wt% means weight percent which is sometimes written as w/w i.e. [ weight of solute/ weight of solvent*100 = percent of solute in the solution]. In your case 25 wt% of tetramethylammonium in methanol means, there is 25g of tetramethylammonium for every 100g of methanol.

wt% of a species is a common way to refer to the mass fraction of the species times 100.

Mass fraction of a species is the mass of the species divided by the total mass of all species.

So 25 wt% TMAOH in MeOH could be: 25 g TMAOH in 75 g MeOH:

wt% TMAOH = 100x[25 g / (25g + 75g)] = 100 x 0.25 = 25

25 wt% solution of tetramethylammonium hydroxide in methanol means 25g of tetramethylammonium hydroxide in 100g of methanol.

It means weight percent. you can read about weight percent in this link:

http://dl.clackamas.cc.or.us/ch105-04/weight.htm

Quite an interesting question, since we do not know exactly what the chemical background of the original statement was.

I agree with all of my foreposters and say 25g of (powder) substance in 100 g of methanol.

But it might be more difficult or complicated than it seems at first sight!

(since normally I would accept a terminology either to be vol/vol, vol/wt, wt/wt or wt/vol.).

A really correct definition/solution perhaps at the end of my post.

In wikipedia (http://en.wikipedia.org/wiki/Mass_concentration_%28chemistry%29) compare also in subchapter "Usage in Biology" .

see also:

http://en.wikipedia.org/wiki/Percentage_solution_%28disambiguation%29 and

http://en.wikipedia.org/wiki/Mass_fraction_%28chemistry%29

Found @:

>

Found @ https://answers.yahoo.com/question/index?qid=20070816000953AAuAxlV

Found @ http://guweb2.gonzaga.edu/faculty/cronk/CHEM240pub/L01-index.cfm

>

So it might be Peter Sobolewski is right...

Hope this helps to get rid of the problem. Good luck, regards, Wolfgang

Dear all

But what is the meaning of the following

 a suspension containing 2.5 wt% of (A )nanoparticles and 1 wt% of a

block copolymer dispersing agent in xylene

Thank you

Unfortunately, still are conflicts in the use of this therm. Expressing 25 wt.% as 25 g of solute and 100g of solvent, is wrong because the total weight of the solution will be 125 g. Peter Sobolewski explained perfectly in his post:

wt.% = [g solute/(g solute + g solvent)] x 100

I agree with Peter Sobolewski reply. Similar problem you can see here

http://dl.clackamas.edu/ch105-04/weight.htm

I also agree with Peter Sobolewski explanations.

Percent by mass (weight): is the percentage of the ratio of one component mass to the total mass of the solution. (wt. %: wt% signifies weight or mass percentage)

“mass % A (wt. % A) = mass(A) ÷ (mass(A) + mass(B) + mass(C) + ...) x 100”

I agree with Juan I. Sanchez-Avila reply.                                                                                 wt.% = [g solute/(g solute + g solvent)] x 100

Thank you Mr. Juan  

So, its like the percent of dry matter in aqueous solution or other solutions 

Yes, I agree with Ibrahem Khalifa, in solid materials never use the unit mg/l.

One can use another way to represent:

10%w/w means, for instance, 10g of "x" in 100g of a mixture.

Cr16Ni15Mo2MN2TiB

How to calculate mass fraction each isotopes?

25 wt. % solution of tetramethylammonium hydroxide in methanol mean, 25 g of your compound dissolved in 75 g of methanol in order to make 100 g of solution.

thanks guys, i learn a new term today. thanks a lot.

I agree with Anup Kumar Singh 's concept.

HI can anyone help me on how to prepare 25wt% aqueous solution of potassium fluoride ? My lecturer ask me to determine its molarity first by using m1v1=m2v2 but I don't know how to do it. Can anyone explain to me ? I'm still new in this field. Thank you very much.

@Nazmi Asraf Nazri check this.

Hi, 25g of tetramethyl ammonium hydroxide + 75 g Methanol = 25 wt% solution.

Good luck with your research.

If anyone needs to prepare any kinds of solution, please send me a message. I am here to help you all.

I agree with Peter Sobolewski, but disagree with Fatima Zia.

In chemistry, this ratio (wt%) is referred to as "Mass Fraction " and calculated by

Mass of solvent (gm)/Mass of total mixture (gm).

25 wt% TMAOH is thus meant 25 gm of TMAOH / (25 gm of TMAOH + 75 gm of

methanol )

Hi and greeting to everyone,

I am preparing 5%wt of immobilized enzyme (lipase) in 20mL of solvent ,tert-butyl alcohol.Is my calculation here is correct.

