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30 Cards in this Set

  • Front
  • Back

Gas chromatography

Useful for separating out mixtures of volatile compounds.

What is a chromatograph and how does it work?

Machine used in gas chromatography.



A sample is injected where it is vaporized and forced by a carrier gas through a long column. Different compounds take different amounts of time to travel through the column and are detected as they exit the column.

What is a chromatogram?

Graph of data from gas chromatograph which consists of peaks as a function of time. The location of the peak depends on its identity; the size of the peak depends on the compounds amount.

What is Gas Chromatography Mass Spectrometry (GCMS)?

Gas chromatography separates the different components of a mixture. Mass spectrometry identifies the different components using a database.

In which lab did we use gas chromatography?

Determination of Ethanol in Beverages

In which lab did we use gas chromatography mass spectrometry?

Supercritical liquid extraction of essential oils

What is spectroscopy?

Interaction of light with matter

What does an infrared spectrophotometer (FTIR) do and what lab did we use it for?

Confirms identities of separated components based off peaks and valleys and shows purity of separated compounds.



-Identification of ibuprofen and caffeine and their purities.

What is Atomic Absorption (AA) used for? What lab was it intended for?

It detects metals and elements in a sample and analyzes their concentrations.



It was used to measure the copper 2+ concentration in the Solubility–Product Constant of Copper(ll) Iodate lab.

How does an AA (Atomic Absorption) instrument work?

The metal is a atomized by the energy of a flame and then analyzed by a beam of light with specific wavelengths unique to the metal which absorbs some of the light, and this absorption is measured by the instrument. The amount of light absorbed is proportional to the concentration of the metal in the solution.



-different atoms absorb/emit different colors


-good for a particular element

What is UV-Viz spectrophotometry used for?What lab did we use it in?

To measure the concentration of [copper] in a saturated solution in the Solubility – Product Constant of Copper(ll) Iodate

How does UV-Vis spectrophotometry work?

A beam of light is fractured into different wavelengths by a prism. Absorption of the solution is measured as a function of wavelength. The concentration is related to its absorbance according to Beer's Law.

What is a pH meter used for?

To measure the pH of a solution.

What is Beer's Law?

A = e L c



Absorbance


Length of path in cm


Concentration

What is significant about the equivalence point in a titration?

When the moles of titrant equal the moles of analyte this determines the concentration of the unknown solution/acid/base.

What is a titrant in titration?

The known solution

What is the analyte in a titration?

The unknown solution.

What is titration?

A technique in which a titrant is added from a buret to a known quantity of analyte until the reaction is complete to determine concentration of an unknown solution/base/acid.

What does a titration curve show?

Volume of titrant (independent variable) versus pH of solution (dependent variable).

When does pH = PKa?

At the midpoint/half the equivalence point when the concentration of a base is equal to its conjugate acid.

What is the difference between precision and accuracy?

Precision is the closeness of two or more measurements to each other. Accuracy is the closeness of a measurement to the true/known value.

What is the unknown and known components in this image?

A weak acid (unknown/analyte) titrated with a strong base (known/titrant).

What is the dilution equation?

M1V1=M2V2

How to calculate percent yield

Use stoichiometry to obtain theoretical yield.

What is a calibration curve?

Also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration.



Ex - Absorbance(Y) vs concentration(X-known M)

How to calculate standard deviation

Back (Definition)

How to calculate relative standard deviation

(get regu standard deviation first)

How does infrared spectroscopy work?

Also called vibrational spectroscopy. Uses infrared light to measure vibration speed of bonds. It depends on bond strength of functional groups and atom mass. Stronger bonds have faster speed. Heavier mass have slower speeds.

What is similar and different about UV-Vis and Infrared spectroscopy?

UV-Vis spectroscopy uses electron excitation.



Infrared uses vibrational spectroscopy to identify types of bonds of functional groups.



Both use light (but different types) to do this.

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