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Chemistry 027
Lab Practical I Prep
39
Chemistry
Undergraduate 1
07/08/2008

Additional Chemistry Flashcards

 


 

Cards

Term

 

 

What is the kinetic energy of an ejected electron equal to?

Definition

The difference between the photon energy and the ionization energy (binding energy).

Term

 

 

What does a gaseous atom do to start photoelectron spectroscopy?

Definition

Absorbs a high energy UV or X-ray photon of electromagnetic radiation.

Term

What does orbital ionization energy represent for an atom’s electrons?

 

 
Definition
 

The tightness of the attraction of an electron by the electrostatic attraction between positive protons in the nucleus and the negative charge of the electron.

Term

 

If ionization energy was very high, what could be inferred of the released electron?

 

 

Definition

 

 

That the electron was very tightly bound.

Term

 

 

Equation for ionization energy

 

 

Definition
Ionization energy = E(photon) – E (KE)
Term

 

 

Zero energy level

 

Definition

Hypothetically, if an electron was in a vacuum, then it’s energy level would be 0. This would be because there is no kinetic energy, and therefore no movement.

Term

What is an electrostatic analyzer?

 

Definition

 

 

A tool used to measure the kinetic energy of a photoelectron. This is done by measuring the speed of the electrons

Term

 

 

Why are the walls of an analyzer curved?

 

Definition

 

 

At the end of the “tunnel” there is a slit through which the electrons must move. Only electrons which move at a certain speed may pass through this aperture. Electrons which are too fast or too slow will collide with the walls of the curved analyzer and stick to the charged walls.

 
Term

 

 

Why do the charges on the plates at the end of the curved analyzer change slowly?

Definition

 

They are used to scan the photoelectric spectrum by changing the amount fo positive and negative charges ont eh plates of the analyzer. This gradated change brings differently charged electrons into focus.

Term

 

 

What is the photoelectron spectrum of a gaseous atom?

 

Definition

 

 

A set of peaks representing the energies of the orbitals.

Term

 

 

   Relationship between height of peak on graph and number of electrons.

 

 

 

Definition

 

Proportional.

Term

 

Common reasons why one ionization potential is higher than the other:

 

Definition

-A has more protons and than B, therefore, the binding energy is greater

- its shell is half filled/all filled, and thus has great stability and resists losing electrons

- electron repulsions on outer-shell electrons beat the repulsions on degenerate orbitals

Term

 

What do the wave functions include?

 

 

Definition

 

  -a series of numbers called quantum numbers which are used to identify the different orbitals as to their average distance from the nucleus.

Term

 

 

Effective nuclear charge

 

 

Definition

 

 

Z(eff) = Z (actual) – (electron repulsions)

Term

 

 

Why are the 4s orbitals normally chosen over the 3d orbitals in choosing electrons for the creation of ions?

 

 

Definition

 

 

     4s orbitals, although filled before the 3d orbitals, are nonetheless at a higher energy level, and the atom can’t wait to get rid of their electrons

Term

 

 

What is the active compound in aspirin?

 

Definition

Salicylic acid.

 
Term

 

What can be done to make salicylic acid less irritating to membranes?

 

 

Definition

 

Replacement of the acidic OH group with an acetyl group

Term

 

What group do esters contain?

Definition

Carboxyls.

O=<R and Or’

Term

 

Characteristics of an ester (o-hydroxybenzoic acid, in this case)

Definition

Acetylsalicylic acid : white, powdery like talc

Methyl salicylate : Pleasant smell

Term

 

What would be observed after placing a drop of 1% iron III chloride into a test tube containing salicylic acid?

Definition

 

The solution would turn hot pink or purple.

Term

 

Reactants of acetylsalicylic acid:

 

Definition

 

Salicylic acid + acetic anhydride è Aspirin + Acetic Acid

Normally, it is made from salicylic acid and acetic acid, but this lab uses a more reactive compound called acetic anhydride. (add an acetyl O=<H3C + O group)

Term

 

Reactants of methyl salicylate:

 

Definition

 

Salicylic acid + methanol, add CH2 to the right-hand OH, KEEP the hydroxyl group on top.

Term

 

Phenol

 

Definition

 

A class of compounds where OH is attached to a benzene ring. Present in salicylic acid and methyl salicylate, but not aspirin. This stuff can kill you. Colors: green/blue, red/purple in presence of 1% iron III ion

Term

 

Procedure for synthesis of aspirin (6 steps)

Definition

1) measure 2.8 to 3.2 g salicylic acid and transfer to 125 ml flask

2) add 6 ml acetic anhydride and five drops of sulfuric acid.

3) mix thoroughly and place flask in boiling water (80 degrees Celsius) for 20 minutes

4) place in an ice-water bath and add 40 ml of DI water and wait for crystals to form, breaking up any oil that collects at the top

5) filter the product. Use the air-filter tap on the sink. Press dry. Air dry crystals.

6) weigh and conduct the 1% iron III Cl test. Does it turn purple? If so, there is unreacted salicylic acid present.

Term

 

What is recrystallization?

 

Definition

 

Dissolving a substance in a suitable solvent at the solvent’s boiling point allowing them to recrystallize and leave impurities behind in the solution.

Term

 

What is characteristic of a good solvent?

Definition

 

High temp=high solubility, low temp=low solubility

Term

 

During recrystallization, how much ethanol is needed to dissolve the crude product?

 

Definition

 

10ml for every 3 grams. (cross-multiply)

Term

 

theoretical yield:

 

Definition

 

(grams salicylic acid used) x (1 mol salicylic acid)/(grams salicylic acid in 1 mol) = mols salicylic acid

mols salicylic acid = mols of expected product of aspirin

 
Term

actual yield:

 

Definition

crude product/ expected product

dry product / expected product

Term

phenol

 

Carboxylic acid group

 

Definition

OH

 

CO2H

Term

 

Hydrolysis reaction

Definition

 

Reaction where wet aspirin decomposes into a benzene ring with a carboxylic acid group and a phenol group attached, as well as a mol of acetic acid

Term

 

Indicator

 

 

Definition

 

Phenolphthalein

Term

 

Phenolphthalein in the presence of bases

 

 

Definition

 

Pink

Term

 

Purpose of back-titration

 

Definition

To determine the moles of pure aspirin by backtitrating the NaOH with HCl.

Term

 

The moles of hydroxide consumed are equal to…

Definition

 

… the mols of acetylsalicylic acid in the product

Term

 

What is the point of doing an initial titration?

Definition

 

To determine the total number of moles of acid species in the product

Term

 

Base-promoted hydrolysis

 

Definition

 

A reaction where heat is used to drive the decomposition of aspirin with NaOH

 
Term

 

 

What do we use the ethanol for?

 

Definition

 

To neutralize the acids in the solution

Term

 

Moles of hydroxide [OH-] equal ....

Definition

 

 

... moles of acetylsalicylic acid.

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