Q. How many molecules are present in 1 ml of water..? explain

Here, we know that density of water is 1gm/ml.

Hence, 1 gm water will  = 1 ml water.

Now, we have molecular mass of water H₂O = 1x2 + 16 = 18 gm

Since, 1 mol water = molecular mass in gm = 18gm.

As no. of molecules = no. of moles x avogadro's no.

And No. of moles = given mass/ molecular mass.

Here, given mass = 1ml= 1gm

Thus, no. of moles of water in 1 ml = 1/18 mol.

And so No. of molecules in 1ml water = no. of moles x avogadro's no. = 1/18  X 6.022 x 10²³ =0.33 x 10²³ molecules

So, the no. of molecules of water in 1ml of water = 3.3 x 10²²