How many As atoms are there in a 35.7 gram sample of As ?

Answer 1

Hello Rafael:

In this problem, we need the Avogadro's number, which states that the number of representative particles contained in one mole of a substance equal to 6.02 x 10²³ particles. In this case: atoms. From the periodic table, the atomic mass of As is 74.922.

First, we calculate the number of moles of As equivalent to 35.7 grams as follows:

mole As = gram As x 1 mole/Atomic mass As

mole As = 35.7g x 1 mole/74.92 g = 0.4765 mole

Number of atoms in 0.4765 mole As = 0.4765 mole x 6.02 * 10²³ atoms/1 mole

= 2.87 * 10²³ atoms

Therefore, the number of As atoms in the 35.7 gram sample of As is 2.87 x 10²³.

Answer 2

Hi Rafael!

In this problem we will be working with conversion factors. The first step in solving this problem is to convert grams of arsenic into moles of arsenic. To do this, we will need to find the molar mass by looking at the periodic table. I found it to be 74.92g/mol. Now we can take our given of 35.7 grams and convert it into moles:

35.7g As 1 mol As

———————— x —————— = 0.477 moles As

1 74.92g As

Next, we need to convert our moles of arsenic into molecules. We will do this by using Avogadro's number which is equal to 6.022 x 10²³ molecules. This conversion should look like this:

0.477 mol As 6.022 x 10²³ molecules

—————— x ——————————— = 2.87 x 10²³ molecules As

1 1 mol As

I hope this helps! Please contact me if you need any further explanation :)