Chapter 7, Problem 77P

Please explain how to calculate the pH.

I'm having trouble with converting lewis diagrams into VSEPR diagrams. I currently have this example of C2BrCl3 which I want to turn into a lewis structure, but I'm not sure what steps I need to do in order to do so. I have the table written down, however, there's two central atoms so what would I do? There seems to be 4 electron domains on the carbon atom and no lone pairs so it would seem like this shape would be tetrahedral. Here's what I have now. Thanks!

We discussed the solid phase resin using in peptide synthesis. Provide a mechanism, for its formation. DRAW THE MECHANISM.