Chapter 17 Key Concepts

Question 1

What does IR do to bonds

Answer 1

Makes them bend or stretch more

Question 2

What affects the amount that a bond stretches or bends

Answer 2

Mass of the atoms in the bond
-heavier atoms vibrate slower than light ones
Strength of the bond
-strong bonds vibrate faster

Question 3

How do greenhouse gases cause global warming

Answer 3

Water vapour CO2 CH4 absorb this longerwavelengh IR radiation cuz has same frequency as their natural frequency of their bond

• eventually the molecule re-emit the energy as radiation that increases Temp of the atmosphere close to the Earths surface leading to global warming
• acceptance of scientific evidence explaining global warming has promoted governments towards policies to use renewable energy supplies

Question 4

What would you use IR spec

Answer 4

To identify functional group
Provide evidence in a court of law of courts eg drink drawing
-monitor gases causing air pollution in CO NO
-modern breathalysers

Question 5

How does IR work

Answer 5

• the sample under investigation is placed inside an IR spect
• beam of IR radiation in the range 200-4000cm-1 is passed through the sample
• The molecule absorbs some of the IR frequencies and the emerging beam of radiation is analysed to identify the frequencies that have been absorbed by the sample
• the IR spectrometer is usually connected to computer that plots a graph of transmittance against wave number

Question 6

How does a breathalyser work

Answer 6

IR based breathalyser pass a beam of IR radiation through the captured breath in the sample chamber and detect the IR absorbance of the compounds in the breath. The characteristic bonds present in ethanol are detected. More IR radiation absorbed the higher the reading the more ethanol