Calculate the molarity of a solution made by adding 35.0 ml of concentrated perchloric acid (70.5 % by mass, density 1.67 g/ml) to some water in a volumetric flask, then adding water to the mark to make exactly 2000 ml of solution. (it is important to add concentrated acid or base to water, rather than the other way, to minimize splashing and maximize safety.)

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles

1.43 x 10^-11 j the guy commented the awnser just making sure u see it .