Water molecules?

1mole of water =18g, 1ml=1g at 25degC. Nearly all water molecules but..Ph of water is approx 7 at this temp so using pH=-logbase10 of H/OH concn=10^-7mole/litre or 10^-10mol/ml..gives number of H2O molecules= 6.02x10^23/18 minus 2x10^-10*6.02x10^23=3.344x10^22 just about the same result! Try agen.. 3.344x10^22!

VERY SIMPLE DEAR: LET ME EXPLAIN IT TO U:-

The density of water is = 1g/ml

Volume(given) or water = 1ml

. '. mass of water = d*v = 1g/ml/1ml = 1g

now molecular mass of H2O = 18 g/mol

Since

18g of H2O contains molecules = 6.023*10^23

So 1g of water contain molecules = 6.023*10^23/ 18 = 0.3346* 10^23

= 3.346*10^22 molecules.

Hopes u got it easy.

Since:

H2O atomic mass is 15.9994 + 2*1.00794 = 18.01528 g/mol

1 ml of H2O weighs 1 g

and there are 6.02 x 10^23 molecules/mol

Then:

(6.02x10^23 molecules/mol) x (mol/18.01528g)(1g/1ml H2O)=0.33416x10^23 molecules H2O/ml

=3.34x10^22 molecules H2O/ml

In response to the questions about mole relationships:

No, a mole of water molecules would be water vapor (gas phase) and it would have to occupy 22.4L

It's 6.02x10^23 molecules/atoms of anything.

one mole of a gas occupies 22.4L at STP

and you use atomic mass to go from a given mass to the mole, because the atomic mass is the weight of one mole of the given substance in grams

that said, you would have to use the fact that you have a given volume (1mL) and somewhere have access to the density of water (1g/mL), and then find the mass (which is therefore 1g).

taking that mass, divide it by the atomic mass of water (18.02g/mol), and you have the number of moles.

given the number of moles, multiply by Avogadro's constant, and voila! an answer!

Depends on temperature and pressure. It'd normally be quoted at STP (standard temperature and pressure). 1 atmosphere and 25 Celsius I think (or is it 20?).

Is it really 1 mole (6.02 x 10^23) at STP? I thought that was 1 mole of gas molecules occupying 1 litre at STP.

You got to remember that water has more than water molecules in it. IE. some HO and some free H and O

density >>1mL of H2O = 1 gram of H2O

now use dimentional analysis

1g.H2O x....1 mole H2O......x

.................18.0152 g H2O

6.022E23 molecules = 3.343X1022 molecules

.........1mole water

6.023 X 10^(23) H2O molecules per mL

Density and volume to mass.

Atomic weights to molecular weight to molar weight

How many moles?

Avogadro's number