a) mN2=2*14u=28 u
b) mSO2=32u+2*16u=64 u
c) mH2CO3=2*1u+12u+3*16u=62 u
d) mCu(OH)2=63,5u+2*16u+2*1u=97,5 u
e) mPb3(PO4)2=3*207u+2*31u+8*16u=811 u