Question

compare dipole moment of bf3 and bcl3

Answer 1

In BF3 the structure is more symmetrical. The three angles of B-F are at 120 degrees and all these bonds lie in one plane. The net moment of dipole is zero, as all of them cancels each others dipole moment. Same is the case with BCl3 

Answer 2

Explanation:

Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 u, and so a mole of carbon-12 atoms weighs exactly 0.012 kg.