How to prepare 1M H2O2 using 30% hydrogen peroxide?

Dear Lao,

that's the real issue. All your assumptions may be true.

IMHO is is *absolutely* necessary to specify m/v (mass/volume), m/m or
v/v. It even makes a difference if you (in this case rather
hypothetically as solid H2O2 does not exist [at least for a long
time]) mix 300 ml of H2O2 and 700ml of water, put 300 ml H2O2 in a
beaker and add water up to 1liter or vice versa. Does not make always
a real difference in the outcome of an experiment, but when you need
to troubleshoot a protocol or reproduce an experiment, this kind of
things will drive you nuts. There is nothing like a 'common sense' on
how to make procentual solutions. If possible, always state molar
contents, therefore.

All the best,

Wo

On 5 Feb., 15:45, "WANG XF" <[Only registered users see links. ]> wrote:

In article <[Only registered users see links. ]>, WS <[Only registered users see links. ]> wrote:

Industrial % concentrations tend to be m/m. This is clearly
the case, for example, with concentrated HCl (~ 37% ~ 12M)
or concentrated H3PO4 (85% = 15.2M).

MSDS for 30% H2O2 says "balance water", suggesting
that indeed we are talking about 300 g + 700 g water.
In which case precise molarity calculattion become
troublesome even knowing density of 100% H2O2
because water solutions can change volume
appreciably (e.g. 500 ml ethanol + 500 ml H2O
will result in less than 1000 ml solution).

Not that any of that matters in the experiment in
question! Assuming no volume change and m/m
for 30% and density off 199% of 1.4 g/ml from
Wikipedia, we get 22-28% error depending on the
direction. With the "1 M" being clearly an arbitrary
round number, I wouln't worry about potential
25% error as long as the way the solution is prepared
is clearly stated.

DK