Question #336a1

2 Answers
Jul 31, 2017

5.018xx10^29 molecules of H_2O

Explanation:

According to mole concept :

1 mole of H_20 = 6.022xx10^23 molecules of water = 18 gram H_20

So 18 grams of H_2O = 6.022xx10^23 no. of molecules H_2O

And

150 grams of H_2O = 6.022xx10^23/"18"xx 150 molecules H_2O

= 5.018xx10^29 molecules of H_2O

Jul 31, 2017

5.016326 * 10^24

Explanation:

To calculate the number of molecules of a substance, we simply multiply the amount of moles by Avogadro's number, which is equal to 6.022 * 10^23

But how many moles are in 150 g of H2O?

Moles = Grams of a substance / Atomic Mass Of A Substance

Moles = 150g / 18.015 (The atomic mass of two H is 2.016. The atomic mass of O is 15.999)

Moles = 8.33 mol

Therefore there are 8.33 * 6.022 * 10^23 molecules. (5.016326 * 10^24)