One difference between mixtures and pure substances is that a) mixtures can be physically separated. b) mixtures are made of one type of atom. c) pure substances have no chemical bonds. eliminate d) pure substances can be physically separated.

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

the maximum mass of nh3 is nh3 in grams