How many molecules of Barium hydroxide are there in 21.9 grams of barium hydroxide?

Answer 1

Hi Abby!

This problem is dealing with conversions factors. The first thing we have to do is recall the formula of barium hydroxide, Ba(OH)₂.

Now we have to find the molar mass of barium hydroxide. We can do this by adding up the atomic masses of each of the atoms in this compound:

Barium: 137.33 g/mol x 1 (because there is 1 atom of Barium in Ba(OH)₂)

Oxygen: 16.00 g/mol x 2 (because there are 2 Oxygen atoms present in Ba(OH)₂)

Hydrogen: 1.01 g/mol x 2 (because there are also 2 Hydrogen atoms in Ba(OH)₂)

——————————————————————————————————————

(137.33 g/mol) + (16.00 g/mol x 2) + (1.01 g/mol x2) = 171.35 g/mol Ba(OH)₂

So now that we have the molar mass of Ba(OH)₂ we can convert 21.9 grams into moles.

21.9g Ba(OH)₂ 1 mol Ba(OH)₂

——————— x ————————— = 0.128 moles Ba(OH)₂

1 171.35g Ba(OH)₂

Now, to convert from moles to molecules, we will need to use Avogadro's number which is 6.022 x 10²³

0.128 mol Ba(OH)₂ 6.022 x 10²³ molecules

———————— x ——————————— = 7.70 x 10²² molecules

1 1 mol Ba(OH)₂

I hope this helps! Please feel free to reach out for further explanation :)