General Knowledge - Chemistry - Discussion

Here, d = m/v equal to 0.0018 g so we can write as 18 * 10^-4 g.
Then n = 18 *10^-4/18 = 1 * 10^-4.
One mole = 6.022 * 10^23.
1 * 10^-4 mole = x
And the answer is 6.022 * 10^19.

Density of water = 1.

So 1 = mass/volume, 1 = mass/0.0018, mass = 0.0018g no. of mole = weight/molecular

weight = 0.0018/18.

No of water molecules = No of mole*Avogadros no.

= 0.0018/18*6.023*10exp23 = 6.023*10exp19.

Number of mole = Molecule.wt*Avogadros no. Thus by multiplying both we get answer.

In the question the volume of water is given. To relate this we must have to used volume of one mole equals to 22.4 lit rather than gram molecular mass.

Why should taken (6.02 x 10exp19 molecules) molecule, if Avogadro.No is 6.023 x 1023?

Can you explain?

First using the density formula, convert volume to mass then divide the mass substance from molecular weight of compound.

You will get the answer for any molecules.

Here One drop of water has the volume 0.0018 mL.
Because the density of water is 1, the mass is 0.0018 g. The molar mass of water (H2O) is 18.0 grams/mol (1.008 + 1.008 + 16.0). This means there is one mole of water in 18.0 grams. One mole is 6.02 x 1023 molecules.

Then you can convert grams to number of atoms:
0.0018 grams / 18.0 grams x (6.02 x 10exp19 molecules)

Read more: http://wiki.answers.com/Q/How_many_water_molecules_are_in_one_drop_of_water#ixzz1iphXiIJy