What is the oxidation state of an individual nitrogen atom in nh4oh ? express the oxidation state numerically (e.g., +1)?

In NH4OH, the compounds that make it up are NH4+ and OH-
Therefore N exists in the ammonium form.
In the ammonium ion 4H atoms are connected to N. 
 N is more electronegative than H, therefore when H bonds to N, H is the more positive atom therefore each H has a charge of +1, since there are 4 H atoms the charge contributed by the 4H atoms are +1 * 4 = +4
the overall charge of NH4 is +1
Charge of N (+) +4 =  +1
Charge of N = +1 - 4
Therefore oxidation state of N in NH4 is  = -3

The heat loss Q = 1.6 KJ

Explanation:

Mass of the ice = 71 gm

Heat of fusion for water is ΔH = 6.02

No. of moles of ice

n = 0.266

Now Heat loss is

Q = ΔH × n

Q = 0.266 × 6.02

Q = 1.6 KJ

Therefore the heat loss Q = 1.6 KJ