (NaOH)

divide by two to get the mols of acid

find the concentration of the acid by dividing the mols by the volume of solution needed to reach the endpoint. This is the concentration of the acid

multiply the concentration by the volume of the flask to get mols

divide the mass of the acid by the mols to get the molar mass

describe the characteristics of a strong acid strong base titration

each is fully ionized in aqueous solution and can be written as ions

describe the characteristics of a weak acid strong base titration

as the weak acid reacts, it produces hydronium ions in water, which react strongly with the base

how is the end point indicated?

rapid rise in pH is picked up by indicator

how to convert ppm to mol/L

convert to g (divide by 1000) and divide by molar mass

what is quantitative transfer?

involves no loss of sample, can be liquid or solid

what is a stationary phase?

solid, gel, immobalized liquid in the bed (negatively charged resin)

what is a chromatography bed?

where it 'lies', the glass that holds the resin up (glass column)

what is a mobile phase?

the solvent that carries liquid through the stationary phase (DI water)

what is the a delivery system?

the force that pushes the mobile phase through the stationary phase (gravity)

what is a detector?

quantifying the substances as they leave the stationary phase (titration)

eluate vs eluent vs elute

leaving the column vs loaded into the column vs seperation process

how many significant digits does an analytical balance have?

5

to convert angstrom to wavenumber

multiply by 1e-8

divide the answer by 1

spectra of fluorescent vs incandescent lamps

fluorescent is individual lines whereas incandescent is a spectrum, because incandescent includes varying parts of all frequencies in the visible spectrum

who is the visible light series named after

Balmer

who is the ultraviolet light series named after

Lyman

who is the infared light series named after

Paschen

what transitions can be seen in the lab?

anything that falls to 2. Anything that falls higher or lower than 2 cannot be seen

must also start lower than 7

Following an equation, you are given the concentration of copper. What is the mass of Na2S (in the same ratio) that must be added to 10L of solution to precpitate copper?

multiply concentration by volume

multiply by molar mass

what is organic synthesis?

The preparation of complex organic molecules from simple starting materials (involved carbon)

what is the purification step?

melting and allowing the acetaminophen to recrystalize

What is the primary standard used in the Identification of an Unknown Solid Acid experiment?

oxalic acid dihydrate

how do you know when to divide/multiply by the type of acid?

divide: concentration/information about the acid

multiply: concentration/information about NaOH or the base

Using the approximate concentration of the NaOH titrant and the range of sample concentrations given in your manual, which of the following is the best estimate for the volume of titrant used to titrate one sample:

10 - 30 mL

what should be done to make the fire of a bunsen burner hotter?

open the air at the barrel. bigger = gas

Which of the following would increase percent yield during the Reactions of Copper Experiment

not all zinc was removed

Failing to evaporate all water out of the evaporating dish in the final step

Overheating of metallic copper resulting in the formation of copper oxides

True or false: the more soluble a material is in solvent, the better it will recrystallize

false

Put the steps for weighing by difference in the correct order

weigh full beaker

transfer a third

transfer half

transfer all to clean and empty flask and reweigh

In cation exchange chromatography of an unknown, what assumptions must be made

No other cations are present in the solution

The solution must be neutral

Select all the correct advantages of weighing by difference

Only (n+1) weighings are needed

Balance is not zeroed between weighings

It does not matter if exactly the same amount is weighed into each flask (and it may be beneficial)

Which of the following statements are true regarding the reaction between p-aminophenol and acetic anhydride.

Acetic acid is formed as a by-product, by the reaction between the unused acetate ion of acetic anhydride and the hydrogen ion lost from the amine group of p-aminophenol.

As the reaction proceeds, p-aminophenol loses a hydrogen ion from its amine group.

As the reaction proceeds, an acetyl group binds to the nitrogen of p-aminophenol.

true or false: In the technique of analytical weighing by difference the receiving flasks used need to be clean, but do not need to be dry.

true

Calculate the mass of NaOH(s) that must be dissolved in exactly 1L of solution so that 32.00 mL of this solution is required to titrate to the equivalence point a solution containing 0.5453 g of a diprotic acid with a molar mass of 142.4 g/mol.

Molar mass of NaOH = 39.997 g/mol

explain the steps!

find the mols of acid by dividing the mass by the molar mass

find the concentration of the acid using the specified equivalence point

turn this into mols of NaOH by multiplying by the volume of NaOH provided (it's 1 so you don't have to do anything)

multiply by 2 because the acid is diprotic

multiply by the molar mass to get grams of NaOH

The indicator phenolphthalein is a weak organic acid whose protonated form is:

colourless