II B.
- Mr(PCl₃) = Ar(P) + 3 × Ar(Cl) = 31 + 3 × 35.5 = 31 + 106.5 = 137.5
- Mr(K₂CO₃) = 2 × Ar(K) + Ar(C) + 3 × Ar(O) = 2 × 39 + 12 + 3 × 16 = 78 + 12 + 48 = 138
- Mr(Ca(NO₃)₂) = Ar(Ca) + 2 × Ar(N) + 6 × Ar(O) = 40 + 2 × 14 + 6 × 16 = 40 + 28 + 96 = 164
Ответ: Mr(PCl₃) = 137.5; Mr(K₂CO₃) = 138; Mr(Ca(NO₃)₂) = 164.