Mass Spectrometry & IR

What do the heights of the peaks represent in the mass spectrum?

• number of isotopes
• relative abundance of each isotope
• average atomic mass
• charge:mass ratio

A sample of pure chlorine gas is analyzed in the MS. Which of the following is a correct interpretation?

• Chlorine has an isotope with a mass of 70 amu
• Chlorine has three known isotopes
• Chlorine is diatomic
• Chlorine is highly reactive

What is the average atomic mass for this element?

• 10 amu
• 10.8 amu
• 19.9 amu
• 11 amu

Where is the base peak?

• 57 amu
• 29 amu
• 72 amu
• 43 amu

Which of the following statements best describes the base peak in a mass spectrum?

• The peak from the most stable radical.

• The peak of highest intensity.

• The peak from the molecule minus an electron.

• The peak from the species that has the isotope with the highest atomic number.

If the molecular ion, M⁺ m/z = 136 and M+2⁺ at m/z = 138 of approximately equal intensity, which molecule is it?

• C₆H₁₃OCl

• C₁₀H₁₆

• C₉H₁₂O

• C₄H₉Br

The amount of energy in electromagnetic radiation is related to the frequency and wavelength of the radiation. High energy radiation like gamma rays is of:

• low frequency and short wavelength

• high frequency and short wavelength

• high frequency and long wavelength

• low frequency and long wavelength

The amount of energy in infrared light corresponds to:

• the amount of energy needed to promote one electron from a

  bonding to an antibonding molecular orbital

• the amount of energy needed to increase certain molecular

  motions, such as bond vibrations, in organic molecules

• the amount of energy needed to strip a molecule of one electron to generate a cation radical

• the amount of energy needed to "flip" the spin of a 13C or 1H nucleus

Examining the infrared spectrum of a compound allows us to:

• determine the types of functional groups present in the compound

• determine the nature of the conjugated pi electron system in the compound

• determine the molecular weight of the compound

• determine the carbon-hydrogen framework of the compound

Tags

NGSS.HS-PS4-3

What is the infrared bond type for C−C, C−O, C−N, and C−X single-bond vibrations.

• 4000 to 2500 cm⁻¹

• 2500 to 2000 cm⁻¹

• 2000 to 1500 cm−¹

• below 1500 cm⁻¹