AS Exam Questions

Question 1

Two differences between infrared spectrum of COOH and OH other than fingerprint regions

Answer 1

OH of alcohol absorption peak in different place (3250-3550cm-1) to OH absorption peak of COOH (2500-3000)

C=O in acids has absorption peak at 1680-1750

Question 2

Suggest what might cause the relative atomic mass of a sample to be different from the relative atomic mass given in the periodic table

Answer 2

Other isotopes present/ different abundances of isotopes

Question 3

m/z Relative Abundance

124 2
126 8
128 12
130 4

Which m/z value of the ions produces the biggest current when it hits the detector? Why?

Answer 3

128

Most abundant ion

Question 4

The mass spectrum of tellurium has a small peak at m/z = 64

Explain the existence of this peak

Answer 4

2+ ion formed/ 2 electrons removed

From 128 Te

Question 5

Is the atomic radius of 124Te the same as 128Te? Why?

Answer 5

Yes

Same number of protons and same number of electrons