Question

If we consider that 1/6 in palce of 1/12,mass of carbon atom is taken to be relative atomic mass unit,the mass of one mole of substance will?

Answer 1

It will Unchanged
If you take 1/6 then 1 amu will correspond to 2 amu. Therefore the number of particles will be Na/2 in one mole. When you multiply Na/2 × 2 amu (mass of 1 mole) you'll get Na × 1 amu only. So mass remains unchanged.