If 350.0 grams of cr2o3 are reacted with 235.0 grams of elemental silicon, 213.2 grams of chromium metal are recovered. what is the percent yield?

We calculate for the amount of chromium metal in the reactant by,
                            = 350 x (mass of Cr2/mass of Cr2O3) 
                                 = 350 x (104/152) 
                                   = 239.47 grams
The amount of Cr metal in the product is only 213.2 grams. Thus, the percent yield.
                        percent yield = (213.2 grams/239.47) x 100%
                                             = 89%

They are all decomposition reactions.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.