Question

Assuming that you use 8.5g poly (dimethylsiloxane), what mass of boric acid is needed for the cross-linking reaction?

Answer 1

I need more info, as the number of "n" in the poly dimethylsiloxane. If you give me that number, I can easily calculate the molecular mass of this, and then, by stechiometry, we can calculate the required mass.

in the following picture you have the image of this cross linking:

But like I stated above, i need the n number so I can calculate better.

Let me tell you how you'll do it:

the molecular formula for this is CH₃[Si(CH₃)₂O]_nSi(CH₃)₃ so if n = 2 (let's assume this) then it's molecular mass would be:

8*12 + 24*1 + 2*16+ 3*28 = 236 g/mol

calculate the moles of the poly:

moles = 8.5 / 236 = 0.036 moles

this moles are the same of boric acid, so, the molecular mass of boric acid reported is 61.83 g/mol

then the mass = 2.23 g

With the correct number of n, we can actually know the real number.

Hope this at least gives you an idea of how to solve it.