2007 MJC Prelims Paper 2 FAQs

Explanation for Q3b(ii)
Electron to be removed from K+ is from 3p orbital whereas electron to be removed from the other elements shown is from 4s orbital, which is of higher energy. Hence, K+ has highest 2nd IE.

Explanation for 3d(iv) no. 2
A is unlikely to be HOOC-C(triple bond)C-COOH.
Too difficult to dehydrate (HOOC)CH=C(OH)(COOH). (NOT in syllabus)

Explanation for 4e
K = [butylparaben (organic)] / [butylparaben (aq)] = 1 x 10^3
Partition coefficient is referring to the equilibrium constant, K.

Explanation for 5e
Each "building block" of the protein contains 6 amino acids, which must be linked by 6 amide groups (5 in between + "1/2" at each end).
Hence, 6 molecules of H2O are lost to form one "building block".
Thus, Mr of each "building block" is 2 x 75 + 146 + 3 x 105 - 6(18) = 503.
Each amino acid has one side chain, which is the "residue".