One gram of alum, kal(so4)2.12h2o, contains 1.3 × 1021 al atoms. how many oxygen atoms are contained in 1.0 g alum?

From the chemical formula, 1 formula unit of KAl (SO4)2.12H2O encompasses 1 atom of Al = 4 * 2 atoms of O in KAl (SO4)2 + 12 atoms of O in 12H2O which is equal to 20 atoms of O.

So, if you have 1.3 × 10^21 Al atoms, you have 20 * 1.3 × 10^21 O atoms will now be equal to 2.6 * 10^22 atoms of O.

the answer is c.the valence of the atoms combine .