Lakshmi has a sample of ammonium nitrate open paren NH sub 4 NO sub 3 close paren that has a mass of 40 point 1 0 g She knows that the molar mass of NH sub 4 NO sub 3 is 80 point 0 4 3 2 g over mol To the correct number of significant digits, how many moles of NH sub 4 NO sub 3 does the sample contain?