Why the component of the
mixture can be easily be separated by using various physical means

Remember that the substances in a mixture have not combined chemically. They have not turned into new substances, but are still the same substances as before - they have just been physically combined. That is why we can use physical methods to separate them again.

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