1mL=1g then,

20 mL solvent= 20g solvent , thus ,

5%wt=(g enzyme/20g solvent)*100

weight of enzyme (g)= 1 g

Please help me as im new in this field.

I don't understand why literature generate such confusion!

Text book are very clear.

The ratio of w/w % : means gram of solute mixed with a 100 gram of solute/solvent. It depends on the description of mixing.

Or

If the ratio is w/v% that means gram of solute dissolved in 100 ml of the solution (not solvent); or in other words, gram of solute will dissolve first in such quantity of solvent then q.s. to 100mL.

In your situation: You have to scenarios:

A) If you are mixing: 25% w/v that means: 25 g of your solute (in this case is tetramethylammonium hydroxide) will be dissolved in such quantity of methanol (e.g., 70ml methanol), then, stir the material until all the solute dissolved and finally q.s. to 100mL using methanol. (note: use volumetric flask for accuracy). That's it. Very easy and simple by just adding one letter. W/V%.

B) If you are mixing: 25% w/w that means:

25 g of your solute (in this case is tetramethylammonium hydroxide) will be dissolved in such quantity of methanol that suppose to weigh a 100g.

Now. How would you weigh a solvent?!

1) Use the density of the solvent in order to figure out How much (mL) of methanol corresponding to 100g of methanol. e.g., 0.791 g/mL at 25ºC according to Sigma: https://www.sigmaaldrich.com/chemistry/solvents/methanol-center.html

Now that would be 79.1 mL for a 100g of methanol. Did you notice the difference in mL of methanol compare to part A?!

That means you would mix 25 g of your solute (in this case is tetramethylammonium hydroxide) in 79.1 mL of methanol. This is called 25%w/w compare to 25% w/v.

2) another way to weight the methanol, use an empty beaker, tare the balance and weigh methanol until you get 100g. Then use that volume to dissolve 25g of your solute.

Note: keep in mind the lose of methanol (evaporation). So do the weighing and mixing quickly and carefully and cover your material otherwise you are changing the ratio of mixing.

Last part would be: if the ratio is v/v% that means such quantity of solvent will be mix with another quantity of solvent then q.s. to 100 mL. e.g,, 5% v/v ethanol in water. That means 5 mL of ethanol will be mixed in such quantity of water (e.g., 90 ml), then, q.s with water up to 100mL. because sometime when you mix to solvents, the volume capacity will vary based on the interaction in the molecular level! that's why we always start with some quantity then, q.s. up to 100.

Anup Kumar is right

I want to prepare 1, 2 and 3 wt% of Activated carbon to mix with Polyurethane foam. How do i prepare the samples?

Concentrations are typically given in a solute to solution basis; not in a solute to solvent basis. A rare exception to this trend is molality (mol solute / kg solvent). Such wt% concentrations (solute to solution basis) should not be confused with wt/wt 'formulation ratios' (solute to solvent basis). Formulation ratios may apply to suspensions or dispersions; not just to solutions.

So; in terms of solution conncentration, as seemingly is intended in this query enunciate; the mentioned wt% tetramethylammonium hydroxide (TMAH) should be understood as (g TMAH / g solution)·100%.

25 wt. % solution of tetramethylammonium hydroxide (TMAH) in methanol should hence be understood as (mass of TMAH / mass of solution)·100%; with mass of solution = mass of TMAOH + mass of methanol.

it means that 25 gram of tetramethylammonium hydroxide (solute) dissolved in 100 ml of methanol (solvent)

Unfortunately, that is an ambiguous and non-scientific way of reporting concentration that most of the suppliers use. From the metrological point of view, "25% wt in a solvent" is just wrong. One should determine w/v or w/w. Abdulkareem Alanezi already explained it nicely and clearly in the above comments.

To be sure, one may do titration against an acid, such as HCl.

So 25 wt% TMAOH in MeOH could be: 25 g TMAOH in 75 g MeOH:

wt% TMAOH = 100x[25 g / (25g + 75g)] = 100 x 0.25 = 25

I agree with Emad H. Hussein's answer.

how to convert 10mg/l to wt. % ?Anyone reply help me to convert?

25 gms of tetramethylammonium hydroxide in 100 ml methanol

The answer of Fatima Zia from April 25, 2014 is wrong ( I wonder how she got 30 recomandations. ) She wrote: "wt% means weight percent which is sometimes written as w/w i.e. [ weight of solute/ weight of solvent*100 = percent of solute in the solution]. In your case 25 wt% of tetramethylammonium in methanol means, there is 25g of tetramethylammonium for every 100g of methanol."

The usual meaning of 25 wt% of tetramethylammonium in methanol is 25g of tetramethylammonium in 75g of methanol (total weight of the solution is 100g).

This simply means there is 25 g of tetramethylammonium in every 100g of methanol .