Why does electronegativity increase across a period in the periodic table?

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

Compare and contrast physical changes with chemical changes.

An alkaline battery produces electrical energy according to the following equation. zn(s) + 2 mno2(s) + h2o(l) zn(oh)2(s) + mn2o3(s) (a) determine the limiting reactant if 17.5 g zn and 31.0 g mno2 are used. (type your answer using the format ch4 for ch4.) (b) determine the mass of zn(oh)2 produced. _ g