What is universal indicator? what is its advantage?

Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom? some uncharged particles are scattered by a gold foil. all uncharged particles are attracted towards a gold foil. all positively charged particles pass straight through a gold foil. some positively charged particles bounce back from a gold foil.

The empirical formula of a compound is ch2o and its mass is 120 amu/molecule, what is its formula?

Calculate the mass of 0.750 mol of the following substance. na3po4. , i'm not quite sure on how to set up the problem to solve! : (