[VRB]

hi!

I want to prepare 1M of orthosilic acid solution by dissolving tetramethyl-orthosilicate (TMOS - liquid reagent) in 1 mM HCl to a final concentration of 1M.

 

Doubt: I don't know how to calculate the volume of TMOS that I need to add in 1 mM HCl in order to have a final cocentration of 1M. I guess that i need to calculate the molarity of TMOS Stock through density (1.023 g/mL), percentage ( >=99%) and mass molecular (152.22 g/mol).
But after this, I don't know how to calculate de volume of TMOS.

 

Can you help me?

 

thanks!

[Arkcon]

After you take all of that into account, you will have the volume needed.  So, first things first.  You want a 1 M solution of TMOS.  How many grams is that? How is density defined?

[VRB]

I don't know if I understand your question.
So, I calculated the molarity of TMOS stock solution: M= ( 0,99 x 1023 g/L)/ 152,22 g/mol = 6,65 mol/L

And now I don't know how to calculate the volume of TMOS (liquid reagent- stock) that  I need to add in 1 mM in order to have a final concentration of 1 M.

Is correct i used the equation of dilutions In this case? Mi x Vi= Mf x Vf. ( Mi= 6,65 mol/L and Mf= 1 mol/L)
=/
Don't know if it is correct because I am used HCl ( 1 mM), and not water. ...

[Arkcon]

So far, so good.  You know how many moles of TMOS.  And you can use M1V1=M2V2.  But ... how much is one mole of TMOS?  I know how much a dozen is, 'cause I can count them.  Humans can't count moles, not of molecules, at any rate.  How would you know you had a mole of sodium chloride, as an example?

[VRB]

so...  then at least how should I calculate the volume of TMOS?

[Arkcon]

Baby steps ... you need molarity, so you have to find moles per liter.  But how much of a substance is 1 mole?  And the easiest answer to that won't be in until of volume of liquid.  Fortunately, units of volume of liquid is a term in the formula for density, the answer to which is a value that you do have.  So ... what's missing?  And can you pull it all together?

I hope you've had a chance to read the Forum Rules{click}.  We don't give complete answers on this forum, we like to help, but we want to see where you're going wrong.