Question

how many molecules are present in 9 gram of water ?​

Answer 1

Molecular weight of water = 18g

Given weight = 9g

No. of mole = given weight ÷ molecular weight

So, moles of water = 9÷ 18 = 0.5 mol

1 mol contains 6.022 x 10^23

0.5 mol contains 6.022 x 10^23 ÷2

= 3. 011 x 10^23.

Answer 2

Given :

Mass of water = 9 gm

To Find :

Number of molecules present in 9 grams of water

Solution :

We know, one mole of water has a mass of 18 gm.

So, molecules present in 1 mole of water i.e, in 18 gm of water is 6.022×10²³.

So,

18 gm of water contains 6.022×10²³ molecules

1 gm of water will contain $\frac{6.022 * 10^2^3}{18}$ molecules

9 gm of water will contain $\frac{6.022 * 10^2^3}{18}$×9 molecules

                                         = 3.011 × 10²³ molecules.

Therefore, 3.011 × 10²³ molecules are present in 9 grams of water.