Why was mass lost from the crucible during the reaction?

There are 6.022 x 10^23 atoms of hg in 1 mole of hg. the number of atoms in 4.5 moles of hg can be found by multiplying 4.5 by 6.022 x 10^23 a. 2.7 x 10^24 b. 27 x 10^23 c. 2.71 x10^24 d. 27.099 x 10^23

Drag each number to the correct location on the equation. each number can be used more than once, but not all numbers will be used. balance the equation with the coefficients. 2 3 4 5 kclo3 -> kcl + o2

What is the percent by mass of oxygen in fe2o3