1.3 Flashcards
What is the ideal gas equation ?
PV = NRT
What are the conditions for the ideal gas equation ?
P= pa
V= M^3
T= K
What is the definition of an isotope ?
Atoms of the same element, with different numbers of neutrons and masses .
What is the mass spectrometer ?
Used to find the relative atomic mass of an element.
1. MASS OF EACH ISOTOPE
2. ABUNDANCE OF EACH ISOTOPE
What are the stages of the mass spectrometer ?
Vaporisation
Ionisation
Acceleration
Deflection
Detection
Describe ionisation (+1)
- bombarded with electrons
- collisions are energetic + knock off electrons
-creating positive ions which are attracted to a negatively charged plate.
Describe acceleration
- electric field accelerates the ions.
- You can increase/decrease the size of the field to detect larger/smaller ions
Describe deflection + the affect of mass
- The electromagnetic field deflects ions by different amounts.
1. lighter ions are deflected more than heavy.
2. ions with a higher charge are deflected more.
Describe detection
- Beam of ions is converted into an electrical signal
-Only ions with correct m/z ratio are detected - Signal is amplified and recorded
What happens to ions with incorrect m/z ratio ?
-Deflected and collide with walls
- Pick up electrons and become neutralised
- removed by vacuum
Equation to calculate atomic mass
sum of {ratio x mass} / total ratio
3 uses of mass spectrometry
- identifying unknown compounds (who knows)
- analysing molecules in space (miss Essex)
- forensic science (mr ross)
What is fragmentation ?
- The splitting of molecules, in a mass spectrometer into smaller parts.
- Molecular ions are energetically unstable.
How many peaks are present on the Cl mass spectrum ? + why ?
5
- chlorine is diatomic (Cl2)
- 35 and 37 are the two isotopes
How do we find the height ?
- we know that cl35 + 3/4
-cl37 = 1/4 - e.g cl37 + cl35 + 1/4 x 3/4 = 3/16
{overall ratio is 9:6:1}
