Arrange the following:
(i) In decreasing order of the `pK_(b)` values:
`C_(2)H_(5)NH_(2),C_(6)H_(5)NHCH_(3),(C_(2)H_(5))_(2)NHandC_(6)H_(5)NH_(2)`
(ii) In increasing order of basic strength:
`C_(6)H_(5)NH_(2),C_(6)H_(5)N(CH_(3))_(2),(C_(2)H_(5))_(2)NH andCH_(3)NH_(2)`
(iii) In increasing order of basic strength:
(a) Aniline, p-nitroaniline and p-toluidine
(b) `C_(6)H_(5)NH_(2),C_(6)H_(5)NHCH_(3),C_(6)H_(5)CH_(2)NH_(2)`
(iv) In decreasing order of basic strength in gas phase:
`C_(2)H_(5)NH_(2),(C_(2)H_(5))_(2)NH,(C_(2)H_(5))_(3)NandNH_(3)`
(v) In increasing order of boiling point:
`C_(2)H_(5)OH,(CH_(3))_(2)NH,C_(2)H_(5)NH_(2)`
(vi) In increasing order of solubility in water:
`C_(6)H_(5)NH_(2),(C_(2)H_(5))_(2)NH,C_(2)H_(5)NH_(2^.)`

Explanation

To solve the question step by step, we will analyze each part separately.

### Part (i): Decreasing order of `pK_b` values
Given compounds:
1. `C2H5NH2` (ethylamine)
2. `C6H5NHCH3` (aniline methyl derivative)
3. `(C2H5)2NH` (diethylamine)
4. `C6H5NH2` (aniline)
...