Okay
a) use n-m/M to find moles of the cu(no3)2
use stoichiometry for cu(no3)2: no2 to find the moles of no2
then multiple n(NO2) by 24.79
b) Use c=n/V to find concentration.
Now, this is the part where I am a bit unsure but:
the ratio for NO2: H3O+ is 1:1, because 2NO2: HNO2 + HNO3 = 2NO2: H30+ + H30+ = 2NO2: 2H30+
and so therefore
ratio is 1:1.
then use pH formula.
i might be wrong but hopefully this will give you guidance