# Question #336a1

Jul 31, 2017

$5.018 \times {10}^{29}$ molecules of ${H}_{2} O$

#### Explanation:

According to mole concept :

1 mole of ${H}_{2}$0 = $6.022 \times {10}^{23}$ molecules of water = 18 gram ${H}_{2}$0

So 18 grams of ${H}_{2} O$ = $6.022 \times {10}^{23}$ no. of molecules ${H}_{2} O$

And

150 grams of ${H}_{2} O$ = $6.022 \times {10}^{23} / \text{18} \times 150$ molecules ${H}_{2} O$

= $5.018 \times {10}^{29}$ molecules of ${H}_{2} O$

Jul 31, 2017

$5.016326 \cdot {10}^{24}$

#### 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 $6.022 \cdot {10}^{23}$

But how many moles are in $150 g$ of $H 2 O$?

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

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

Moles = $8.33 m o l$

Therefore there are $8.33 \cdot 6.022 \cdot {10}^{23}$ molecules. ($5.016326 \cdot {10}^{24}$)