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Flashcards in Spectroscopy & synthesis Deck (17):

How can IR radiation be used to identify bonds?

Absorbtion of infrared radiation causes covalent bonds to vibrate. Each bond absorbs IR radiation at a characteristic frequency, so radiation can be used to identify specific bond types.


What is the fingerprint region on an IR spectrum?

The region of absorbance below 1500 cm^-1 that gives a collection of sporadic peaks that can be used to identify specific compounds like a fingerprint.


How the axis on an IR spectrum labelled?

Absorbance/% against wavenumber/cm^-1


Define the greenhouse effect.

The warming of the atmosphere due to the trapping of infrared radiation by absorption of molecular bonds.


What are the three most prevalent greenhouse gasses in the earth's atmosphere?

H2O, CO2 and CH4
Water, carbon dioxide and methane


How do greenhouse gasses trap heat?

Bonds in greenhouse gases absorb IR radiation and vibrate. They then release heat, either into space or back towards earth.


Which two factors determine a gas's contribution to the greenhouse effect?

Energy absorbed by bonds, and the abundance of absorbing molecules.


Give three consequences of global warming.

Rising sea levels, climate change, loss of drinking water


What is carbon capture and storage?

The process of trapping greenhouse gas emissions and storing them in dry oil wells using the same pipes used to extract oil.


How are the axis of a mass spectrum labelled?

Percentage abundance against mass per charge (m/z)


What does m/z tell us?

The relative mass of an isotope


How are samples ionised for mass spectrometry?

Electrons are fired at samples in order to knock off an electron from the desired molecule to create a 1+ ion


What are the pitfalls of the process of ionising particles in a mass spectrum?

The excess energy delivered by the electron missile can provide sufficient energy to break covalent molecules, releasing fragment ions of the original molecule.


Why do mass spectra sometimes show tiny peaks with a m/z value just one higher than the M+ peak?

Due to rare isotopes of Carbon (C13)


What is the M+ peak on a mass spectrum?

The peak caused by the positively charged ion of the desired molecule.


What is the peak with the highest abundance on a mass spectrum known as?

The base peak


Give a general equation to show ionisation in a mass spectrum.

X + e- ----> X+ + 2e-