One problem with organic chemistry is that we tend to focus on one molecule at a time, we forget that there are many, many molecules undergoing the reaction. Assume you started with exactly 1 g of bromobenzene, how many MOLECULES OF bromobenzene is this?

1g of bromobenzene = 3.84× 10^21 molecules

Explanation:

Molar mass of bromobenzene (C6H5Br)= 79.9+(12×6)+ 5= 156.9

156.9g(1mole) has 6.023×10^23 molecules

This implies that 1g will contain 6.023×10^23/156.9 = 3.84×10^21 molecules

0.071 mole

Explanation:

As discovered from Avogadro's hypothesis, 1 mole of any substance contains 6.02x10^23 molecules.

This simply means that 1 mole of H3PO4 also contains 6.02x10^23 molecules.

If 1 mole H3PO4 contains 6.02x10^23 molecules,

Then, xmol of H3PO4 will contain 4.3x10^22 molecules i.e

Xmol of H3PO4 = 4.3x10^22/6.02x10^23 = 0.071 mole

From the calculations made above, 4.3x10^22 molecules of H3PO4 have 0.071 mole of H3PO4