Balance the equation Ag2O ->Ag + O2​

There are 6.022, 104 atoms of hg in 1 mole of hg the number of atoms in 45 moles of hg can be found by multiplying 4.5 by 6.022, 102 which is the number of atoms in 4.5 moles of hg, correctly written in scientific notation with the correct number of significant figures? 0 21,109 0 21,100 271, 1024 27.099, 100 mark this and retum save and exit submit

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

Which symbol can be used to indicate the pressure at which a chemical reaction is carried out? 25°c 2 atm pa