How many water molecule will be dissociated from 550 billion water molecules.?

Question

How many water molecule will be dissociated from 550 billion water molecules.?

Answer 1

550 billion water molecules is

550 x 10 ^ 9 water molecules

this is equivalent to

550x10^9 H2O molecules / 6.023 x 10^23 water molcules = moles of water

9.13 x 10^ -13 moles

Water dissociates according to this reaction

H2O + H2O ----> H3O+  + OH-

Assuming room temperature, the H3O+ concentration will be 1.00x10^ -7 M

this means that out of 1 mol of water molecules ( 6.023 x 10^23) only 1x10^-7 moles of water (6.02x10^16) exists as H3O+

so if you have 9.13x10^ -13 molecules then this mean that only

9x10^ -49 molecules exist as H3O+  

Answer 2

nope...

water dissociates @ 1e-7 moles per liter ,,,,(not per mole)

& you can't have a e-19 or e-49 molecules

===============================

so let's find out the # of litres we are talking about:

fiirst the moles:

550e9 molecules @ 1 mole / 6.022e23 molecules /mole = 9.133e-13 moles H2O  (in the 550 billion molecules)

then the grams:

9.133e-13 moles H2O @ 18.015 g / mole = 1.645 e-11 grams,  (in the 550 billion molecules)

and now the litres:

1.645 e-11 grams @ 1 litre / 1000 grams = 1.645 e-14 litres of water,   (in the 550 billion molecules)

===================

now we use the dissociation of water @ water dissociates @ 1e-7 moles per liter ,,,,(not per mole)

1.645 e-14 litres of water @ 1e-7 moles dissociated per liter = 1.6453-21 moles of water are dissociated  out of the 550 billion water molecules

lastly, if 1.6453-21 moles of water are dissociated  out the 550 billion molecules, how many molecules is that:

1.6453-21 moles @ 6.022 e23 molecules / mole = 991 molecules

that's youe answer: 991 molecules,

but since the 550 billion only had 3 sig figs, you might consider rounding your answer off to 990 molecules