The Molar Mass of Cocaine Hydrochloride is 12*17 + 1*22 + 35.5 + 14 + 16*4 which equals to 339.5 Grams Per Mole.

You have 24.5 Milligrams which equals to 0.0245 Grams.

Number of Moles = “Grams” divided by “Molar Mass”

Hence:

Number of Moles = 0.0245/339.5 = 7.22 multiplied by 10 to-the-power-of -5

In numbers, that is 0.0000722 Moles you’ve got.

Number of Particles of that Cocaine stuff is 0.0000722 multiplied by Avogadro’s Constant which is “6.0221415 times 10^23”.

0.0000722 x 6.0221415 x 10^23 = 4.35 multiplied by 10 to-the-power-of 19 which is a pretty big number!

Finally, to calculate how many ATOMS you have, you have to multiply the number of PARTICLES you have by the number of ATOMS PER PARTICLE. Each molecule of that Cocaine stuff has 17 + 22 + 1 + 1 + 4 particles which is 45 particles.

Hence, you’ve got 4.35 x 10^19 x 45 worth of atoms in your sample which equates to 1.96 x 10^21