With carbon dioxide what phase change take place when the temperature decreases from -40c to -80c at 2 atm

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Me i dont know what to do! the table compares the number of electrons in two unknown neutral atoms. comparison of electrons atom number of electrons a 10 d 11 use this information to determine the number of valence electrons in the atoms. which of the following correctly compares the stability of the two atoms? both are unreactive. both are highly reactive. a is unreactive and d is reactive. a is reactive and d is unreactive.

Aconcentrated solution of ammonia is 14.8m and has a density of 0.899g/l. what is the concentration of ammonia in this solution in weight percent (%w/w)?