Question

How many grams are in 0.02 moles of beryllium iodide, `"Bel"_2` ?

I don't understand physical science, please help me!

Answer 1

`"5 g"`

Explanation:

All you need to do here is to use a conversion factor that can take you from grams of beryllium iodide to moles of beryllium iodide.

As you know, the molar mass of a compound tells you the mass of exactly `1` mole of that compound. Beryllium iodide has a molar mass of `"262.821 g mol"^(-1)`, which means that `1` mole of beryllium iodide has a mass of `"262.821 g"`.

So you can say that you have

`"262.821 g mol"^(-1) = "262.821 g"/"1 mole BeI"_2`

To find the mass of `0.02` moles of beryllium iodide, simply multiply the number of moles by the molar mass in conversion factor form.

`0.02 color(red)(cancel(color(black)("moles BeI"_2))) * "262.821 g"/(1color(red)(cancel(color(black)("mole BeI"_2)))) = color(darkgreen)(ul(color(black)("5 g")))`

The answer must be rounded to one significant figure, the number of significant figures you have for the number of moles present in your sample.