Question

What is the number of molecules in 1.00 mol of iodine crystals?

Is the answer 6.022 x 10^25 molec. of I2 ? or do I have double this answer, given that I2 is a diatomic molecule??

Answer 1

`6.02 * 10^(23)`

Explanation:

The problem wants to make sure that you are familiar with the definition of one mole of a given substance.

In this case, you're dealing with a covalent compound, so you're looking for the number of molecules of iodine, `"I"_2`, present in exactly `1.00` moles of iodine crystals.

Now, a mole is defined as very, very large collection of particles. In order to have `1.00` moles of iodine crystals, you need to have exactly `6.022 * 10^(23)` molecules of iodine.

`color(blue)(ul(color(black)("1 mole I"_2 = 6.022 * 10^(23)"molecules I"_2` `->` Avogadro's constant

In your case, you will have

`"1.00 moles I"_2 = 6.02 * 10^(23)"molecules I"_2`

The answer must be rounded to three sig figs, the number of significant figures you have for the number of moles of iodine crystals.

Notice that each iodine molecule contains `2` atoms of iodine, `2 xx "I"`, which means that `1` mole of iodine molecules contains `2` moles of iodine atoms.

In `1.00` moles of iodine molecules you have `2` moles of iodine atoms, or

`overbrace(6.022 * 10^(23)color(red)(cancel(color(black)("molecules I"_2))))^(color(blue)(= "1.00 moles I"_2)) * "2 atoms of I"/(1color(red)(cancel(color(black)("molecule I"_2)))) = overbrace(1.20 * 10^(24)"atoms of I")^(color(purple)(="2.00 moles of I"))`

Once again, the answer must be rounded to three sig figs.