In mass and material balances, when would mass in not equal mass out? (give three possibilities)

What is the number of moles in 15.0 g ash3?

Explain which group an element with the electron configuration 1s2 2s2 2p6 3s2 3p6 3d1 4s2 belongs to.

Compared with the freezing-point depression of a 0.01 m c6h12o6 solution, the freezing-point depression of a 0.01 m nacl solution is