Spectroscopy and Synthesis

Question 1

Describe what an infrared Spectroscopy graph looks like

Answer 1

X-axis is wavenumber in cm^-1
Y is transmittance (amount of radiation that passes through)
The waver number increases from right to left

Question 2

Describe what the different parts of an infrared spectroscopy graph

Answer 2

1. Left hand side above 1500, there are few absorption so it is easy to interpret.
2. Right hand side is called the fingerprint region- there are lots of absorption so it an be difficult to interpret

Question 3

Explain the meaning to the term greenhouse effect

Answer 3

Warming of the atmosphere due to the trapping of IR by absorption by molecular bonds.

Question 4

What are the three most important gases in the Earth’s atmosphere

Answer 4

CH4, CO2, H2O

Question 5

Explain on a molecular level how the greenhouse gases trap heat close to the Eart’s surface

Answer 5

1. Heat (IR) is released from the planets surface.
2. The IR is absorbed by the molecular bonds which vibrate
3. The IR is then re-released
4. Some will continue into space but some is reflected back to the surface keeping the surface warmer

Question 6

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

Answer 6

1. The energy absorbed by the bonds

2. The concentration of absorbing molecules in the atmosphere

Question 7

Why can the term global warming be misleading

Answer 7

Because it suggests that everywhere is warming up. However in some locations climate change will result in cooling.

Question 8

Write 3 consequences of global warming

Answer 8

1. Climate change
2. Sea levels rising
3. Increased incidents of extreme weather

Question 9

Outline some ways in which nations are attempting to reduce excessive greenhouse and its consequences

Answer 9

1. Reduce release of greenhouse gases- reduce car emissions
2. Increased use of renewable energy sources/low carbon more efficient energy use
3. More efficient car engines

Question 10

Write down 3 pieces of information a mass spectrum of an element can tell you

Answer 10

1. Number of isotopes
2. The relative mass of each isotope
3. The relative abundance of each isotope

Question 11

What does m/z value on the x-axis of a mass spectrum

Answer 11

1. Mass to charge ratio

Question 12

What peaks would you expect to see on a mass spectrum of organic compounds

Answer 12

1. The m+ ion (molecular ion) which represents the molecular mass of the molecule
2. There might be an m +1 ion which is much smaller than the m+ ion than molecular ion and one more mass than it.

Question 13

Write balanced equation showing the ionisation of the following molecules to for the molecular ion

Answer 13

pentane + e- → [pentane]+ + 2e-

Question 14

Write equation to show formations of ion with m/z value of 71 from the hexane

Answer 14

[hexane] + → [pentane]+ +CH3

Question 15

What does infrared radiation cause

Answer 15

It causes covalent bonds to vibrate more and absorb energy