Arrange the bases

I) deuterated ammonia (ND3)
Kb = 1.1 × 10−5;
II) hydrazine (NH2NH2) Kb = 1.7 × 10−6;
III) hydroxylamine (NH2OH)
Kb = 1.1 × 10−8;
IV) ammonia (NH3) Kb = 1.8 × 10−5;
in decreasing order of strengths.

To arrange the bases in decreasing order of strengths, we need to compare their equilibrium constants for the reaction of the base with water. The higher the equilibrium constant (Kb), the stronger the base.

Here are the given values of Kb for each base:

I) deuterated ammonia (ND3) - Kb = 1.1 × 10−5
II) hydrazine (NH2NH2) - Kb = 1.7 × 10−6
III) hydroxylamine (NH2OH) - Kb = 1.1 × 10−8
IV) ammonia (NH3) - Kb = 1.8 × 10−5

Comparing the values, we see that:

IV) ammonia (NH3) - Kb = 1.8 × 10−5 (highest Kb)
I) deuterated ammonia (ND3) - Kb = 1.1 × 10−5 (second-highest Kb)
II) hydrazine (NH2NH2) - Kb = 1.7 × 10−6 (third-highest Kb)
III) hydroxylamine (NH2OH) - Kb = 1.1 × 10−8 (lowest Kb)

So, arranging the bases in decreasing order of strength:

Ammonia (NH3) > Deuterated ammonia (ND3) > Hydrazine (NH2NH2) > Hydroxylamine (NH2OH)