Practice questions mistakes

Question 1

State how the relative abundance of 185Re + is determined in a TOF mass spectrometer [2]

Answer 1

• At the negative plate, the ions gain an e-
• abundance depends on the size of current

Question 2

State how ions are detected and how the abundance of each ion is measured in a TOF mass spectrometer [2]

Answer 2

How ions are detected: each ion gains an e-
How abundance is measured: abundance is proportional to current

Question 3

Mass number definition vs relative atomic mass definition [1]

Answer 3

the NUMBER of protons and neutrons
vs
the average mass of an atom/element compared to 1/12 the mass of an atom of Carbon-12

Question 4

An atom has all its electrons in their lowest energy levels. Which atom contains only 2 unpaired electrons? [1]
Helium
Beryllium
Oxygen
Iron

Answer 4

Oxygen
(bc it has two unpaired electrons in its 2p orbital)

Question 5

What is the electron config of V ^2+ in the ground state? [1]
1s2 2s2 2p6 3s2 3p6 3d3
1s2 2s2 2p6 3s2 3p6 3d1 4s2
1s2 2s2 2p6 3s2 3p6 3d3 4s2
1s2 2s2 2p6 3s2 3p6 3d5 4s2

Answer 5

V: 1s2 2s2 2p6 3s2 3p6 4s2 3d3
but e- is always removed from 4s orbital first so
V ^2+: 1s2 2s2 2p6 3s2 3p6 3d3

Question 6

Titanium contains: 46, 47, 48 & 49 Ti
RAM= 47.8
Abundance 46 Ti:47 Ti:49 Ti= 2:2:1
Calculate the % abundance of 46 Ti [3]

Answer 6

8

Question 7

Which bond has the most unsymmetrical electron distribution? [1]
H-O
H-S
H-N
H-P

Answer 7

H-O
(highest electronegativity difference)

Question 8

Define electronegativity [1]

Answer 8

Electronegativity is a measurement of the ability of atoms to attract a pair of e- in a COVALENT BOND

Question 9

Suggest in terms of the IMF for each compound, why CBr4 has a higher BP than CHBr3

Answer 9

• Both have VDWs
• CBr4 has a higher molecular mass and more e- (so more opportunities for temporary dipoles to be induced)
• so more energy is needed