Why are group 17 elements the most reactive nonmetals?

Because as u go across groups the more reactive it is due to the ability of electrons to be given or taken away

.100 mol CO2 x 
using the values of the periodic you first add the masses of C (12.01g) and O (there are two so it'll be 32.00g). That value will give the mass of 1mole of CO2.

I hate to do this, but
http://youtu.be/Pft2CASl0M0 is a link to a mr andersen video. I dislike watching these cause this is what my teacher uses instead of actually having to teach herself.